Muscle Damage And Isometric Peak Torque Following Two Eccentric Training Protocols With Different Muscle Length In Healthy Males

Introduction
It has been shown that eccentric loading is beneficial for increasing muscle size and strength [2]. However, this exercise
has been shown to cause muscle damage and perturbations in muscular performance [5]. Furthermore, these changes in
muscle seem to depend on muscle length during the eccentric exercise [4]. The purpose of the present study was to
investigate the effects of short muscle length (SML) and long muscle length (LML) during eccentric exercise on muscle
damage and performance indicators.

Methods
Using an isokinetic dynamometer at 1.05 rad/s, 12 healthy male volunteers (21.0 ± 1.0 years) randomly underwent two
exercise sessions, one on each leg, 14 days apart. During each session, subjects had to accomplish 12 sets of 10
maximal voluntary efforts in seated and prone positions to achieve quadriceps SML and LML, respectively. Muscle
damage [delayed onset muscle soreness (DOMS) and range of motion (ROM)] and muscle performance [isometric peak
torque at 60o (IPT60
o) and 110o (IPT110
o) knee flexion] indicators were assessed pre-exercise and 24, 48, 72 as well as 96
h post-exercise.

Results
Compared to baseline, DOMS and ROM changed significantly at all time points after both exercise sessions. DOMS
and ROM also revealed greater changes after SML compared to LML exercise at almost all time points of assessment
(Table 1). IPT60
o and IPT110
o changed significantly only after SML exercise until 24 and 48 hours respectively. SML
exercise caused significant changes compared to LML exercise at 48 hours in IPT60
o and at 48 and 72 hours in IPT110o(Table 1).

Discussion
In conclusion, both SML and LML quadriceps eccentric exercise caused muscle damage but SML affected muscle to a
greater degree. Muscle performance perturbations were more evident after SML compared to LML. These results could
be attributed to damage of the elastic components of muscle, which add to the tension present in the muscle when it is
stretched [1]. Additionally, the higher neural activation observed for the knee extensor muscles at 90o compared to 180o
hip angle [3] may have further contributed to the current findings.

References
[1]. Crawford CNC. and James NT. (1980). The design of muscles. London: William Heinemann
[2]. Hortobagyi T. et al. (1998). J Appl Physiol, 84: 492-498
[3]. Maffiuletti NA. and Lepers R. (2003). Med Sci Sports Exerc, 35: 1511-1516
[4]. Newham DJ. et al. (1988). Clinical Science, 74: 553-557
[5]. Paddon-Jones D. and Abernethy PJ. (2001). Med Sci Sports Exerc, 33: 1213-9.

NOTA: O texto com a iconografia está no anexo.

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