A comparison of the neuromuscular, cardiopulmonary and muscle oxygenation responses to single‐ and double‐leg cycling in older adults

Abstract Previous work in younger adults has shown that during small muscle mass exercise, the tolerable degree of neuromuscular impairment at task failure is greater than during large muscle mass exercise. However, no study has compared the neuromuscular responses to small and large muscle mass exercise whilst matching exercise modality in older individuals. This study compared neuromuscular, cardiopulmonary and muscle oxygenation responses between incremental single‐ and double‐leg cycling (SLC and DLC). Eleven older adults (68 ± 4 years) completed incremental cycling with 3 min stages, with SLC work rate set at half of DLC. Between each stage, neuromuscular function of the right knee extensor was assessed using a customised recumbent cycle ergometer, with measurements including maximal voluntary contraction (MVC), voluntary activation (VA) and quadriceps potentiated twitch force ( Q tw, pot ). Oxygen consumption (), minute ventilation (), heart rate (HR), and near‐infrared spectroscopy (NIRS) and vastus lateralis electromyography (EMG) were measured throughout. Time to task failure did not differ between SLC and DLC ( P = 0.616). However, reductions in Q tw,pot were greater at task failure following SLC (45.7% ± 18.8%) than DLC (30.0% ± 14.0%; P = 0.049), with no differences in MVC ( P = 0.219) or VA ( P = 0.547). Electromyography measured during cycling was 22.5 ± 23.0% higher at task failure during SLC than DLC ( P = 0.001). Pulmonary , and HR were lower throughout SLC than DLC ( P ≤ 0.010), while oxygenated haemoglobin was 8.8 ± 8.0% higher throughout SLC than DLC ( P = 0.006). These results demonstrate that small muscle mass exercise permits a greater tolerable degree of contractile impairment to be incurred, with a reduced cardiopulmonary demand, relative to large muscle mass exercise in older adults.