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The relationship between voluntary electromyogram, endurance time and intensity of effort in isometric handgrip exercise

  • W. West
  • A. Hicks
  • L. Clements
  • J. Dowling
Original Article

Abstract

The relationship between relative force, electromyogram (EMG) and time to fatigue was examined in seven male and seven female subjects [mean (SD) age, 21.7 (3.2) years] during isometric handgrip exercise. Subjects performed sustained submaximal contractions of the right handgrip at three different intensities: 30%, 50%, and 75% of the pretrial maximum voluntary contraction (MVC). EMG was sampled in 1-s epochs every 15 s during the contractions, and the integrated EMG (IEMG) values were then normalized to that of the pretrial MVC. As expected, time to fatigue was longest at 30% MVC and shortest at 75% MVC, but women performed consistently longer than men at each of the three intensities [woman vs men; 400.7 (35.8) vs 364.3 (34.4) s, 205.1 (15.6) vs 139.4 (13) s, and 89.9 (11.4) vs 66.4 (6.4) s, for 30%, 50%, and 75% MVC, respectively; P < 0.05)]. IEMG increased in a non-linear fashion over time during each trial, with the magnitude of IEMG being proportional to the intensity of the contraction. At the endurance limit, IEMG was greatest in the 75% MVC trial, however, no IEMG values reached those obtained in the related MVC [30%, 57.2 (6.9)%; 50%, 84.6 (5.7)%; 75%, 92.8 (7.4)%]. In conclusion, endurance time during sustained submaximal isometric handgrip exercise is dependent up on the intensity of the effort, with women having significantly larger endurance times than men. The related increase in IEMG is also proportional to the intensity of effort, however, the factors causing force to fail prior to the final IEMG reaching its predicted maximum remain to be elucidated.

Keywords

Fatigue Voluntary EMG Handgrip exercise 

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References

  1. Belanger AY, McComas AJ (1981) Extent of motor unit activation during effort. J Appl Physiol 51:1131–1135Google Scholar
  2. Bigland-Ritchie B, Furbush F, Woods JJ (1986) Fatigue of intermittent submaximal voluntary contractions: central and peripheral factors. J Appl Physiol 61:421–429Google Scholar
  3. Eason RG (1960) Electromyographic study of local and generalized muscular impairment. J Appl Physiol 15:479–482Google Scholar
  4. Fugelvand AJ, Zackowski KM, Huey KA, Enoka RM (1993) Impairment of neuromuscular propogation during human fatiguing contractions at submaximal forces. J Physiol (Lond) 460:549–572Google Scholar
  5. Gandevia SC (1992) Some central and peripheral factors affecting human motorneuronal output in neuromuscular fatigue. Sports Med 13:93–98Google Scholar
  6. Garland SJ (1991) Role of small diameter afferents in reflex inhibition during human muscle fatigue. J Physiol (Lond) 435: 547–558Google Scholar
  7. Garland SJ, McComas AJ (1990) Reflex inhibition of human soleus muscle during fatigue. J Physiol (Lond) 429:17–27Google Scholar
  8. Hannertz J, Grimby L (1979) The afferent influence on the voluntary firing range of individual motor units in man. Muscle Nerve 2:414–422Google Scholar
  9. Hayward L, Wesselmann U, Rymer WZ (1988) The effects of muscle fatigue on small diameter muscle afferents in the anesthetized cat (abstract). See Neurosci Abs 14:794Google Scholar
  10. Jones LA, Hunter IW (1983) Force and EMG correlates of constant effort contractions. Eur J Appl Physiol 51:75–84Google Scholar
  11. Lind AR, Petrofsky JS (1979) Amplitude of the surface electromyogram during fatiguing isometric contractions. Muscle Nerve 2:257–264Google Scholar
  12. Lippold OCJ, Redfearn JWT, Vuco J (1960) The electromyography of fatigue. Ergonomics 3:121–131Google Scholar
  13. Mathiowetz V, Weber K, Volland G, Kashman N (1984) Reliability and validity of grip and pinch strength evaluations. Br J Hand Surg 9A:222–226Google Scholar
  14. Maton B (1991) Central nervous changes in fatigue induced by local work. In: Atlin G, Beliveau L, Bouissou P (eds) Muscle fatigue: biochemical and physiological aspects. Masson, Paris, pp 207–221Google Scholar
  15. Maughan RJ, Harmon M, Leiper JB, Sale D, Delman A (1986) Endurance capacity of untrained males and females in isometric and dynamic muscular contractions. Eur J Appl Physiol 55:395–400Google Scholar
  16. Merton PA (1954) Voluntary strength and fatigue. J Physiol (Lond) 123:553–564Google Scholar
  17. Miller A, MacDougall JD, Tarnopolsky M, Sale D (1993) Gender differences in strength and muscle fibre characteristics. Eur J Appl Physiol 66:254–262Google Scholar
  18. Milner-Brown HS, Miller RG (1986) Muscle membrane excitation and impulse propagation velocity are reduced during muscle fatigue. Muscle Nerve 9:367–374Google Scholar
  19. Moritani T, Nagata A, Muro M (1982) Electromyographic manifestations of muscular fatigue. Med Sci Sport Exerc 14:198–202Google Scholar
  20. Niebuhr B, Marion R (1987) Detecting sincerity of effort when measuring grip strength. Am J Phys Med 66:16–24Google Scholar
  21. Petrofsky J, Phillips, CA (1985) Discharge characteristics of motor units and the surface EMG during fatiguing isometric contractions at submaximal tensions. Aviat Space Environ Med 56:581–586Google Scholar
  22. Petrofsky JS, LaDonne D, Rinehart J, Lind AR (1976) Isometric strength and endurance during the menstrual cycle. Eur J Appl Physiol 35:1–10Google Scholar
  23. Robinson M, Geisser M, Hanson C, O'Connor P (1993) Detecting submaximal efforts in grip strength testing with the coefficient of variation. J Occup Rehabil 45–50Google Scholar

Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • W. West
    • 1
  • A. Hicks
    • 1
  • L. Clements
    • 2
  • J. Dowling
    • 1
  1. 1.Department of KinesiologyMcMaster UniversityHamiltonCanada
  2. 2.School of Occupational/Physical TherapyMcMaster UniversityHamiltonCanada

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