Context:: Contrast baths (CB) is a thermal treatment modality used in sports medicine, athletic training, and rehabilitation settings. Proposed physiological effects of CB include increasing tissue blood flow and oxygenation and decreasing tissue swelling and edema to promote better healing, improved limb function, and quicker recovery.

Objective:: To investigate the physiological effects of CB on the intramuscular hemodynamics and oxygenation of the lower leg muscles using near-infrared spectroscopy (NIRS), an optical method for monitoring changes in tissue oxygenated (O₂Hb), deoxygenated (HHb), and total hemoglobin (tHb) as well as tissue oxygen saturation index (TSI%).

Design:: Descriptive laboratory study.

Patients or other participants:: Ten healthy men and women with a mean age of 29 (range = 17 ± 42) years, mean body mass index of 24.6 ± 3.2, and mean adipose tissue thickness of 6.4 ± 2.2 mm.

Intervention(s):: Conventional CB (10-minute baseline, 4 : 1-minute hot : cold ratio) was applied to the left lower leg.

Main outcome measure(s):: Changes in chromophore concentrations of O₂Hb, HHb, tHb, and TSI% of the gastrocnemius muscle were monitored during 10 minutes of baseline measurement, a 30-minute CB protocol, and 10 minutes of recovery using a spatially resolved NIRS.

Results:: After a 30-minute CB protocol, increases ( P < .05) in tissue O₂Hb (7.4 ± 4 μM), tHb (7.6 ± 6.1 μM), and TSI% (3.1% ± 2.3%) were observed as compared with baseline measures.

Conclusions:: Application of CB induced a transient change in the hemodynamics and oxygenation of the gastrocnemius muscle in healthy individuals. The effect of CB application in improving tissue hemodynamics and oxygenation may, therefore, support the therapeutic benefits of CB in the treatment of muscle injuries.