October 20, 2019

Katie Kowalski, PhD Candidate, DPT

School of Kinesiology, Western University, London, Ontario, Canada.


  • Muscle fatigue is any activity-induced reduction in maximal strength or power and occurs not only in the muscle that is being exercised, but also in non-exercised muscles on the same or opposite side of the body. This is called non-local muscle fatigue.
  • Previously, it has been demonstrated that unilateral exercise of a muscle group leads to fatigue in the same muscle group on the opposite side of the body.
  • However, it is unknown if fatiguing exercise of a small muscle can elicit fatigue in a large muscle group on the opposite side.

How the study was done

  • Fifteen healthy males performed a fatiguing exercise task of their dominant first dorsal interosseus (FDI), a hand muscle that moves the index finger out to the side.
  • The fatiguing exercise task consisted of two 100-second maximum voluntary isometric contractions (MVICs) with 30 seconds of rest between sets.
  • At task completion, fatigue in the non-exercised FDI and elbow flexors on the opposite side of the body was assessed through declines in force during a single MVIC followed by 12 repeated MVICs using a work to rest ratio of 5:10 seconds.

What the researchers found

  • Fatiguing exercise of the dominant FDI led to significant declines in strength of the non-exercised FDI and elbow flexors on the opposite side of the body as demonstrated by MVIC force production decrements. These results suggest fatigue occurred in both a small and large muscle that were not involved in the exercise task.
  • Greater fatigue was reported for the non-exercised FDI than the elbow flexors.


  • Performing a unilateral fatiguing exercise in small muscles on one side of the body can lead to fatigue in non-exercised small and large muscle groups on the opposite side.
  • Therefore, individuals who are injured or recovering from surgery may benefit from using unilateral exercises to elicit non-local muscle fatigue to provide a training stimulus when local muscle contraction is too painful or contraindicated.

Take home message

  • Performing a unilateral fatiguing exercise of a small hand muscle leads to fatigue in non-exercised small and large muscles of the opposite arm.
  • This exercise method could be used to elicit a training or strengthening stimulus when an individual cannot perform strengthening exercises such as after some surgical procedures or immobilization in a cast or brace

Original Article:

The effect of dominant first dorsal interosseus fatigue on the force production of a contralateral homologous and heterologous muscle. Yimeng Li, Kevin E. Power, Paulo H. Marchetti, David G. Behm Appl Physiol Nutr Metab. 2019; 44(7): 704-712. doi: 10.1139/apnm-2018-0583″

This article is a summary of an article published in Applied Physiology, Nutrition & Metabolism. If you intend to cite any information in this article, please consult the original article and cite that source. This summary was written for the Canadian Society for Exercise Physiology and it has been reviewed by the CSEP Knowledge Translation Committee.