Monitoring the lactate threshold in world-ranked swimmers

Purpose: To determine whether lactate profiling could detect changes in dis crete aspects of endurance fitness in world-ranked swimmers during a season . Methods: Eight male and four female Australian National Team swimmers age d 20-27 yr undertook a 7 x 200-m incremental swimming step test on four occ asions over an 8-monlh period before the 1998 Commonwealth Games (CG): Janu ary (10 d before the World Championships), May (early-season camp), July (m idseason), and August (16 d before the CG). The lactate threshold (LT) was determined by a mathematical formula that calculated the threshold as a fun ction of the slope and y-intercept of the lactate-velocity curve. Results: Maximal 200-m test time declined initially from 127.7 +/- 4.2 s (January 19 98) to 130.2 +/- 4.5 s (May 1998) and 129.1 +/- 4.3 s (July 1998) before im proving to 126.8 +/- 4.2 s (August 1998) (P < 0.005). The swimming velocity at LT (s 100 m(-1)) also declined midseason before improving before the CG (P < 0.02) (January 1998: 70.5 +/- 2.1; May 1998: 72.0 +/- 2.2; July 1998: 72.2 +/- 2.2; and August 1998: 70.8 +/- 2.1). The blood lactate concentrat ion at the LT decreased (P ( 0.02) from 3.6 +/- 0.2 mM to 3.2 +/- 0.1 mM an d 2.9 +/- 0.2 mM before returning to 3.4 +/- 0.2 mM for January, May, July, and August, respectively. The lactate tolerance rating (LT5-10), defined a s the differential velocity between lactate concentrations of 5.0 and 10.0 mM, declined midway through the season (P < 0.015): 6.6 +/- 0.5 s.100 m(-1) , 7.7 +/- 0.5 s . 100 m(-1), 8.5 +/- 0.5 s . 100 m(-1), and 6.9 +/- 0.4 s . 100 m(-1), for January, May, July, and August, respectively. Despite these improvements in indicators of fitness, there was no significant improvemen t in competition performance across the season. Conclusions: Maximal effort 200-m time, lactate tolerance rating, and swimming velocity at LT (s . 100 m(-1)) all improved in world-ranked swimmers with training, but these chan ges were not directly associated with competition performance.