Background: fatigue during voluntary muscular contractions is a complex and multifactorial phenomenon associated with both central changes and adaptations in the neuromuscular system.
The rate of force development has been considered an important parameter for measuring neuromuscular performance, however, there are lack of information about the fatigability according maximal
strength development in healthy subjects. The aim of this study was analyze the changes in maximal and submaximal peak torque according to maximal isometric force developed.
Methods: twenty healthy male subjects (≥ 18 years) physically independent were submitted to maximal voluntary isometric contraction (MVIC) at isokinetic dynamometer evaluation. Based
on MVIC values, the sample was distributed in three tertiles: high strength development (1º tertile), medium strength development (2º tertile) and little strength development (3º tertile). All
subjects were submitted to fatigue protocol (10 sets, 10 repetitions, speed of 70°s-1, 40” rest between sets at 70% of MVIC) involved extension (concentric action) of right knee. The following
parameters were evaluated before, during and after protocol: maximal peak torque (PTmax), maximal rate of isometric force development (RFDmax) and its slopes at isometric and dynamic condition
Results: significantly differences were found in maximal isometric peak torque around groups, however, the drop of 3º tertile (before: 374 ± 23, after: 216 ± 70) of force was higher
than 2º (before: 321 ± 11, after: 249 ± 48) and 1º (before: 257 ± 18, after: 175 ± 52). Percentual change of isometric peak torque of 3º tertile (-51 ± 7) was higher than 1º (-36 ± 14) and 2º (-21 ±
12) that differ between them. The isometric load of 3º tertile (262 ± 16) was highest than 2º (225 ± 8) and 1º (180 ± 12). Significantly differences was found in slope (Nm/repetition) of dynamic
parameters around groups (3º: -14 ± 0.7, 2º: -7 ± 0.5, 1º: -9 ± 0.5) and no differences were found between percentual change of concentric peak torque around groups (1º: -47.40 ± 7.57, 2º: -40.38 ±
5.35, 3º: -33.17 ± 4.00).
Conclusions: our data indicates that the higher and little strength development does not show higher endurance capacity of skeletal muscle during fatigue protocol in healthy man.