THE RELATIONSHIPS BETWEEN SPEED-STRENGTH ABILITIES OF LOWER EXTREMITIES OF YOUNG MILITARY PILOTS AND +Gz TOLERANCE

Abstract

INTRODUCTION: The level of muscle strength affects aircraft pilot's tolerance to physical stress caused by the frequent exposure to high +Gz forces. Whole body strength training, especially one that incorporates isometric exercises, can increase +Gz tolerance. Apart from high level of isometric strength, anaerobic power also seems to be an important component in tolerance to acceleration stress. Thus, the strength-training program should lead to an increase in anaerobic power as well, by improvement of the speed-strength abilities. The purpose of the study was to find the relationships between selected parameters of speed-strength abilities of lower extremities in young males and +Gz tolerance parameters. That relationship could then lead to development of a specific strength-training program for pilots. METHODS: Fifteen young males took part in the experiment. All of them were the first year cadets of the Polish Air Force Academy. The average values of basic parameters of physical characteristics of the subjects were: 74.7±8.4 kg body mass, 1.80±0.06 m body height and 20.5±0.9 years of age. In order to estimate the basic speed-strength parameters of lower extremities young pilots performed squats. The exercises were done on a computerized stand (locally made) under isokinetic (w = 0.2 rad/s) and isotonic (M = 20 Nm) conditions. The subjects performed three trials in order to estimate the maximal and average velocity (w), mechanical power (P) and moment of force (M) developed during the exercise. The pilots were exposed to excessive +Gz acceleration forces on the human centrifuge. Linear program with acceleration rate 0.1 G/s was used. Descriptive statistics for each parameter, as well as the Pearson's correlation matrix, were used. RESULTS: Group means (±SD) of three measured characteristics were as follows: for wmax 1.37 ± 0.12 rad/s, for Pmax 796 ± 119 W and for Mmax 3447 ± 465 Nm. Duration of centrifuge exposure was 68.3 ± 7.1 s (6.8 ± 0.7 G) with the maximum heart rates 162 ± 6 bpm. The strong relationships (r=0.81) were found between the relative value (to body mass) of average power (Pave/m) and average moment of force (Mave/m). The maximal and average moment of force (Mmax, Mave) developed by pilots were closely related to body mass (r=0.75 and r=0.68, respectively). We have not found any significant correlation between speedstrength parameters of lower extremities of young cadet-pilots and +Gz tolerance. CONCLUSION: The results suggest that there is no simple relationship between the power of legs' muscles and acceleration tolerance in young men. The protocol for further investigation should include exercises that involve large muscle groups and are not limited to the lower extremities only.