Analyzing Forearm Circumference and Hand Dominance and Their Role in Forearm. Muscle Endurance. BIO-204L Human Physiology.

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1 Analyzing Forearm Circumference and Hand Dominance and Their Role in Forearm Muscle Endurance BIO-204L Human Physiology 6 November 2012 Shelby Morphew

2 Introduction: Today s society is predominantly right handed. Left hand dominant individuals are temporarily forced to use their non-dominant hands for daily activities (Incel et al. 2002). Daily preferential use has been shown to alter the physiological and mechanical properties of skeletal muscle (Alexander, De Luca & Erim, 1998). Depending on the use of a certain muscle, its qualities and responses will adapt. Physiological changes include the amount of time it takes for the motor unit to fire and induce a contraction. In motor units of the dominant hand, mean values for recruitment threshold, initial firing rate, and average firing rate were lower than those of the non-dominant hand (Alexander, De Luca & Erim, 1998). By having lower mean values for recruitment threshold, the likelihood of reaching more thresholds increases, which also increases the likelihood that the force of that contraction will be higher. These results lend credibility to the 10% rule. The 10% rule states that the dominant hand possesses a 10% greater grip strength than the nondominant hand (Peterson et al. 1989). This rule is more prevalent in right hand dominant individuals rather than those left hand dominant persons. Measurement of the muscle rather than hand function may provide a more reliable indication of differences between dominant and non-dominant hands (Armstrong 1999). Forearm circumference has provided the most practical method of assessing muscle mass and strength for both men and women (Anakwe, Huntley & McEachan, 2007). The object of this study was to determine if there was any correlation between forearm circumference, hand dominance, and muscular endurance. The research question was as follows: is there a significant difference between the average number of repetitions per second and hand dominance? The hypothesis was that the dominant hand

3 average repetitions per second would be higher than the average repetitions per second on the non-dominant hand. Materials/Methods: For this experiment, eighteen subjects were measured for forearm circumference, asked about hand dominance, and performed one trial of repetitions of wrist curls using a five-pound weight until fatigue was felt. Each subject s left and right forearm were measured at what was considered the midpoint. The entire forearm, from wrist to the bend at the elbow, was measured using a meter stick and after dividing that number by two, a string was wrapped around that point. The string was then measured against the meter stick and that is how forearm circumference was determined. Along with this, hand dominance of each subject was attained and noted. The subject was asked to place the forearm against a plastic rectangular box with the palm up. A five-pound weight was placed in the palm and wrist curls were started. The subject was asked to count the repetitions they performed while the experimenter used a stopwatch to time from when the subject started until when the subject stopped. The experimenter reserved the right to end the subject s test if fatigue was observed; signs of fatigue included struggle to lift the weight, if the forearm rose off the box, if the subject couldn t continue, or if the subject complained of a muscle cramp. All information was kept in a table. Results: All data was recorded in (Table 1). The paired t-test value and correlation coefficient was recorded in (Table 2). Dominant hand repetitions per second vs. nondominant hand repetitions per second are compared in (Figure 1).

4 SUBJECT Table 1. All data recorded during experimental trials. LEFT CIRCUM. RIGHT CIRCUM. L. REPS R. REPS L. TIME R. TIME REPS/SEC NON- REPS/SEC 1 24 cm 24 cm R :27 1: cm 20.5 cm R :01 2: cm 20 cm R :55 1: cm 22 cm R :53 1: cm 20.5 cm R :04 1: cm 20 cm R :55 1: cm 24.5 cm R :41 0: cm 21.5 cm R :37 1: cm 18.5 cm R :09 2: cm 27.5 cm R :13 1: cm 24 cm R :12 1: cm 24 cm L :55 0: cm 25.5 cm R :51 1: cm 25 cm R :18 1: cm 22 cm R :34 1: cm 23 cm R :06 1: cm 23 cm R :06 1: cm 22 cm R :16 1: Figure 1. Dominant hand repetitions per second compared to the repetitions per second of the non-dominant hand. 2.5 Average Reps per Second REPS/SEC NON- REPS/SEC Number of Participant

5 Table 2. Statistical tests calculated Paired T-Test Value Correlation Coefficient Converted Correlation Coefficient Discussion: The hypothesis for this experiment was that the dominant hand would be able to perform more repetitions per second than the non-dominant hand. A majority of the participants performed more repetitions per second with the dominant hand than what they performed with the non-dominant hand. Most participants were able to perform more repetitions on average with their dominant hand, however not every participant was able to do so. The p-value was greater than.05; therefore, there was no significant difference between the repetitions performed by the dominant and non-dominant hands. It has been determined that there is no real relationship between forearm circumference and muscular strength. The forearm circumference varied between each subject and between each dominant arm. Literature Cited: Alexander, A., De Luca, C., & Erim, Z Hand dominance and motor unit firing behavior. Journal (Journal of Neurophysiology), 80(3); Anakwe, R., Huntley, J., & McEachan, J. (2007). Grip strength and forearm circumference in a healthy population. Journal of Hand Surgery, 32(2), Armstrong, C., & Oldham, J A comparison of dominant and non-dominant hand strengths. Journal (Journal of Hand Surgery), 24(4); Incel, N., Ceceli, E., Durukan, P., Erdem, H., & Yorgancioglu, Z Grip strength: Effect of hand dominance. Journal (Singapore Medical Journal), 43(5); Peterson, P., Petrick, M., Connor, H., & Conklin, D Grip strength and hand dominance: Challenging the 10% rule. Journal (American Journal of Occupational Therapy), 43(7);

Elbow Exercise Program

Elbow Exercise Program Name: Date: Diagnosis: Date of Surgery: 1. Deep Friction Massage deep transverse friction across area of elbow that is sore. 5 minutes, several times daily. 2. Grip grip apparatus,