Acute neuromuscular and endocrine responses and recovery to single session combined endurance and strength loadings: ‘Order effect’ in untrained young men.

Abstract

The purpose of this study was to investigate acute neuromuscular and endocrine responses and recovery to a single session of combined endurance and strength loading using two loading orders. Forty-two men were demographically matched to perform a single session of combined endurance+strength (E+S) or strength+endurance (S+E) loading. The strength loading was conducted on a leg press and included sets of power, maximal strength and hypertrophic loads with an overall duration of 30 minutes. The endurance loading was conducted on a bike ergometer and performed by continuous cycling over 30min at 65% of subject’s individual maximal Watts. Both loading conditions led to significant acute reductions in maximal force production (E+S, -27%, p<0.001; S+E, -22%, p<0.001), rapid force produced in 500ms (E+S, -26%, p<0.001; S+E, -18%, p<0.001) and counter movement jump jumping height (E+S, -15%, p<0.001; S+E, -12%, p<0.001) while no significant differences between the two loadings were observed. Maximal and explosive force production recovered after 48h following both loading conditions. Whereas no significant acute responses were found in concentrations of serum testosterone (T) and thyroid releasing hormone (TSH) in the two loading conditions, concentrations of T were significantly reduced in E+S during recovery at 24h (-13%, p<0.05) and 48h (-11%, p=0.068) but not in S+E and TSH following both loading conditions (24h, E+S, -32%, p<0.001; S+E, -25%, p<0.01; 48h, E+S, -25%, p<0.001, S+E,-18%, p<0.01). The present loading conditions showed that neuromuscular performance recovered already within 2 days, while endocrine function, observed particularly by decreased concentrations in serum testosterone following the E+S loading order, remained altered still after 48h of recovery. These results emphasize the different needs for recovery following two loading orders.