EFFECT OF RECOVERY DURATION ON AEROBIC AND ANAEROBIC ENERGY YIELD DURING EXHAUSTIVE HIGH INTENSITY INTERMITTENT EXERCISE 396

To assess the effect of recovery duration on aerobic and anaerobic energy yield during exhaustive high intensity intermittent exercise, fourteen physical education students were tested on six separate days. An incremental exercise test (20W/min) was used to assess VO2peak and maximal workload(W max), and 5-6 submaximal workloads were used to obtain the VO2/work relationship (linear regression). They then performed four randomly assigned intermittent exercise test (IET). Each IET consisted of 3 cycling bouts with fixed recovery periods of 2.5, 5, 10 and 20 min (2R, 5R, 10R and 20R, respectively). All bouts were performed at an intensity 10% higher than Wmax(i.e., 116 ± 8% of VO2max). The anaerobic energy yield during each bout was computed as the maximal accumulated oxygen deficit (MAOD. Medbø et al. 1988), which decreased significantly between the 1st and 3rd bouts (2R=59 ± 17 to 25 ± 5, 5R=56 ± 15 to 31± 6, 10R=54 ± 15 to 38 ± 10, and 20R=53 ± 11 to 47± 10 ml eq O2/kg; all p<0.01). An exponential relationship was found between the percent decrease of MAOD across bouts and recovery time(t) in min: In(MAOD)=-0.0917·t+4.25 (r2=0.99, p<0.001). Time to fatigue was also reduced between the 1st and 3rd bouts: 144 ± 19 to 60 ± 11 s (2R, p<0.001), 138 ± 16 to 77 ± 10 s (5R, p<0.001), 139 ± 22 to 103 ± 14 s (10R, p<0.001) and 132± 15 to 128 ± 14 s (20R, p=0.1). Despite this decrease in time to fatigue, the contribution of the aerobic metabolism between the 1st and 3rd bouts, expressed as a percentage of the total energy yield, was unchanged for the 2R and the 5R IET, but increased for the 10R (61 ± 7 to 63 ± 7%, p<0.05) and the 20R IET (59 ± 6 to 63 ± 6, p<0.01). In conclusion, during exhaustive high intensity exercise, the anaerobic contribution to the energy yield decreased as an exponential function of the decrease in recovery period between bouts. Despite the marked decrease in time to fatigue in successive bouts, the relative contribution to energy yield by aerobic metabolism is maintained or increased.