Outdoor Fitness Training Framework Main Page

This article is organised as follows:

  • Part 01: Background to Warming-up and Cooling-down.
  • Part 02: The Warm-up (or .
  • Part 03: The Cool-down.
  • Part 04: ROM, Mobility, Flexibility and Stretching.
  • Part 05: Miscellaneous.

PART ONE: BACKGROUND

1.0     Introduction

“A warm-up that consists of a minimum of 5 to 10 minutes of low- to moderate-level activity is essential.” (Bushman, 2017, p.88).

This article provides an overview of the warm-up and cool-down routines that are commonly integrated into a well-planned and structured training programme.

As both a fitness professional and participant I have seen many varieties of both the ‘warm-up’ and the ‘cool-down’, ranging from extremely well-planned and executed warm-ups to the exceedingly boring and unimaginative never ending circle of warm-up doom (the one where the fitness instructor makes you run around in a circle for ten minutes, with the only fun bit being a change in direction!).

Although this article is entitled warming-up and cooling-down, it is also concerned with ROM (range of motion), mobility, flexibility, and stretching, and how they correlate to these two routines.

Much has been written over the years in relation to different forms of stretching and there is still disagreement to this day with regards to the best form of warming-up and cooling-down (Kurz, 2003; Norris, 2007; Kovacs, 2009; Anderson and Anderson, 2010; Walker, 2011a).

However, the purpose of this article is to provide the reader with an overview of the definitions, key principles and differences between the concepts.

Although there are many views on the purpose and aims of the concepts you are about to read, there are many common points.

1.1     Training Session Segments

Whether you are fitness professional-led, solo training, or training in/with a group, there are three parts to a training session:

  1. The Warm-up: In a UK military session this would last approximately 10 minutes.
  2. Main Theme: In a UK military session this would last approximately 40 minutes.
  3. Cool-down: In a UK military session this would last approximately 10 minutes, and would include stretching exercises.

As the reader will notice, within the UK military system, warming-up and cooling-down plays an important role in the physical training of military personnel because of its benefits to performance enhancement and injury prevention.

The American College of Sports Medicine (ACSM) identifies five components to a fitness training session (Bushman et al, 2014, p.343):

  1. Warm-up: At least 5 to 10 minutes of low- to moderate-intensity cardiorespiratory and muscular endurance activities.
  2. Conditioning: At least 20 to 60 minutes of aerobic, resistance, neuromotor, and/or sports activities (exercise bouts of 10 min are acceptable if the individual accumulates at least 20 to 60 minutes of daily aerobic exercise).
  3. Cool-down: At least 5 to 10 minutes of low- to moderate-intensity cardiorespiratory and muscular endurance activities.
  4. Flexibility: At least 10 minutes of stretching exercises performed after the warm-up or cool-down phase.
  5. When indicated, neuromotor exercise training.

Due to client time constraints, some fitness professionals combine the cool-down and flexibility components into one component. Neuromotor exercise training, more commonly known as functional training, is generally delivered as a separate session.

PART TWO: THE WARM-UP

2.0     Introduction

“A warm-up that consists of a minimum of 5 to 10 minutes of low- to moderate-level activity is essential.” (Bushman, 2017, p.88).

The warm-up, also known as physical preparation or movement preparation, is one of the most important elements of an exercise programme, and is particularly prevalent in the prevention of injury. However, the general rule is, the more demanding and intense the session, the longer the warm-up. Sprinters can spend an hour or more warming up – not only working on raising heart rate and body temperature, but also honing neuromuscular pathways (the link between the muscular and nervous systems), thereby increasing the speed and efficiency of muscle contraction.

The objective of the warm-up is to raise total body temperature and muscle temperature to prepare the entire body for vigorous activity, which can aid in preventing injury and enhancing performance. The warm-up period prepares the cardiovascular system, respiratory system, nervous system and the musculoskeletal system by gradually increasing the demand on those systems so that they are able to accommodate the demands of more strenuous activity.

The reader should also note there are there are four key elements, or parts, which should be included to ensure an effective and complete warm up (Walker, 2011a):

  1. The general warm up;
  2. Static stretching;
  3. The sports specific warm up; and
  4. Dynamic stretching.

Opinion is divided as to whether static stretching pre-exercise is beneficial in regards to injury prevention (although research suggests no (Small et al., 2008)) – but dynamic movements such as hip circles, lunges, knee lifts and leg swings may be useful as long as they are done in a controlled and gentle manner – no jerking or bouncing. The exerciser should only do these after they have warmed up. For a steady run, the exerciser could simply start at a slow jog and work up to their usual pace. If conducting an intense session, like hill training or intervals, try some mobility exercises to mobilise the joints.

There is also evidence that the inclusion of additional static stretching during a warm-up may reduce sprinting and jumping performance (Taylor, 2008; Bishop, 2009), but does not appear to change tennis serve performance (Knudson et al., 2004).

Opinion on the causes of these reductions varies between researchers (Kokkonen et al., 1998; Avela et al., 1999; Knudson, 2001).

“It is concluded that dynamic warm up exercises may be a more viable method for enhancing endurance than stretching.” (Kaur et al., 2008, p.101).

2.1     What is a Warm-up?

In simple terms, a warm-up is a session which takes place prior to conducting physical activity (i.e. the main theme), and usually consists of mobility (or joint rotations) combined or followed by light cardiovascular (pulse-raising or aerobic activity) exercises, and stretching exercises.

The general consensus is to conduct joint rotations followed by aerobic activity, followed by stretching (if utilised).

A warm-up is designed to raise your body temperature, heart rate and breathing rate, to mobilise your joints and ‘wake up’ the neuromuscular (nerve to muscle) pathways to prime your body for the specific activity it is about to undertake.

The warm-up is also a good opportunity for an individual to prepare themselves mentally for the game/event/session to come and for a team to work together prior to the start of a game/event/session. Warm-ups can also be used to practice skills and team drills.

2.2     The Purpose of Warming-up

Experts agree that the main purpose of warming-up is to increase the blood circulation in order to raise both the general body and deep muscle temperatures, which in turn help to heat up the muscles, ligaments and tendons in preparation for more vigorous activity. A ‘proper’ warm-up provides many benefits due to the elevated temperatures associated with it. The likelihood of injury is reduced and performance can be improved. The warm-up:

  • Increases muscle efficiency;
  • Reduces potential for muscle pulls and other injuries;
  • Improves reaction time; and
  • Improves the speed of movement of muscles and ligaments.

The higher temperatures and increased blood flow resulting from warm-up are important for delivery of oxygen to the muscles and for prevention of build-up of unwanted waste products which can lead to post exercise muscle soreness.

To this end the basic aims of warming-up are:

  1. Mental Readiness: Prepare the mind mentally for the workload about to be undertaken.
  2. Physical Readiness: To raise the heart rate above resting levels (which enables the heart and lungs to supply oxygen to the working muscles efficiently).
  3. Injury Prevention: To promote blood flow to the extremities and warm the muscles (which makes the muscles more pliant and joints mobile allowing better movement and reducing the risk of injury).
  4. Performance enhancement.

In professional and elite sport environments, using warm-ups to serve these four primary purposes appears to now be very common. As a consequence, warm-ups have evolved to also serve as a method of enhancing performance and reducing or preventing the occurrence of injury.

In UK military training, the warm-up is usually limited to around 10 minutes, and is broken down into the following stages:

  1. Mobility exercises: these gentle movements are all performed while stationary, and their purpose is to mobilise all the major joints of your body.
  2. Pulse-raising activity: this initial pulse-raiser uses large muscle groups in repetitive movements to get your heart beating faster and to raise your body temperature. It can be done indoors, such as marching on the spot, or outside by walking forwards, then gradually building up to a gentle jog over a 3-4 minute period.
  3. Specific mobility exercises: the content of this warm-up segment depends on whether you are about to go for a run, workout with weights or take part in a kickboxing class. The exercises involved should take your joints through a similar range and direction of movement as the activity. For example, to warm up your trunk for a core conditioning workout, you might mobilise the area by arching and rounding the back from an all-fours position.
  4. Final pulse-raiser: in this final warm-up stage, you further raise your heart rate and body temperature by working at a progressively faster pace. Ideally, this should be the activity you are about to perform. For example, if you are going for a run, your final pulse-raising activity should be jogging, with the pace gradually building up to your usual exercise intensity. Avoid a time lag between your warm-up and your main activity otherwise many of the benefits will be lost.

The last part of the warm-up should be devoted to performing movements that are a ‘watered-down’ version of the movements that will be performed during the training session/event/competition. For example, this could involve rehearsing specific movements, at a reduced intensity, that an athlete will use during their competition. Sport-specific activities improve coordination, balance, strength, and response time, and may reduce the risk of injury.

Mobility exercises should include the:

  • Fingers and knuckles.
  • Wrists.
  • Elbows.
  • Shoulders.
  • Neck.
  • Core:
    • Trunk and waist.
    • Spine lateral.
    • Spine front and back.
    • Spine rotational.
  • Hips.
  • Legs.
  • Knees.
  • Ankles.
  • Toes.

Circular movements should be used, in both clockwise and anticlockwise motions. A minimum of three minutes to conduct this part of the warm-up (approximately 5 minutes is the norm).

Cardiovascular (pulse-raising) exercises can include:

  • Jogging.
  • Jumping.
  • Skipping.
  • Sprinting.
  • Aerobics.
  • Practising team drills.
  • Practising basic skills.

You should engage in at least five minutes of aerobic activity for this part of the warm-up (with approximately 5 minutes being the norm).

A total of 8 minutes for both parts of the warm-up is the absolute minimum, with approximately 10-15 minutes being the norm.

2.3     The Benefits of Warming-up

There a variety of benefits including:

  • Release of adrenaline;
  • Increased heart rate;
  • Enabling oxygen in the blood to travel with greater speed and at a higher volume;
  • Increased production of synovial fluid located between the joints to reduce friction;
  • Efficiency of joints;
  • Dilation of capillaries Increase of temperature in the muscles;
  • Decreased viscosity of blood;
  • Facilitation of enzyme activity;
  • Encouragement of the dissociation of oxygen from haemoglobin;
  • Decreased viscosity within the muscle;
  • Greater extensibility and elasticity of muscle fibres;
  • Increased force and speed of contraction;
  • Increase of muscle metabolism;
  • Supply of energy through breakdown of glycogen;
  • Increase in speed of nerve impulse conduction;
  • Removal of lactic acid; and
  • Increased respiratory rate.

2.4     Passive Warm-ups

The main goal of a passive warm-up is to increase body temperature, either total body temperature or local body temperature, without physical activity. In passive warm-up the body temperature is usually increased by some external means, such as wearing heavy apparel, like a sweatshirt, and/or a massage with a topical exercise rub, such as Ben-Gay. One of the advantages of using a passive means of warm-up is that energy is not expended in the warm-up activity. However, for best results it is recommended that a passive warm-up be used in combination with an active warm-up.

2.5     Active Warm-ups

Broadly, active warm-ups are composed of two types:

  • The general or non-specific warm-up utilises low intensity movements such as walking or slow jogging. A general warm-up, involving low level activity, is usually more effective than passive warm-up in increasing deep muscle temperature.
  • Specific warm-up exercises involve the actual body parts that will be used in the subsequent competitive event/training session. For example, swinging a tennis racket in a practice stroke. The advantage of the specific warm-up is that the temperature is more effectively increased in the specific body parts that are to be used.

In 2007, Vetter compared the effects of six warm-up protocols, with and without stretches, on two different power manoeuvres: a 30-m sprint run and a vertical countermovement jump (CJ). The six protocols were:

  • Walk plus run (WR);
  • WR plus exercises including small jumps (EJ);
  • WR plus dynamic active stretch plus exercises with small jumps (DAEJ);
  • WR plus dynamic active stretch (DA);
  • WR plus static stretch plus exercises with small jumps (SSEJ); and
  • WR plus static stretch (SS).

Twenty-six college-age individuals (14 men and 12 women) performed each of six randomly ordered exercise routines prior to randomly ordered sprint and vertical jump field tests; each routine and subsequent tests were performed on separate days.

A 2 x 6 repeated measures analysis of variance revealed a significant overall linear trend (p < or = 0.05) with a general tendency toward reduction in jump height when examined in the following analysis entry order: WR, EJ, DAEJ, DA, SSEJ, and SS.

The post hoc analysis pairwise comparisons showed:

  • The WR protocol produced higher jumps than did SS (p = 0.003 < or = 0.05); and
  • DAEJ produced higher jumps than did SS (p = 0.009 < or = 0.05).

There were no significant differences among the six protocols on sprint run performance (p > or = 0.05). No significant interaction occurred between gender and protocol. There were significant differences between men and women on CJ and sprint trials; as expected, in general men ran faster and jumped higher than the women did.

This research suggests that a warm-up including static stretching may negatively impact jump performance, but not sprint time.

2.6     The RAMP Method

RAMP is a framework or protocol, developed by Dr. Ian Jeffreys, which allows for activities to be easily classified and constructed in the following warm-up sequence:

  1. Raise.
  2. Activate and Mobilise.
  3. Potentiate (or Performance).

It should be the aim of the exercise professional to have individuals fully prepared, both mentally and physically, following the end of the third phase (i.e. potentiation) of the RAMP method and ready for competition or activity. Each of the three phases of the RAMP method plays an important role in the individual’s preparation.

  • Phase 1, Raise:
    • The aim of the ‘raise’ section is too increase:
      • Body temperature;
      • Heart rate;
      • Respiration rate;
      • Blood flow; and
      • Joint viscosity.
    • This section of the warm-up may include low-intensity, multi-directional movements or dynamic range of motion exercises which will be abundant during the training session.
    • Some examples of raise exercises may include:
      • Sprint technique drills (A-skips, B-skips, Bicycles, Heel cycling, Waterfalls.
      • Planned change of direction drills.
      • Squatting, lunging, or crawling.
  • Phase 2, Activate and Mobilise:
    • The aim of this phase of the warm-up is two-fold:
      • Activate key muscle groups; and
      • Mobilise key joints and ranges of motion used in the sport or activity.
    • During this phase of the warm-up, typical activation and mobilisation movements include:
      • Mini-band routines;
      • Balance work;
      • Superman’s and inchworm’s;
      • Squats and lunges;
      • Sumo shuffles;
      • Spinal mobility exercises (flexion, extension, lateral flexion, and rotation).
    • Use generic group movement exercises followed by individual preparation requirements.
    • When designing the activation and mobilisation phase, it is essential the exercise professional carefully considers the fundamental movements and demands imposed by that particular sport or activity.
    • Exercise professionals should develop numerous exercises that activate and mobilise the same key muscles, joints, and ranges of motion which can be used for training variability to prevent monotony and emphasise performance improvements.
    • In addition, some exercises may irritate or be painful for some individuals, so having an assortment of backup exercises for the same joints and muscle groups is vital.
  • Phase 3, Potentiation:
    • The aim of this phase is to ‘prime’ the indivudal for their session or competition.
    • It is fixated on exercises which will directly lead to performance improvements in following activities.
    • Developed using the principle of post-activation potentiation (PAP), this phase will now begin to transit into the workout/sport itself, meaning it will begin to incorporate sports-specific activities using rising intensities.
    • This phase serves two primary objectives:
      • Increasing intensity to a comparable level the athletes’ are about to compete in; and
      • Increasing improve subsequent performance utilising the effects of PAP.

After the completion of these three phases, and gradually increasing the intensity of the exercises as the warm-up progresses, individuals should be sufficiently prepared physically for the forthcoming session or competition.

Though there are no guidelines in this model in regards to the duration of each phase, this is something that should be tailored by the exercise professional based on the several factors such as (not an exhaustive list):

  • Time availability;
  • The individual’s physical requirements; and
  • Content of the main session.

2.7     Intensity and Duration of the Warm-up

It is difficult to recommend specific intensity and duration of warm-up for every person, but most research in this area suggests an increase in body and muscle temperature of approximately one to two degrees Fahrenheit to be adequate. A brisk 5-8 minute walk or a slow jog will generally produce sufficient warm-up to prepare the body for more strenuous exercise.

The duration and intensity of the warm-up should be adjusted according to the environmental temperature and the amount of clothing worn. The higher the environmental temperature and the greater the amount of clothing, the sooner the desired body temperature is attained.

It is also important to begin a major activity while still warmed-up. Ideally, the rest period should be no more than a few minutes. In any case, no more than fifteen minutes should elapse. When the beneficial effect of the warm-up has dissipated, the muscle temperature will have returned to pre-warm-up levels.

2.8     The Difference between Warming-up and Stretching: Warm-up then Stretch

There is an important difference between warming-up and stretching. Many people stretch and call it a warm-up – This is incorrect (Tousi, n.d; Walker, 2011b).

It is important to warm-up before stretching. If one stretches the muscles without prior warm-up, the muscles are cold and are more prone to injury, such as muscle tear or strain. Before exercising, begin with a warm-up period to raise the body temperature. The exerciser wants to get the heart pumping and increase blood flow to the muscles before stretching. Slow running in place, a slow aerobic dance, or a walk-jog is an ideal warm-up regimen to help prepare the muscles for stretching.

2.9     Warm-up Stretching

If utilised, the stretching phase of a warm-up should consist of two parts:

  • Static stretching (meaning they involve no motion); or
  • Dynamic stretching (meaning they involve motion).

It is important to note that:

  • Mobility and pulse-raising activities should precede any static stretching; and
  • Static stretches should be performed before any dynamic stretches. Dynamic stretching may result in overstretching, which damages the muscles, and performing static stretches first will help reduce this risk of injury.

2.10     Planning a Warm-up

Things to consider when planning a warm-up include:

  • The area (indoors/outdoors, size etc.);
  • The group (skill level, children versus adults etc.);
  • The type of lesson;
  • The type of warm-up;
  • Mobility (or joint rotation) exercises to be used;
  • Pulse-raising (or aerobic activity) exercises/games to be used;
  • Stretching exercises to be used.
  • Sport-specific activity for end of warm-up (e.g. practice basic skills and/or team games).
  • The equipment which may be required; and
  • Environmental factors.

2.11     During the Warm-up

Things to consider during the warm-up include:

  • The order of warm-up exercises (i.e. arms, trunk and legs);
  • The position of the instructor/trainer and exercisers; and
  • Timings.

2.12     Summary

In summary the benefits of warming-up include:

  • Performance may be improved;
  • Increased speed of contraction and relaxation of warmed muscles;
  • Dynamic exercises reduce muscle stiffness;
  • Greater economy of movement because of lowered viscous resistance within warmed muscles;
  • Facilitated oxygen utilisation by warmed muscles because haemoglobin releases oxygen more
  • readily at higher muscle temperatures;
  • Facilitated nerve transmission and muscle metabolism at higher temperatures; a specific warm up
  • can facilitate motor unit recruitment required in subsequent all out activity;
  • Increased blood flow through active tissues as local vascular beds dilate, increasing metabolism and muscle temperatures;
  • Allows the heart rate get to a workable rate for beginning exercise; and
  • Mentally focused on the training or competition.

PART THREE: THE COOL-DOWN

3.0     Introduction

“The cool-down should consist of a minimum of 5 to 10 minutes of low- to moderate-level activity.” (Bushman, 2017, p.94).

At the end of every exercise session it is important not to come to a sudden halt, the idea is to slow down gradually. Therefore, the purpose of the cool-down (also known as the warm-down) is to return the body to its pre-exercise state, just like a warm-up but in reverse. If you do stop suddenly, the heart continues to pump large amounts of blood to the body, but the absence of activity means this blood can pool in the limbs, making you feel faint or dizzy. Stopping too suddenly also slows the removal of waste products from the body, hampering the recovery process and increasing the likelihood of sore muscles (e.g. DOMS). All you need to do is spend 5-10 minutes at the end of the workout reducing the pace, allowing the heart rate and breathing to return to normal. Body temperature will remain elevated for a limited period, making the cool-down period the perfect time to perform some stretching.

Stretching during the cool-down section of the workout helps the muscles relax and return to their resting length. This is important because the muscles have a tendency to shorten if they are not stretched after the constant contractions involved in exercise and over time, this can restrict mobility.

However, it is worth noting that a brief workout stretch is not sufficient to improve flexibility, it will only assist in maintaining your current range of movement. Acknowledging this fact – that stretching (or flexibility) is just as much a component of overall fitness as strength or stamina – the British Army incorporates regular standalone flexibility sessions into its military physical training programmes on rest or recovery days.

3.1     The Purpose of the Cool-down

The purpose of the cool-down is to promote the removal of waste products accumulated in the muscles during the workout, maintaining a full range of motion in the applicable joints and muscles, and promote blood flow to damaged tissues.

During aerobic exercise the exerciser is working their heart within their target heart rate zone. The main purpose of cooling down is to bring the breathing rate, body temperature and heart rate back to normal slowly and under control. During the cool-down routine the exerciser is allowing the blood to properly redistribute itself to the heart. This redistribution helps rid the muscles of lactic acid which can build up around the muscles during an aerobic workout.

If the exerciser stops their aerobic exercise abruptly and does not cool down, the blood can pool up around the muscles in the legs. This can cause insufficient blood flow and oxygen to the brain giving a light headed and dizzy sensation. Dizziness, nausea and feeling worn out are common symptoms of an improper or no cool-down period. Research also suggests that a period of cooling down should be followed by a period of stretching (see below).

To this end the basic aims of cooling-down are to:

  • Eliminate waste (e.g. lactic acid) produced during exercise;
  • Encourage venous return;
  • Encourage the heart to slow down in a controlled manner;
  • Helps to gradually decrease body temperature;
  • Return muscles that have shortened due to use back to their original length.

“A proper cool-down is driven by both practical issues (e.g., avoiding fainting from a drop in blood pressure) and safety issues (e.g., avoiding negative changes in heart rhythm).” (Bushman, 2017, p.95).

3.2     Conduct of the Cool-down

The cool-down is similar to the warm-up, just in the reverse order.

  1. Sport-Specific Activity/Mobility:
    1. This should include sport-specific activity/general mobilising exercises to areas used during the main theme.
    2. Activity/exercises should be graduated to progressively lower the heart rate to ‘normal’.
  2. Dynamic stretching.
  3. Static stretching:
    1. The purpose is to return the muscles to their optimum length.
    2. Each stretch should be held for 15-30 seconds.

There is a general recommendation that the sport-specific activity/mobility part of the cool-down should be 10-20 minutes in duration but, as most exercisers may not have this time, 5 minutes should be considered the absolute minimum duration. Light dynamic stretches should be followed by static stretching, taking approximately 5-10 minutes (with 5 minutes as the minimum).

As an absolute minimum, the total time for a cool-down should be no less than 10 minutes.

Following this routine can help to reduce cramping, tightening, soreness in fatigued muscles, and perhaps even make you feel (psychologically) better.

3.3     Delayed Onset Muscle Soreness

DOMS or delayed onset muscle soreness is discussed in detail here, and whilst a cool-down immediately after a training session can aid in reducing the effects of DOMS, a light cool-down or even warm-up the next day can help alleviate the effects of lingering muscle tightness and soreness.

3.4     Summary

In summary the benefits of cooling-down include:

  • Aid in the dissipation of waste products, including lactic acid;
  • Reducing the potential for muscle soreness [LINK];
  • Reducing the chances of dizziness or fainting caused by the pooling of venous blood at the extremities;
  • Reducing the level of adrenaline in the blood; and
  • Allowing the heart rate to return to its resting rate.

PART FOUR: ROM, MOBILITY, FLEXIBILITY & STRETCHING

4.0     Introduction

This part of the article will discuss range of ROM (range of motion), mobility, flexibility and stretching in relation to the warm-up and cool-down routines.

4.1     Range of Motion (ROM)

This refers to the distance and direction a joint can move between the flexed position and the extended position. The act of attempting to increase this distance through therapeutic exercises (range of motion therapy – stretching from flexion to extension for physiological gain) is also sometimes called range of motion (Berryman-Reese and Bandy, 2010).

Joint ROM is an integral part of human movement. In order for an individual to move efficiently and with minimal effort, full ROM access across the joints is imperative (Berryman-Reese and Bandy, 2010). In addition, appropriate ROM allows the joints to adapt more easily to stresses imposed on the body and decreases the potential for injury.

Full ROM across a joint is dependent on two components (Berryman-Reese and Bandy, 2010):

  • Joint ROM; and
  • Muscle length.

Muscle length refers to the ability of a muscle crossing the joint to lengthen, allowing one joint or a series of joints to move through the available ROM (Berryman-Reese and Bandy, 2010). Improving ROM is achieved through mobility exercises which involve gradually increasing the ROM the joint will go through without pain, and specific stretching exercises to stretch all muscles or muscle groups.

4.2     Mobility

Flexibility, mobility and suppleness all mean the range of limb movement around joints.

In any movement there are two groups of muscles at work:

  • Protagonistic muscles which cause the movement to take place; and
  • Opposing the movement and determining the amount of flexibility are the antagonistic muscles.

4.3     Flexibility

Flexibility is the (absolute) range of movement in a joint or series of joints that is attainable in a momentary effort with the help of a partner or a piece of equipment. This means that flexibility is specific to a particular joint or set of joints rather than being something general to the body as a whole – being flexible in one particular area or joint does not necessarily imply being flexible in another.

Flexibility exercises have the potential to improve joint range of motion and physical function. Although fitness professionals may not be able to point to benefits such as a reduction in cardiovascular disease risk, stretching is recommended as part of a comprehensive training programme for adults.

4.4     Flexibility Variables

There are five variables to consider:

  • Frequency: Stretching activities should be included a minimum of 2 to 3 days each week for most adults although daily flexibility exercise is most effective.
  • Intensity: Describing the intensity of stretching to a client can be difficult as it is not a measurable entity like a treadmill speed. The fitness professional can use cues to help guide clients, such as moving within the range of motion to point of mild tightness without discomfort. A stretch should not create discomfort; if so, the client should release slightly. A stretch never should be painful.
  • Time (or Duration): At least 10 minutes is recommended per session in order to allow all the major muscle-tendon groups to be targeted with at least four repetitions of each stretch.
  • Type (or Mode): Flexibility can be improved using a wide variety of activities, including static stretching (active and passive), dynamic or slow movement stretching, and proprioceptive neuromuscular facilitation (PNF). Interestingly, when properly performed, even ballistic or ‘bouncing’ stretches can be as effective as static stretches for increasing joint ROM in individuals engaging in activities that involve ballistic movements such as tennis or basketball.
  • Volume: Each flexibility exercise per joint should be held at the point of tightness for 10 to 30 seconds. Time/duration and repetitions of the flexibility exercises should be adjusted to accumulate a total of 60 seconds of stretching at each joint. Recommendations for using PNF are to hold a 20% to 75% maximum voluntary contraction for 3 to 6 seconds, followed by 10 to 30 seconds of assisted stretch. Performing flexibility exercises at least 2 to 3 days per week is recommended with daily flexibility exercise being most effective.

4.5     Types of Flexibility

Typically, flexibility can be broadly classified as either:

  • Static (meaning they involve no motion); or
  • Dynamic (meaning they involve motion).

Currently, there are three recognised forms of stretching:

  • Dynamic Flexibility:
    • Also known as kinetic flexibility.
    • This is the ability to perform dynamic (or kinetic) movements of the muscles to bring a limb through its full range of motion in the joints.
  • Static-Active Flexibility:
    • Also known as active flexibility.
    • This is the ability to assume and maintain extended positions using only the tension of the agonists and synergists while the antagonists are being stretched.
    • For example, lifting the leg and keeping it high without any external support (other than from your own leg muscles).
  • Static-Passive Flexibility:
    • Also known as passive flexibility.
    • This is the ability to assume extended positions and then maintain them using only your weight, the support of your limbs, or some other apparatus (e.g. a chair or a barre).
    • Note that the ability to maintain the position does not come solely from your muscles, as it does with static-active flexibility.
    • Being able to perform the splits is an example of static-passive flexibility.

Research suggests that active flexibility is more closely related to the level of sports achievement than is passive flexibility. Active flexibility is harder to develop than passive flexibility (which is what most people think of as ‘flexibility’); not only does active flexibility require passive flexibility in order to assume an initial extended position, it also requires muscle strength to be able to hold and maintain that position.

4.6     Factors Limiting Flexibility

There are a number of factors that can limit flexibility, which can be classified as either internal or external influences (Gummerson, 1990; Hamill & Knutzen, 2009)):

  • Internal Influences:
    • Bone structure.
    • Muscle mass: Can be a factor when the muscle is so heavily developed that it interferes with the ability to take the adjacent joints through their complete range of motion (for example, large hamstrings limit the ability to fully bend the knees).
    • Excess adipose (fatty) tissue: Can impose a similar restriction as above.
    • Connective tissue:
      • Consisting of two types of fiber: collagenous connective tissue (provides tensile strength) and elastic connective tissue (provides elasticity).
      • Inactivity of certain muscles or joints can cause chemical changes in connective tissue which restrict flexibility.
    • The type of joint.
    • The internal resistance within a joint’s bony structure which can limit movement.
    • The elasticity of muscle tissue (e.g. muscle tissue that is scarred due to a previous injury is not very elastic).
    • The elasticity of tendons and ligaments (ligaments do not stretch much and tendons should not stretch at all).
    • The elasticity of skin (skin has some degree of elasticity, but not much).
    • The ability of a muscle to relax and contract to achieve the greatest range of movement.
    • The temperature of the joint and associated tissues (joints and muscles offer better flexibility at body temperatures that are 1 to 2 degrees higher than normal).
    • Any physical injury and/or disability.
  • External Influences:
    • The temperature of the place where one is training (a warmer temperature is more conducive to increased flexibility).
    • The time of day (most people are more flexible in the afternoon than in the morning, peaking from about 2:30pm-4pm).
    • The stage in the recovery process of a joint (or muscle) after injury (injured joints and muscles will usually offer a lesser degree of flexibility than healthy ones).
    • Age: Pre-adolescents are generally more flexible than adults, and younger adults more flexible than older adults.
    • Gender: Females are generally more flexible than males.
    • History of physical activity.
    • The individual’s ability to perform a particular exercise (i.e. practice makes better).
    • The individual’s commitment to achieving flexibility.
    • The restrictions of any clothing or equipment.

Another factor related to flexibility is water. Given that muscle is approximately 75% water, this seems sensible.

The majority of ‘flexibility work’ should involve performing exercises designed to reduce the internal resistance offered by soft connective tissues. Most stretching exercises attempt to accomplish this goal and can be performed by almost anyone, regardless of age or gender.

It should also be noted that increasing flexibility through stretching should be directed to the muscle fascia rather than the ligaments and tendons. Muscle and its fascia have more elastic tissue, with ligaments and tendons having less elastic tissue. Overstretching ligaments and tendons may weaken them, and the joints they are part of, meaning an excessive amount of flexibility may destabilise the joints and increase the individual’s risk of injury. Ligaments will tear when stretched more than 6% of their normal length and tendons are not even supposed to be able to lengthen!

4.7     Stretching

Stretching is a form of physical exercise in which a specific skeletal muscle (or muscle group) is deliberately elongated, often by abduction from the torso, in order to improve the muscle’s felt elasticity and reaffirm comfortable muscle tone (Hume and Kolt, 2004). The result is a feeling of increased muscle control, flexibility and range of motion. Stretching is also used therapeutically to alleviate cramps.

Research suggests there are many beneficial stretches that can improve ROM in athletes, especially runners (Yessis, 2006). However, another study found that classic ‘static stretching’ does not prevent injuries for runners (Aubrey, 2010).

Also, stretching does not prevent delayed onset muscle soreness (DOMS), either when performed before or after exercise, according to a Cochrane review in 2006 (Herbert and Noronha, 2007).

It is also suggested that one stretching exercise may not be enough to prevent all types of injury and, therefore, multiple stretching exercises should be used to gain the full effects of stretching (Yessis, 2006).

It has also been suggested that proprioceptive neuromuscular facilitation (PNF) stretching yields the greatest change in ROM, especially short-term benefits (Sharman et al., 2006). Reasoning behind the biomechanical benefit of PNF stretching points to muscular reflex relaxation found in the musculotendinous unit being stretched (the connection between a muscle and its tendon). However, it has been argued that the PNF benefits are due to influence on the joint where the stretch is felt.

4.8     Types of Stretch

Typically, stretches are broadly classified as either:

  • Static (meaning they involve no motion and affect dynamic flexibility); or
  • Dynamic (meaning they involve motion and affect static flexibility, and dynamic flexibility to some degree).

Currently, there are seven recognised forms of stretching:

  1. Ballistic stretching;
  2. Dynamic stretching;
  3. Active stretching;
  4. Passive stretching;
  5. Static stretching
  6. Iosmetric stretching;
  7. PNF stretching;

The following descriptions of stretches are intended as a guide only.

4.8.1     Ballistic Stretching

Ballistic stretching, related to dynamic stretching, uses the momentum of a moving body or a limb in an attempt to force it beyond its normal range of motion. All movements are completed explosively. For example, a rugby player executing a number of explosive drop style kicks on each leg which would utilise the hamstrings, knees and calves.

This is stretching, or ‘warming up’, by bouncing into (or out of) a stretched position, using the stretched muscles as a spring which pulls you out of the stretched position (e.g. bouncing down repeatedly to touch your toes.).

Some commentators suggest this type of stretching is not useful and can lead to injury, as it does not allow the muscles to adjust to, and relax in, the stretched position. Instead, it may cause them to tighten up by repeatedly activating the stretch reflex.

This type of stretching has been used by contact athletes such as MMA fighters, rugby players and footballers.

4.8.2     Dynamic Stretching

Dynamic stretching involves moving parts of your body and gradually increasing reach, speed of movement, or both. For example, a runner may conduct a series of drills involving ‘movement’ where the muscle groups are taken in and out of their ROM (Kovacs, 2009), such as walking lunges, burpees or froggie press-ups. Some of these routines have been used as circuits owing to the complex nature of the dynamics and movement.

Dynamic stretching should not be confused with ballistic stretching:

  • Dynamic stretching consists of controlled leg and arm swings that take you (gently!) to the limits of your range of motion.
  • Ballistic stretches involve trying to force a part of the body beyond its range of motion.

In dynamic stretches, there are no bounces or jerky movements. An example of dynamic stretching would be slow, controlled leg swings, arm swings, or torso twists.

Dynamic stretching improves dynamic flexibility and is quite useful as part of a warm-up for an active or aerobic workout (such as a dance or martial-arts class).

Dynamic stretching exercises should be performed in sets of 8-12 repetitions, although if after a few sets you feel tired then stop – tired muscles are less elastic which causes a decrease in the amplitude of your movements. After reaching the maximal range of motion in a joint in any direction of movement, you should not do many more repetitions of this movement in a given workout.

4.8.3     Active Stretching

Active stretching, also known as static-active stretching, is where the exerciser assumes a position and then holds it there with no assistance, other than using the strength of your agonist muscles, meaning the muscle is stretched through its ROM, owing to an opposing muscle group.

For example, bringing your leg up high and then holding it there without anything (other than your leg muscles themselves) to keep the leg in that extended position or stretching the hamstring muscle(s) by utilising the glutes and hip flexors to activate the stretch. The tension of the agonists in an active stretch helps to relax the muscles being stretched (the antagonists) by reciprocal inhibition.

Active stretching increases active flexibility and strengthens the agonistic muscles. Active stretches are usually quite difficult to hold and maintain for more than 10 seconds and rarely need to be held any longer than 15 seconds.

Many of the movements (or stretches) found in various forms of yoga are active stretches.

4.8.4     Passive Stretching

Passive stretching, also known as relaxed stretching and static-passive stretching, is where the exerciser assumes a position and holds it with some other part of their body, or with the assistance of a partner or some other apparatus.

For example, bringing your leg up high and then holding it there with your hand. The splits is an example of a passive stretch (in this case the floor is the ‘apparatus’ that you use to maintain your extended position).

Slow, relaxed stretching is useful in relieving spasms in muscles that are healing after an injury (However, individuals should check with their healthcare professional prior to stretching any injured muscles).

Relaxed stretching is also very good for ‘cooling down’ after training and may aid in reducing post-workout muscle fatigue, and soreness (aka DOMS).

4.8.5     Static Stretching

This is probably the oldest and most commonly used form of stretching in many sports. Static stretching is the most popular and widely known type of stretching (Stretching World, 2010). Implemented correctly in an exercise routine this type of stretching can vastly improve your limits of flexibility. Static Stretching as the name implies is static or ‘without movement’ and it involves stretching the target muscle for about 20-30 seconds for 1-3 repetitions (Stretching World, 2010).

For some, the terms passive stretching and static stretching are used interchangeably, for others there is a clear distinction.

  • Static stretching involves holding a position (i.e. you stretch to the farthest point and hold the stretch).
  • Passive stretching is a technique in which the exerciser is relaxed and makes no contribution to the range of motion. Instead, an external force is created by an outside agent, either manually or mechanically.

The reader should be aware of these alternative meanings when looking at other references/sources on stretching.

4.8.6     Isometric Stretching

Isometric stretching, a type of static stretching, involves the resistance of muscle groups through isometric contractions (or tensing) of the stretched muscles. The use of isometric stretching is one of the fastest ways to develop increased static-passive flexibility and is much more effective than either passive stretching or active stretching alone. Isometric stretches also help to develop strength in the tensed muscles (which helps to develop static-active flexibility), and appears to decrease the amount of pain/discomfort usually associated with stretching.

The most common ways to provide the needed resistance for an isometric stretch are to apply resistance manually to one’s own limbs, to have a partner apply the resistance, or to use an apparatus such as a wall (or the floor) to provide resistance. For example:

  • Manual Resistance: Holding onto the ball of your foot to keep it from flexing while you are using the muscles of your calf to try and straighten your instep so that the toes are pointed.
  • Partner Resistance: Have a partner hold your leg up high (and keep it there) while you attempt to force your leg back down to the ground.
  • Apparatus Resistance: ‘Push-the-wall’ calf-stretch where you are actively attempting to move the wall (even though you know you cannot).

Isometric stretching is not recommended for children and adolescents whose bones are still growing.

The correct method to perform an isometric stretch is:

  • Assume the position of a passive stretch for the desired muscle;
  • Then tense the stretched muscle for 7-15 seconds (resisting against some force that will not move, like the floor or a partner); and
  • Finally, relax the muscle for at least 20 seconds.

4.8.7     PNF Stretching

Proprioceptive neuromuscular facilitation stretching to give it its full name is a form of stretching used widely by physiotherapists and sports masseurs. Although it is a form of static stretching, the object of PNF stretching is to promote the muscles and joints to stretch the muscle tendon junctions in order to promote greater degrees of flexibility and ROM. This form of stretching can be further broken down into the following techniques:

  • Hold-Relax:
    • Also known as contract-relax.
    • After assuming an initial passive stretch, the muscle being stretched is isometrically contracted for 7-15 seconds, after which the muscle is briefly relaxed for 2-3 seconds, and then immediately subjected to a passive stretch which stretches the muscle even further than the initial passive stretch.
    • This final passive stretch is held for 10-15 seconds.
    • The muscle is then relaxed for 20 seconds before performing another PNF technique.
  • Hold-Relax-Contract:
    • Also known as contract-relax-contract or contract-relax-antagonsit-contract (CRAC).
    • This technique involves performing two isometric contractions: first of the agonists, then, of the antagonists.
    • The first part is similar to the hold-relax where, after assuming an initial passive stretch, the stretched muscle is isometrically contracted for 7-15 seconds.
    • Then the muscle is relaxed while its antagonist immediately performs an isometric contraction that is held for 7-15 seconds.
    • The muscles are then relaxed for 20 seconds before performing another PNF technique.
  • Hold-Relax-Swing:
    • This technique (and a similar technique called the hold-relax-bounce) actually involves the use of dynamic or ballistic stretches in conjunction with static and isometric stretches.
    • It is very risky, and is successfully used only by the most advanced of athletes and dancers that have managed to achieve a high level of control over their muscle stretch reflex.
    • It is similar to the hold-relax technique except that a dynamic or ballistic stretch is employed in place of the final passive stretch.

Like isometric stretching:

  • It is not recommended for children and people whose bones are still growing (for the same reasons; and
  • It helps strengthen the muscles that are contracted and therefore is good for increasing active flexibility as well as passive flexibility.

4.9     Elements of a Good Stretch

There are three factors to consider when determining the effectiveness of any particular stretch:

  • Isolation:
    • Ideally, a stretch should work only the muscles you are trying to stretch!
    • Isolating the muscles worked by a given stretch means that you do not have to worry about having to overcome the resistance offered by more than one group of muscles.
    • In general, the fewer muscles you try to stretch at once, the better.
    • For example, you are better off trying to stretch one hamstring at a time than both hamstrings at once.
    • By isolating the muscle you are stretching, you experience resistance from fewer muscle groups, which gives you greater control over the stretch and allows you to more easily change its intensity.
  • Leverage:
    • Having leverage during a stretch means having sufficient control over how intense the stretch becomes, and how fast.
    • If you have good leverage, not only are you better able to achieve the desired intensity of the stretch, but you do not need to apply as much force to your outstretched limb in order to effectively increase the intensity of the stretch.
    • This gives you greater control.
  • Risk:
    • Although a stretch may be very effective in terms of providing the athlete with ample leverage and isolation, the potential risk of injury from performing the stretch must be taken into consideration.
    • An exercise may offer great leverage and isolation but may subject joints to potentially injurious stresses. Think rotations that can strain ligaments or tendons, and pressure on vertebral discs that could lead to lower back problems.

There is a general consensus that passive stretches should be performed in sets of 2-5 repetitions with a 15-30 second rest in between each stretch.

4.10     Order of Stretching Exercises

The order of stretching exercises is not always a primary consideration when conducting stretching exercises, and there is limited research data.

For example:

  • When I attended my primary military fitness qualification (back in 1996) I was told to start with the upper body, the trunk (now core), and then legs (and repeat).
  • Some fitness professionals suggest starting from the head and working down, or from the feet and working up.
  • Some researchers have suggested designing flexibility training programmes that start with the core muscles of the stomach, sides, back and neck, and then work out to the extremities.
  • Others have recommended starting with sitting stretches, because there is less chance of accidental injury while sitting, before moving on to standing stretches.

Some would that the exact order in which individual stretches are done is not the main point of emphasis; the main priority is to cover all the major muscle groups and their opposing muscles, and to work on those areas that are most tight or more important for your specific sport.

Others would suggest that a formal stretching order is important because without it one can limit the amount of flexibility that can be developed in the smaller muscle groups. This is because movement in the smaller muscles is often limited by adjacent, larger muscle groups.

A consensus is starting to form that it is better to start the stretching sequence from the large muscles in the core area, then work up and down to the smaller muscle groups. In other words, start with the larger core muscles then move to the smaller ones, for example:

  • Back and torso;
  • Hips and pelvis;
  • Hamstrings;
  • Groin;
  • Quadriceps, calves, ankles, feet;
  • Shoulders, arms, wrists, hands; and
  • Neck.

However, there is another stretching sequence which suggests:

  • Stretching your back (upper and lower) first;
  • Stretching your sides after stretching your back;
  • Stretching your buttocks before stretching your groin or your hamstrings;
  • Stretching your calves before stretching your hamstrings;
  • Stretching your shins before stretching your quadriceps (if you do shin stretches); and
  • Stretching your arms before stretching your chest.

4.11     Six Essential Stretches

General consensus suggests there are six essential stretches:

  1. Quadriceps;
  2. Calf;
  3. Hip flexor;
  4. Lower back;
  5. Hamstrings; and
  6. The gluteals.

Realistically, this would represent an absolute minimum for time poor individuals. Exercisers should be aiming to stretch all the major muscle groups and joints.

PART FIVE: MISCELLANEOUS

5.0     Summary

Although there is a growing body of research relating to warming-up and cooling-down as part of a structured training programme, there is still varying opinion amongst fitness professionals on the exact composition and duration of a warm-up or cool-down – and the various components.

However, there is a general consensus that 8-10 minutes is the absolute minimum in order to provide a satisfactory safety net regarding physiological/psychological preparation and injury prevention.

A warm-up should gradually increase from resting to the level of the training or competition to be undertaken, whilst a cool-down should gradually decrease from the level of training or competition back to ‘normal’.

Although there is still ongoing debate over whether static stretching should be utilised in a warm-up, it has utility within the scope of a cool-down and even as a separate, and distinct, training session.

This article has provided the reader with a basic outline of warming-up and cooling-down, including the terms ROM, mobility, flexibility, and stretching, and how they correlate with these important routines.

5.1     Useful Publications

Bishop, D. (2003a) Warm Up I: Potential Mechanisms and the Effects of Passive Warm up on Exercise performance. Sports Medicine. 33(6), pp.439‐454.

Bishop, D. (2003b) Warm Up II: Performance Changes Following Active Warm Up and How to Structure the Warm Up. Sports Medicine. 33, pp.483‐498.

Fletcher, I. M. & Anness, R. (2007) The Acute Effects of Combined Static and Dynamic Stretch Protocols on Fifty‐meter Sprint Performance in Track‐and‐field Athletes. Journal of Strength & Conditioning Research. 21(3), pp.784‐787.

Shellock, F. G. & Prentice, W. E. (1985) Warming‐up and Stretching for Improved Physical Performance and Prevention of Sports Related Injuries. Sports Medicine. 2, pp.267‐278.

Shrier, I. (2004) Does Stretching Improve Performance? A Systematic and Critical Review of the Literature. Clinical Journal of Sport Medicine. 14(5), pp.267‐273.

Smith, C.A. (1994) The Warm Up Procedure: To Stretch or not to Stretch. A Brief Review. Journal of Orthopaedic and Sports Physical Therapy. 19, pp.12‐17.

Young, W. (2007) The Use of Static Stretching in Warm‐up for Training and Competition. International Journal of Sports Physiology & Performance. 2, pp.212‐216.

5.2     References

Anderson, B. & Anderson, J. (2010) Stretching. New York: Shelter Publications Inc.

Aubrey, A. (2010) For Runners, Static Stretching May Be Outdated. Available from World Wide Web: http://www.npr.org/templates/story/story.php?storyId=130509347. [Accessed: 30 March, 2011].

Avela, J., Kyrolainen, H. & Komi, P. (1999) Altered Reflex Sensitivity after Repeated and Prolonged Muscle Stretching. Journal of Applied Physiology. 86(4), pp.1283‐1291.

Berryman-Reese, N. & Bandy, W.D. (2010) Joint Range of Motion and Muscle Length Testing. 2nd ed. St Louis: Saunders-Elsevier.

Bushman, B. (ed) (2017) American College of Sports Medicine Complete Guide to Fitness and Health. 2nd Ed. Champaign, Illinois: Human Kinetics.

Bushman, B., Battista, R., Swan, P., Ransdell, L. & Thompson, W.R. (eds) (2014) ACSM’s Resources for the Personal Trainer. 4th Ed. London: Lippincott, Williams & Wilkins.

Gummerson, T. (1990) Mobility Training for the Martial Arts. London: A&C Black Publishers Ltd.

Hamill. J. & Knutzen, K.M. (2009) Biomechanical Basis of Human Movement. 3rd Ed. Philadelphia: Lippincott Williams & Wilkins.

Herbert, R.D. & de Noronha, M. (2007) Stretching to Prevent or Reduce Muscle Soreness after Exercise. Cochrane Database of Systematic Reviews 2007, Issue 4.

Hume, P.A. & Kolt, G.S. (2004) Stretching: Mechanisms and Benefits for Sports Performance and Injury Prevention. Physical Therapy Reviews. 9(4), pp189-206.

Knudson, D., Bennett, K., Corn, R., Leick, D. & Smith, C. (2001) Acute Effects of Stretching are not Evident in the Kinematics of the Vertical Jump. Journal of Strength & Conditioning Research. 15(1), pp.98‐101.

Kokkonen, J., Nelson, A. G. & Cornwell, A. (1998) Acute Muscle Stretching Inhibits Maximal Strength Performance. Research Quarterly Exercise and Sport. 4, pp.411‐415.

Kovacs, M. (2009) Dynamic Stretching: The Revolutionary New Warm-up Method to Improve Power, Performance and Range of Motion. New York: Ulysses Press.

Kurz, T. (2003) Stretching Scientifically: A Guide to Flexibility Training. 4th ed. London: Stadion Publishers.

Norris, M.C. (2007) The Complete Guide to Stretching. London: A & C Black Publishers Ltd.

Samll, K., McNaughton, L. & Matthews, M. (2008) A Systematic Review into the Efficacy of Static Stretching as Part of a Warm-Up for the Prevention of Exercise-Related Injury. Research in Sports Medicine. 16, pp.213-231. doi: 10.1080/15438620802310784.

Sharman, M.J., Cresswell, A.G. & Riek, S. (2006) Proprioceptive Neuromuscular Facilitation Stretching: Mechanisms and Clinical Implications. Sports Medicine. 36(1), pp.929-939.

Stretching World (2010) Static Stretching. Available from World Wide Web: http://www.stretchingworld.com/staticstretching.html. [Accessed: 03 April, 2011].

Tousi, (n.d.) The Importance of Warm-up and Stretching. Available from World Wide Web: http://www.entraineurdefoot.com/Tousienglish.html. [Accessed: 30 March, 2011].

Vetter, R.E. (2007) Effects of Six Warm-Up Protocols on Sprint and Jump Performance. Journal of Strength and Conditioning Research. 21(3), pp.819-823.

Walker, B. (2011a) The Anatomy of Stretching: Your Guide to Flexibility and Injury Rehabilitation. 2nd ed. London: Lotus Publishing.

Yessis, M. (2006). Runners Need Active Stretching. AMAA Journal. 18(2), pp.8–18.

Kaur, R., Kumar, R. & Sandhu, J.S. (2008) Effects of Various Warm Up Protocols on Endurance and Blood Lactate Concentration. Serbian Journal of Sports Sciences. 2(1-4), pp.101-109.