Handcycling with concurrent lower body low-frequency electromyostimulation increases acute oxygen uptake in elite wheelchair basketball players: An acute crossover trial

INTRODUCTION: Acute increases in oxygen uptake (VO2) during exercise are crucial for aerobic training adaptations and depend on the amount of muscle involved. VO2 capacity is limited during wheelchair handcycling due to restricted muscle involvement of the impaired lower body muscles. Handcycling with concurrent complementary low-frequency electromyostimulation (LF-EMS), applied to major lower limb muscles might lead to relevantly increased passive muscle involvement with higher oxygen uptake in elite wheelchair basketball (WCB) athletes.
METHODS: The squad of the German national WCB team (n=12, age: 25.6 ± 5.6 years, height: 1.75 ± 0.16 m, mass: 74.0 ± 21.7 kg, classification: 2.92 ± 1.26 a.u. (1.0 - 4.5 from least to most mobility)) completed 2×5 minutes of handcycling (60 rpm, ¾ bodyweight as resistance in watts) (HANDCYCLE) and handcycling with concurrent EMS of the lower extremities (EMS_HANDCYCLE). During EMS_HANDCYCLE, LF-EMS (impulse frequency: 4Hz, impulse width: 350μs, continuous stimulation) was applied to gluteal, quadriceps and calf muscles. The stimulation intensity (buttocks: 69.5 ± 22.3 mA, thighs: 66.8 ± 20.0 mA, calves: 68.9 ± 31.5 mA) was individually adjusted based on reported comfort tolerance for 5 minutes.
RESULTS: Large and significant mode-dependent differences in VO2 responses were found between HANDCYCLE and EMS_HANDCYCLE (17.60 ± 3.57 vs. 19.23 ± 4.37 ml⸱min-1⸱kg-1, p = 0.001, ηp2 = 0.69). Furthermore, ΔLactate was significantly lower in HANDCYCLE compared to EMS_HANDCYCLE (0.04 ± 0.28 vs. 0.31 ± 0.26 mmol⸱l-1, p = 0.036, ηp2 = 0.37). Although perceived effort did not differ between conditions (2.7 ± 0.9 vs. 2.9 ± 0.9 a.u., p = 0.293, ηp2 = 0.100), discomfort was rated lower during HANDCYCLE compared to EMS_HANDCYCLE (1.4 ± 1.3 vs. 3.9 ± 2.1 a.u., p = 0.002, ηp2 = 0.58).
CONCLUSION: Concurrent and complementary LF-EMS of the lower extremities during submaximal handcycling notably increases acute oxygen uptake and thus may serve as an additional cardiocirculatory training stimuli for improvements in aerobic capacity in wheelchair athletes. Future studies on tissue response and preservation when concurrently using LF-EMS in the long term are suggested.