Rachel Sommerfeldt and Dr. A. Wayne Johnson, Department of Exercise
Neck pain and headaches related to neck pain will affect an estimated two thirds of the population at some time during their life. The pain may be caused by high-intensity exertion, such as whiplash, or from prolonged low-intensity exertion. An accepted explanation for neck pain is fatigue of the neck muscles caused by the sustained contraction which is required to hold the head in position. Studies suggest that a significant reduction of muscle function is a result of long term neck fatigue. Thus, an individual suffering from neck pain may have reduced muscle function, limiting activity and requiring changes in daily activity. Further, neck pain or fatigue may affect other areas of the body. One study found that leg muscle activation significantly decreased as the back muscles fatigued. Similarly, neck fatigue may limit upper extremity function, specifically hand dexterity and grip strength.
The forearm muscles are the primary muscles used in wrist motion and contribute to finger dexterity. Forearm fatigue is less common than neck fatigue but can occur from localized injury, repetitive hand or wrist use, deviated wrist posture, high forces, or other reasons. Severe forearm injuries may be immobilized to facilitate recovery, however, immobilizing causes a significant loss of muscle mass and can result in reduced control and range of use. Any injury to the forearm, including forearm muscle fatigue, can reduce hand dexterity, increase joint stiffness, and otherwise inhibit upper extremity dexterity.
This study analyzes the relationship between muscle fatigue and hand dexterity, specifically to determine if neck fatigue or forearm fatigue limits hand dexterity and/or grip strength. Due to the relation between forearm muscles and hand use, I hypothesized that forearm fatigue would reduce hand dexterity and/or grip strength. I also hypothesized that neck fatigue would reduce hand dexterity.
A Purdue pegboard (Figure 1) was used to evaluate hand and finger dexterity and a hand dynamometer (Figure 2) was used to measure grip strength. The Purdue pegboard is a hand dexterity assessment tool which measures the number of pegs placed in the pegboard during the timed test.
Tests were administered at each of four sessions which subjects attended. At an orientation and familiarization session (~30 minutes), subjects provided a baseline measurement and became familiar with the grip strength test as well as the pegboard test. During subsequent sessions, participants were measured without fatigue, with neck fatigue, or with forearm fatigue. During muscle fatigue sessions, the subject performed repeated isometric exercises to fatigue either neck extensor muscles or performed repeated flexion and extension to fatigue the forearm muscles. For the neck fatigue session, fatigue was determined by self-report and was confirmed by EMG. For the forearm fatigue session, fatigue was determined by a 25% decrease in work as calculated by the BioDex machine.
I conducted all testing and recorded data from each visit then used a computer analysis program to confirm that muscles were fatigued during the fatigue protocol. The number of pegs and the grip strength measurements were recorded and assessed for statistical significance. The number of pegs placed in the pegboard after forearm fatigue was significantly different than the number of pegs placed in the pegboard before forearm fatigue (2-sided T test value: .015). However the change in grip strength was not statistically significant (2-sided T test value: .429). These results suggest that forearm fatigue inhibits hand dexterity and grip strength, but that neck fatigue does not inhibit hand dexterity and grip strength.
Though these results did not show a significant relationship between neck fatigue and reduced hand dexterity, further research regarding the relationship between neck strength and upper extremity strength and dexterity may reveal a relationship. If additional research finds a relationship between muscle fatigue and hand dexterity, changes in clinical evaluation and treatment for individuals with impaired hand dexterity or grip strength may be necessary.
Overall this research has introduced me to the research process, equipment used to asses strength and skill, and some of the challenges associated with writing and executing research. I will use the skills that I have developed to help me critically analyze other research and possibly conduct additional research.
References
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