EFFECTS OF PRIOR EXERCISE ABOVE CRITICAL POWER ON MUSCLE FATIGUE

Na postagem do blog esse mês vou demonstrar um trabalho feito pelo nosso grupo de pesquisa (LAEF/CNPq - CDS/UFSC) que foi apresentado no último congresso internacional do Colégio Europeu de Ciências do Esporte - European College of Sport Science.

Helal, LCAS.¹, Souza, KM.¹, de Lucas, RD.¹, Nascimento, PC.¹, Guglielmo, LGA.¹, Denadai, BS.²

¹UFSC (Florianópolis, Santa Catarina, Brazil), ²UNESP (Rio Claro, São Paulo, Brazil)

Introduction

The physiological nature of anaerobic work capacity (AWC) has received little consideration in comparison to critical power (CP). Therefore, the aim of this study was to analyze the influence of prior exercise performed at different work rates above CP (with the same AWC rate depletion) on muscle fatigue during a subsequent isokinetic cycling sprint.

Methods

Fifteen healthy male subjects (mean ± SD; age, 26.0 ± 3.5 years; weight, 76.6 ± 10.4 kg; height, 178.2 ± 7.6 cm) volunteered to participate in this study. Each subject performed the following testing stages: 1) a ramp incremental test (25 W/min) to measure maximal oxygen uptake (VO_2max) and maximal power output (P_max); 2) a 5-s all-out isokinetic sprint test at 120-rpm to measure cycling peak torque in control condition (T_CON); 3) four constant work rate tests performed to exhaustion (over a range of times between 2 and 12 min) for CP and AWC determination; and 4) two constant work rate tests, each at work rate set to deplete 70% AWC (the time integral of the work rate above CP consuming 70% of AWC) either 3-min or 10-min, followed immediately by a 5-s all-out isokinetic sprint test at 120-rpm to measure cycling peak torque in the experimental conditions (T_EXP3min and T_EXP10min). Peak torque was considered as the average of the peak torque for each leg in all conditions. For comparisons, one-way repeated measure ANOVA followed by Bonferroni’s paired t-test was used. The level of significance was set at p < 0.05.

Figure 1. Schematic illustration of the experimental tests. A) 5 s all-out isokinetic exercise performed immediately after the fatiguing exercise set to deplete 70% W’ in 3 min. B) 5 s all-out isokinetic exercise performed immediately after the fatiguing exercise set to deplete 70% W’ in 10 min.

Results

The VO_2max and P_max were 3.71 ± 0.49 L.min^-1 and 322 ± 26 W, respectively. The CP and AWC were 207 ± 17 W (r² = 0.99 ± 0.01; SEE = 3.9 ± 2.7 W; 64.3 ± 2.7% P_max) and 21.3 ± 4.2 kJ, respectively. The constant work rate tests, which were set to deplete 70% AWC (14.9 ± 3.0 kJ) in 3 min and 10 min, were performed at 289 ± 25 W (89.8 ± 2.9% P_max) and 231 ± 19 W (71.9 ± 2.2% P_max), respectively. T_EXP3min (108.4 ± 19.8 Nm) and T_EXP10min (112.1 ± 23.0 Nm) decreased significantly (F = 19,68; p < 0,001) in the same magnitude (p  = 0,46) in comparison to T_CON (135.5 ± 20.2 Nm).

Discussion

The result of the present study is consistent with the idea that AWC is depleted at a rate that bears some proportionality to the magnitude of the work rate requirement above CP (Fukuba et al., 2003; Jones et al., 2010). We conclude that prior exercise above CP produces a similar level of muscle fatigue independent of the work rate performed when AWC is depleted at the same rate.

References

Fukuba Y, Miura A, Endo M, Kan A, Yanagawa K, Whipp BJ (2003). Med Sci Sports Exerc, 35 (8), 1413-1418.

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