Muscle Oxygen Extraction is a Key Performance Adaptation in Sprint Canoe-Kayak

BACKGROUND: The aerobic contribution to sprint canoe-kayak performance ranges from ~37% to ~85% of total energy expenditure from shortest (200m) to longest (1000m) events. While systemic VO2max is a strong predictor of performance in 500m and 1000m races, the respective role of central and peripheral adaptations is poorly understood. PURPOSE: The purpose of this study was therefore to characterize the changes in oxygenation derived from portable near-infrared spectroscopy (NIRS) in various muscles during a VO2max test and two on-water time trials (TT: 200m and 500m or 1000m), and to examine the link between muscle oxygenation, cardiac output and performance. METHODS: Twenty one well-trained sprint canoe-kayak athletes (12 men: 8 kayakers (MK) and 4 canoeists (MC); 9 women: 4 kayakers (WK) and 5 canoeists (WC)) participated in three testing sessions: 1) an incremental VO2max test on a canoe or kayak ergometer; 2) a 200-m TT; and 3) a 500-m (WK and WC) or 1000-m (MK and MC) TT. NIRS monitors were placed on the latissimus dorsi (LD), biceps brachii (BB), and vastus lateralis (VL) during the 3 testing sessions to assess changes in muscle O2 saturation (SmO2, % from baseline). Cardiac output was measured by impedance during the VO2max test in a subset of 9 athletes. RESULTS: Performance in the 200m time trial correlated with both LD final SmO2 (R=0.700, p=0.01) and VL final SmO2 (R=0.568, p=0.02). Performance during the 500-1000m time trials correlated with BB final SmO2 obtained during the VO2max test (R=0.519, p=0.033) and with VO2max (L/min: R=-0.560, p=0.03). Maximal cardiac output was low (men: 26.2 ± 4.7L/min, women: 24.0 ± 2.6 L/min) and did not correlate with 200m (R=0.253) or 500-1000m (R=0.028) performance. CONCLUSION: These results confirm that systemic VO2max is related to performance in the longer canoe-kayak events, and suggest that peripheral adaptations (i.e., the muscle ability to extract oxygen during the effort) rather than central factors better contribute to success in this sport. The ability to extract oxygen during the effort appears to be a predictor of performance for both short and long events. These results indicate that training for sprint canoe-kayak athletes should emphasize the development of the peripheral component of oxygen consumption.