Article

Comparison in muscle damage between maximal voluntary and electrically evoked isometric contractions of the elbow flexors.

School of Exercise, Biomedical and Health Sciences, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA 6027, Australia.
Arbeitsphysiologie (Impact Factor: 2.3). 05/2011; 112(2):429-38. DOI: 10.1007/s00421-011-1991-3
Source: PubMed

ABSTRACT This study compared between maximal voluntary (VOL) and electrically stimulated (ES) isometric contractions of the elbow flexors for changes in indirect markers of muscle damage to investigate whether ES would induce greater muscle damage than VOL. Twelve non-resistance-trained men (23-39 years) performed VOL with one arm and ES with the contralateral arm separated by 2 weeks in a randomised, counterbalanced order. Both VOL and ES (frequency 75 Hz, pulse duration 250 μs, maximally tolerated intensity) exercises consisted of 50 maximal isometric contractions (4-s on, 15-s off) of the elbow flexors at a long muscle length (160°). Changes in maximal voluntary isometric contraction torque (MVC), range of motion, muscle soreness, pressure pain threshold and serum creatine kinase (CK) activity were measured before, immediately after and 1, 24, 48, 72 and 96 h following exercise. The average peak torque over the 50 isometric contractions was greater (P < 0.05) for VOL (32.9 ± 9.8 N m) than ES (16.9 ± 6.3 N m). MVC decreased greater and recovered slower (P < 0.05) after ES (15% lower than baseline at 96 h) than VOL (full recovery). Serum CK activity increased (P < 0.05) only after ES, and the muscles became more sore and tender after ES than VOL (P < 0.05). These results showed that ES induced greater muscle damage than VOL despite the lower torque output during ES. It seems likely that higher mechanical stress imposed on the activated muscle fibres, due to the specificity of motor unit recruitment in ES, resulted in greater muscle damage.

Download full-text

Full-text

Available from: Guillaume Y Millet, Jul 05, 2015
0 Followers
 · 
105 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Electrical stimulation (ES) induces muscle damage that is characterised by histological alterations of muscle fibres and connective tissue, increases in circulating creatine kinase (CK) activity, decreases in muscle strength and development of delayed onset muscle soreness (DOMS). Muscle damage is induced not only by eccentric contractions with ES but also by isometric contractions evoked by ES. Muscle damage profile following 40 isometric contractions of the knee extensors is similar between pulsed current (75 Hz, 400 μs) and alternating current (2.5 kHz delivered at 75 Hz, 400 μs) ES for similar force output. When comparing maximal voluntary and ES-evoked (75 Hz, 200 μs) 50 isometric contractions of the elbow flexors, ES results in greater decreases in maximal voluntary contraction strength, increases in plasma CK activity and DOMS. It appears that the magnitude of muscle damage induced by ES-evoked isometric contractions is comparable to that induced by maximal voluntary eccentric contractions, although the volume of affected muscles in ES is not as large as that of eccentric exercise-induced muscle damage. It seems likely that the muscle damage in ES is associated with high mechanical stress on the activated muscle fibres due to the specificity of motor unit recruitment (i.e., non-selective, synchronous and spatially fixed manner). The magnitude of muscle damage induced by ES is significantly reduced when the second ES bout is performed 2-4 weeks later. It is possible to attenuate the magnitude of muscle damage by "pre-conditioning" muscles, so that muscle damage should not limit the use of ES in training and rehabilitation.
    Arbeitsphysiologie 08/2011; 111(10):2427-37. DOI:10.1007/s00421-011-2086-x · 2.30 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose was to study the effects on muscle function of an electrical stimulation bout applied unilaterally on thigh muscles in healthy male volunteers. One group (ES group, n = 10) received consecutively 100 isometric contractions of quadriceps and 100 isometric contractions of hamstrings (on-off ratio 6-6 s) induced by neuromuscular electrical stimulations (NMES). Changes in muscle torque, muscle soreness (0-10 VAS), muscle stiffness and serum creatine kinase (CK) activity were assessed before the NMES exercise (pre-ex) as well as 24h (d+1), 48h (d+2) and 120h (d+5) after the bout. A second group (control group, n = 10) were submitted to the same test battery than the ES group and with the same time-frame. The between-group comparison indicated a significant increase in VAS scores and in serum levels of CK only in the ES group. In the ES group, changes were more pronounced in hamstrings than in quadriceps and peaked at d+2 (quadriceps VAS scores = 2.20 ± 1.55 a.u. (0 at pre-ex); hamstrings VAS scores = 3.15 ± 2.14 a.u. (0 at pre-ex); hip flexion angle = 62 ± 5° (75 ± 6° at pre-ex); CK activity = 3021 ± 2693 IU·l(-1) (136 ± 50 IU·l(-1) at pre-ex)). The results of the present study suggested the occurrence of muscle damage that could have been induced by the peculiar muscle recruitment in NMES and the resulting overrated mechanical stress. The sensitivity to the damaging effects of NMES appeared higher in the hamstrings than in quadriceps muscles.
    Journal of sports science & medicine 01/2012; 11(4):592-9. · 0.90 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: PurposeThe aim of this study was to explore the efficiency of a preconditioning programme composed of neuromuscular electrical stimulation (NMES) in the protection against muscle damage induced by a subsequent bout of NMES.Methods Sixteen male volunteers were split up into a control group (CG; n = 8) and a preconditioned group (PCG; n = 8). Both groups attended two NMES bouts (test 1 and test 2) spaced 5 weeks apart. Each one consisted in 100 quadriceps contractions and 100 hamstrings contractions. PCG attended five additional progressive NMES sessions between test 1 and test 2. The outcome measures were the changes in muscle soreness [0–10 pain score on visual analogue pain scale (VAS)], muscle flexibility and serum creatine kinase (CK) activity; they were assessed before (pre-T1) and after (post-T1) test 1 and before (pre-T2) and after (post-T2) test 2.ResultsDamage markers increased similarly in both groups after test 1 (at post-T1, VAS scores = 4·18 ± 2 and 4·43 ± 1·56 cm in CG and PCG, respectively; CK activity = 2307 ± 3774 and 1671 ± 1790 IU l−1 in CG and PCG, respectively). Compared with test 1, these damage markers were reduced after test 2 in CG (at post-T2, VAS score = 2·68 ± 1·27 cm and CK activity = 218 ± 72 IU l−1). Muscle soreness was further reduced after test 2 in PCG (VAS score = 0·37 ± 0·74 cm).ConclusionsA protective effect against muscle damage can be obtained after only one NMES bout, and an additional protective effect can be induced by a preconditioning programme.
    Clinical Physiology and Functional Imaging 04/2014; 35(4). DOI:10.1111/cpf.12160 · 1.33 Impact Factor