Prior Low- or High-Intensity Exercise Alters Pacing Strategy, Energy System Contribution and Performance during a 4-km Cycling Time Trial
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2014-10-20
Autores
Correia-Oliveira, Carlos Rafaell
Santos, Ralmony de Alcantara [UNIFESP]
Silva-Cavalcante, Marcos David
Bertuzzi, Romulo
Kiss, Maria Augusta Peduti Dal'Molin
Bishop, David John
Lima-Silva, Adriano Eduardo
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We analyzed the influence of prior exercise designed to reduce predominantly muscle glycogen in either type I or II fibers on pacing and performance during a 4-km cycling time trial (TT). After preliminary and familiarization trials, in a randomized, repeated-measures crossover design, ten amateur cyclists performed: 1) an exercise designed to reduce glycogen of type I muscle fibers, followed by a 4-km TT (EX-FIB I); 2) an exercise designed to reduce glycogen of type II muscle fibers, followed by a 4-km TT (EX-FIB II) and; 3) a 4-km TT, without the prior exercise (CONT). the muscle-glycogen-reducing exercise in both EX-FIB I and EX-FIB II was performed in the evening, similar to 12 h before the 4-km TT. Performance time was increased and power output (PO) was reduced in EX-FIB I (432.8 +/- 8.3 s and 204.9 +/- 10.9 W) and EX-FIB II (428.7 +/- 6.7 s and 207.5 +/- 9.1 W) compared to CONT (420.8 +/- 6.4 s and 218.4 +/- 9.3 W; P<0.01), without a difference between EX-FIB I and EX-FIB II (P>0.05). the PO was lower in EX-FIB I than in CONT at the beginning and middle of the trial (P<0.05). the mean aerobic contribution during EX-FIB I was also significantly lower than in CONT (P<0.05), but there was no difference between CONT and EX-FIB II or between EX-FIB I and EX-FIB II (P>0.05). the integrated electromyography was unchanged between conditions (P>0.05). Performance may have been impaired in EX-FIB I due a more conservative pacing at the beginning and middle, which was associated with a reduced aerobic contribution. in turn, the PO profile adopted in EX-FIB II was also reduced throughout the trial, but the impairment in performance may be attributed to a reduced glycolytic contribution (i.e. reduced lactate accumulation).
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Plos One. San Francisco: Public Library Science, v. 9, n. 10, 9 p., 2014.