Heart rate and oxygen saturation of vastus lateralis and gastrocnemius medialis muscles at maximal exercise intensity: a comparison between treadmill, elliptical trainer and cycle ergometry

Abstract

Maximal exercise intensity is widely used to assess physiological responses in various populations. The determination of muscle oxygen saturation (SmO₂), using the emerging easy-to-use technique of near-infrared spectroscopy (NIRS), combined with the heart rate (HR) in response to different exercise modes (or ergometers), remains unclear. The aim was to compare the changes in SmO₂ in the gastrocnemius medialis (GM) and vastus lateralis (VL) muscles, as well as the HR response at maximal exercise intensity performed on a treadmill, an elliptical trainer and a cycle ergometer.

Fourteen healthy volunteers (age = 34.9 ± 9.1 years; height = 169.4 ± 8.6 cm; weight = 69.7 ± 9.8 kg) performed three incremental tests to maximal intensity on a treadmill, an elliptical trainer, and a cycle ergometer on different days (interspersed by at least 72 hours) in a random order. During the incremental tests, the HR (Garmin HRM3-SS, Kansas, USA) and the SmO₂ (Moxy 3, Fortiori Design LLC, Hutchinson, USA) of VL and GM muscles were collected. The data of the last intensity level with one minute duration was used to determine average HR (HR_avg), peak HR (HR_peak), average SmO₂ (SmO_2avg) and minimum SmO₂ (SmO_2min) in VL and GM muscles.

Repeated measures ANOVA revealed an exercise mode effect on HR_avg (F_2,26=12.44, p=0.001, η²=0.150) and HR_peak (F_2,26=13.15, p=0.001, η²=0.170). Higher values were found on HR_avg on treadmill vs. cycle (177.2±7.5 vs. 167.5±13.4 bpm, p=0.005) and on elliptical (175.0±9.3 bpm, p=0.018) vs. cycle. A similar pattern was found on HR_peak with higher values on treadmill vs. cycle (183.9±2.1 vs. 172.9±3.7 bpm, p=0.004) and elliptical (180.5±2.5 bpm, p=0.017) vs. cycle. An exercise mode effect of SmO_2min in VL (F_2,20=5.24, p=0.015, η²=0.230) showed lower values on elliptical vs. cycle (15.0±10.7 vs. 37.6±18.2%, p=0.035). An exercise mode effect was also found in GM on SmO_2avg (F_2,24=27.19, p<0.001, η²=0.530) and SmO_2min (F_2,24=18.35, p<0.001, η²=0.450). Lower values were found on GM SmO_2avg on treadmill vs. cycle (27.3±9.4 vs. 57.6±14.9%, p<0.001) and elliptical (33.0±12.1%, p<0.001) vs. cycle. Similarly, the SmO_2min was lower on treadmill vs. cycle (21.8±9.0 vs. 48.3±15.2%, p<0.001) and elliptical (25.3±13.2%, p=0.002) vs. cycle.

The treadmill and the elliptical trainer promoted higher HR responses at maximal intensity, probably justified by the amount of active muscle mass and for being body-weight support exercises. The SmO₂, as a local variable, shows that the technique and body position in the elliptical trainer requires more the VL, and the treadmill requests more the GM. This exercise mode expertise is crucial for exercise prescription.