Purpose: Muscle oxygenation, expressed as muscle oxygen saturation (SmO2), is being increasingly measured in exercise. Whether different gait modes, or movement patterns, of the same load elicit differences in muscle oxygenation is not known. Thus, the aim of the present study was to compare the oxygenation of two leg muscles (vastus lateralis and gastrocnemius medialis), heart rate, respiratory gases, and blood lactate between two gait modes (walking and running) of the same speed and duration.
Methods: Ten men walked and run for 30 min each at 7 km/h in random, counterbalanced order. SmO2, heart rate, and respiratory gases were monitored continuously. Blood lactate was measured at rest, at the end of each exercise, and after 15 min of recovery. Statistical analysis was performed through repeated-measure ANOVA. Significance was declared if p < 0.05.
Results: Heart rate and oxygen consumption were higher in running compared to walking. Respiratory exchange ratio did not differ between gait modes. SmO2 was lower during exercise compared to rest and recovery, in gastrocnemius medialis compared to vastus lateralis, and in running compared to walking. Blood lactate increased during exercise but did not differ between gait modes.
Conclusion: Running caused higher deoxygenation in leg muscles (accompanied by higher whole-body oxygen uptake and heart rate) than walking at the same speed (one that was comfortable for both gait modes), thus pointing to a higher internal load despite equal external load. These findings may form the basis for similar comparisons in other healthy or diseased populations.