Eichelberger T1, Bilodeau M2
1Azusa Pacific University, Doctor of Physical Therapy, Azusa, United States, 2University of Ottawa, School of Rehabilitation Sciences, Ottawa, Canada
Background: Preferential use of the dominant (D) hand has been shown to be associated with an increased resistance to muscle fatigue compared with the non-dominant (ND) hand. Central fatigue (a decrease in the ability to maximally drive a muscle voluntarily or voluntary activation) has been reported to be greater in the ND first dorsal interosseous (FDI) muscle compared to the D FDI muscle of young adults. Many changes occur in the neuromuscular system with aging, which could influence the extent of differences between D and ND hand muscles. The force-generating capabilities of older adults, specifically, voluntary activation, has also been shown to be lower, compared to levels reported for young adults before, during, and after fatigue in various muscle groups. The discrepancy in central fatigue related to dominance has not yet been examined in older adults.
Purpose: The purpose of this study was to determine if differences in voluntary activation between the D and ND FDI muscle of young adults are present in the D and ND FDI muscle of older adults before, during, and after fatigue.
Methods: Twelve young (28.3±1.0) and eleven older (75.8±2.1) right-handed adults were tested. The main variable of interest was voluntary activation of the D and ND FDI before, during, and after a sustained maximum voluntary isometric index finger abduction contraction. Fatigue was induced by subjects sustaining a maximal voluntary isometric index finger abduction contraction until measured force dropped to 25% of the pre-fatigue maximum force. Subjects performed the fatigue task with the FDI of the D and ND hand in separate sessions.
The level of voluntary activation was determined by superimposing doublets of electrical stimulation upon the maximal contractions and quantifying any extra force produced as a percent of the doublet force at rest. Repeated-measures ANOVAs were used to assess fatigue-related changes in voluntary activation between D and ND FDI muscles and between age groups.
Results: Older adults exhibited no difference in central fatigue between the D and ND FDI in contrast to young adults, where the D FDI exhibited more resistance to central fatigue (p=0.04). Older adults had a significantly lower level of voluntary activation before fatigue (p 0.001), but had similar decreases in voluntary activation during fatigue in the respective FDI muscles when compared to young adults (p=0.69).
Conclusion(s): The lower level of voluntary activation in older adults before fatigue did not have an effect on the ability to activate the FDI muscle during fatigue. It appears that age-related changes at central levels can lessen differences in central fatigue between D and ND FDI muscles in old age.
Implications: Determining the role that voluntary activation and central fatigue play in the ability of older adults to generate and sustain force will improve our understanding of the neuromuscular adaptations that occur with aging, which ultimately affect the functional capacities of older adults. This understanding will assist with developing treatment protocols that may include biofeedback or electrical stimulation to maximize the force-producing capabilities of older adults.
Keywords: voluntary activation, aging, dominance
Funding acknowledgements: n/a
Purpose: The purpose of this study was to determine if differences in voluntary activation between the D and ND FDI muscle of young adults are present in the D and ND FDI muscle of older adults before, during, and after fatigue.
Methods: Twelve young (28.3±1.0) and eleven older (75.8±2.1) right-handed adults were tested. The main variable of interest was voluntary activation of the D and ND FDI before, during, and after a sustained maximum voluntary isometric index finger abduction contraction. Fatigue was induced by subjects sustaining a maximal voluntary isometric index finger abduction contraction until measured force dropped to 25% of the pre-fatigue maximum force. Subjects performed the fatigue task with the FDI of the D and ND hand in separate sessions.
The level of voluntary activation was determined by superimposing doublets of electrical stimulation upon the maximal contractions and quantifying any extra force produced as a percent of the doublet force at rest. Repeated-measures ANOVAs were used to assess fatigue-related changes in voluntary activation between D and ND FDI muscles and between age groups.
Results: Older adults exhibited no difference in central fatigue between the D and ND FDI in contrast to young adults, where the D FDI exhibited more resistance to central fatigue (p=0.04). Older adults had a significantly lower level of voluntary activation before fatigue (p 0.001), but had similar decreases in voluntary activation during fatigue in the respective FDI muscles when compared to young adults (p=0.69).
Conclusion(s): The lower level of voluntary activation in older adults before fatigue did not have an effect on the ability to activate the FDI muscle during fatigue. It appears that age-related changes at central levels can lessen differences in central fatigue between D and ND FDI muscles in old age.
Implications: Determining the role that voluntary activation and central fatigue play in the ability of older adults to generate and sustain force will improve our understanding of the neuromuscular adaptations that occur with aging, which ultimately affect the functional capacities of older adults. This understanding will assist with developing treatment protocols that may include biofeedback or electrical stimulation to maximize the force-producing capabilities of older adults.
Keywords: voluntary activation, aging, dominance
Funding acknowledgements: n/a
Topic: Older people
Ethics approval required: Yes
Institution: University of Iowa, USA
Ethics committee: Institutional Review Board
Ethics number: 2005
All authors, affiliations and abstracts have been published as submitted.
