David H. Clarke

Strength Recovery from Static and Dynamic Muscular Fatigue

Abstract Thirty university students were each given two types of local fatiguing exercise utilizing a spring-loaded hand ergograph. Six minutes of dynamic contractions at the rate of 30 per minute caused strength to decline from an initial value of 45.7 kg. to a steady-state value of 27.6 kg. The half-time (rate of decline) was 89 sec. The corresponding figures for two minutes of continuous static exercise were 46.9 kg., 15.8 kg., and 38 sec. Mathematical analysis of these fatigue curves confirmed the results of others. The progress of recovery was observed for 10 minutes. A two-component exponential equation accounted for the observed progressive return of strength. However, the rate parameters were quite different in the two curves; recovery was much faster and followed a different pattern after static exercise.

Neuromotor Specificity and Increased Speed from Strength Development

Abstract Arm strength, effective arm mass, and speed in a lateral adductive arm movement were measured in 62 college men and remeasured ten weeks later. During this interval, half of the subjects were given weight training exercise that did not involve the movement, while the other half remained inactive in order to provide a control group. The average of the training group improved significantly in speed, strength, and strength/mass ratio, whereas the average of the control group declined. There was no correlation between individual differences in speed and strength/mass ratio, but individual changes in the ratio correlated significantly (r = .405) with individual changes in speed. Reaction time was not improved by weight training.

Correlation between the Strength/Mass Ratio and the Speed of an Arm Movement

Abstract The speed of a lateral arm movement and the strength/mass ratio were measured in 48 university male students. The correlation between the movement time and S/M was not significant (r = -.277) and verified results of similar studies from this laboratory. The reliability of individual differences for all variables was high. These findings support the concept that the ability to exert muscular strength in a coordinated manner is determined by a specific neuromuscular coordination pattern. There was no significant correlation found between reaction time and speed of movement.

Rate of muscle tension development and release under extreme temperatures.

Summary and ConclusionsThirty-one male subjects squeezed a hand dynamometer as rapidly and as forcefully as possible, the effort being recorded on fast-moving paper. At the count of three the hand was released explosively. Two such testing sessions were held; following the first measurement of tension development and release the subject immersed his arm in a water bath. On one occasion it was at a temperature of 10° C, on the other of 46° C.The subject then repeated the procedure with the hand ergograph. The force-time curves of the contraction were described mathematically by a three-component exponential equation. Very little difference existed in the rate parameters of the normal and hot conditions, but these parameters were markedly slowed by the application of cold. This was further reflected in the contributions that each component made to the total work integral. Similar results were obtained during the release phase; the rates were nearly identical for the normal and hot curves, but two or three times slower for the cold. The steady state force level, comparedwith the normal, was significantly increased under the hot condition and significantly depressed under the cold.

Energy Cost of Isometric Exercise

Abstract The metabolic cost of static exercise was studied in relation to work load. The exercise consisted of the subjects holding 50-, 35-, and 20-lb. weights with the knees partially flexed. Rather sizable oxygen requirements and oxygen debts were obtained, which seemed to increase linearly as the size of the weight increased. When compared with available data on dynamic work of equivalent metabolic cost, the results showed significantly smaller oxygen income and larger oxygen debt for the static exercise. These findings supported the theory that the local circulation was being occluded by the muscle tension during this type of exercise.

The correlation between strength and the rate of tension development of a static muscular contraction

Summary and ConclusionsTwenty-five young adult male subjects twice squeezed a hand ergograph as rapidly and with as much force as possible, each effort being recorded on fast-moving-paper. A succession of measurements were made along the force-time curves and the data individually fitted to a single component exponential equation. The correlation between maximal force and the time required to reach a criterion value (30 kg.) was high (r= −.85); the stronger the individual the more quickly he reached this goal. On the other hand, the correlation between maximum strength and the rate of change of the contraction was approximately zero (r=−.03), indicating that the pattern of development of muscular force is highly task specific. This supports the concept that such abilities are determined by separate neuromuscular coordination pathways of the central nervous system.

Social Status and Mental Health of Boys as Related to Their Maturity, Structural, and Strength Characteristics

Abstract The purpose of this study was to determine the relationship between criteria of personal and social adjustment and the maturity, structural, and strength characteristics of boys 9 through 14 years of age. The personal and social adjustment criteria were derived from a sociometric questionnaire and an inventory-type instrument, the Mental Health Analysis. The experimental variables consisted of skeletal age, various anthropometric tests, and selected strength test formulae and batteries. When the sociometric questionnaire was used, positive relationships between peer status and body size and muscular strength were found. However, when the inventory-type instrument was used, the results were conflicting and contrary to those with the sociometric questionnaire.

Relationship between Level of Aspiration and Selected Physical Factors of Boys Aged Nine Years

Abstract Utilizing a grip-strength test, 98 nine-year-old boys were asked to predict future performance on the basis of knowledge of past results on each of two succeeding endeavors with a hand dynamometer. Two aspiration discrepancy scores were computed and the subjects divided into three distinct groups: those with the highest positive scores, those with “zero” discrepancies, and those with the greatest negative scores. The differences between the means of these groups for various physical factors were tested for significance. Results indicated that boys who expressed higher levels of aspiration were physically superior in size and strength to those who expressed neither an increase nor a decrease in their assessments.

Objective Determination of Resistance Load for Ten Repetitions Maximum for Knee Flexion Exercise

Abstract The number of repetitions subjects could perform when resistive weight for knee flexion exercise was equal to 40, 45, 50, and 55 percent of the strength of the flexor muscles of the knee joint was determined. A resistance load of 55 percent was found satisfactory for obtaining the desired ten repetitions maximum. When compared with available data for knee extension exercise, it was found that while both repetition decrement curves appeared linear, more repetitions were performed for knee flexion exercise at the lighter loads. In addition, more variability and greater strength increases during the exercise program were obtained for knee flexion exercise.