MAXIMAL LACTATE STEADY STATE & SUBMAXIMAL LACTATE THRESHOLD CYCLING SPEEDS WHEN GLYCOGEN DEPLETED.

Abstract

1861 This study examined the influence of glycogen depletion upon cycling speed at maximal lactate steady state (MLSS) and at the lactate inflection point, as determined by a submaximal anaerobic threshold test (SMAT). Eight male competitive recreational mountain bikers were recruited. Initially, peak aerobic power was established from a 2k time trial performed on a computerized cycle roller system with each subject using their own bicycle and connected to a SensorMedics Horizon II MMC for gas exchange data. CS established (via linear regression analysis of speed versus the inverse of time) from the 2k time trial result, together with further trials over 6k and 10k, was used as the basis for the MLSS and SMAT protocols. These protocols were conducted three times over a 14 day period under the following circumstances; normal mixed diet conditions (ND), after extensive exhaustive exercise designed to deplete glycogen stores (GD), and after a return to a normal diet (RND). The MLSS protocol required a 2k time trial, followed by 6 incremental speed stages performed on the computerized roller system each lasting 3 minutes from 84%CS to 104%CS. Blood lactate (B[La-]) measures were taken after each stage and, in combination with cycling speed, were used to determine MLSS speed for each individual. The SMAT consisted of an incremental test of 6 x 3 minutes using the same%CS levels as the MLSS protocol. Again, B[La-] measures were taken immediately after each stage. No difference between the speeds at MLSS and SMAT across all three experimental conditions were observed(p>0.05). However, B[La-] values at MLSS and SMAT in the GD condition were significantly lower than in the ND and RND circumstances(p<0.05). In addition, the peak B[La-] values after the 2k time trials prior to each MLSS protocol were also lower in the GD condition. Peak aerobic power levels were unaltered between conditions (p>0.05), although a trend towards slower performance times for the 2k in the GD state was seen. These results clearly suggest that the reliance upon fixed B[La-] levels as decisive monitoring parameters is suspect unless rigid and probably invasive control measures are ensured.