INTRODUCTION

The purpose of this study was to determine whether isotonic back squats or isotonic power cleans were a better predictor of max. anaerobic power, as measured by vertical jump performance and vertical force measurements, and if differences existed between gender.

REVIEW AND THEORY

An athlete's ability to produce high amounts of power forcefully and quickly correlates highly with success in sport (Poidomoni, 1991). Anaerobic power is defined as the exertion of force through a given distance in as short a time as possible (Beckenholdt & Mayhew, 1983). Anaerobic power has become a key ingredient in successfully competing in sport (Kraemer & Fleck, 1987), so there is a need to find ways to improve anaerobic power safely and efficiently.

Two popular modes for increasing lower body strength and power are the isotonic parallel squat and the isotonic power clean (Chandler & Stone, 1991; Enoka, 1979). Although these training modes are of vital importance to trainers and coaches, both of these techniques have notable risks of injury even when being performed properly. It would be advantageous to find the best predictor of maximum anaerobic power (MAP), thereby limiting the injury problems many athletes face today.

The purpose of this research was to investigate slow isotonic back squat performance compared to fast isotonic power clean performance as predictors of the max. anaerobic power of 18-21 year-old female and male athletes.

PROCEDURES

The subjects in this research consisted of a convenience group of 18-21 year-old male and female Division One college athletes. All athletes were involved with varsity sports (gymnastics, track, volleyball, basketball, and football) but not in-season at the time of testing. All had been training for at least ten weeks with a collegiate strength staff on back squat and power clean lifts and had no previous injuries detrimental to performance on the lifts. Participants all signed informed consent forms.

Independent variables included the lift being performed (i.e., back squats or power cleans) and gender. The max. on each lift was determined using a three-repetition protocol. Proper form was used on all lifts (e.g., parallel back squats and the full catch on the power clean).

Participants performed 10 vertical counter-movement jumps, with height of jump, peak vertical force, and the time-to-peak vertical force, as measured via a force plate (Bertec force plate, Model 4060A) calibrated to standard specifications, being the variables recorded. Data were collected and filtered at a rate of 500 Hz. Multiple regressions were calculated between the subjects' normalized lift max. and their scores for peak force, height, and time-to-peak force. These analyses were conducted to determine the predictability of MAP by the power clean and back squat.

RESULTS AND DISCUSSION

For all subjects, multiple regression coefficients were strongest for associations between peak vertical force, time to peak vertical force, and jump height to the power clean scores (Table 1).

Lift	MR Coefficient			Probablity
PCleans	r = .947	r2 = .897	F = 37.7	P < .0001
Squats	r = .354	r2 = .125	F = .621	P< .613

Table 1. Multiple Regression Coefficients for All Subjects: Squat or Power Cleans with Three Dependent Variables.
df = 17; * statistically significant at < .05 level

The correlation between lift performances (squats vs. power cleans) was fairly weak (r = .291). This served as an indication that good squat performance does not necessarily translate to good power clean performance (Figure 1).

Figure 1. Squat-Power Clean Relationship (r = .291).

Although the better vertical jump performers were more proficient at performing the power clean lift, the strong correlation of r=.947 is misleading, as shown in Figure 2. The linearity of the scores come from the difference in jump performance between gender.

Figure 2. Correlation of Power cleans to height jumped (r = .932).

When examining the groups by gender, no significant differences were noted between the types of lifts and their correlation with the jump variables (Table 2). However, different trends were noted between gender. Women demonstrated much stronger correlations for the power clean scores and the jump variables, while the men demonstrated only slightly stronger correlations for the squat scores and the jump variables.

These research findings indicate that power clean performance is a better predictor of MAP than back squat performance for women, but not necessarily so for men. Hence, caution is urged when collapsing across gender. Replication is recommended to establish the reliability and generalizability of these findings.

Although the findings from one study do not provide evidence of causality, if the findings are replicable, coaches and trainers may have useful information regarding the strength/power modality yielding the best training adaptations needed for success in a highly anaerobic sport. The results of this research give coaches and trainers a better idea about utilizing back squats and power cleans for exercise prescriptions for their athletes and to not necessarily use the same prescription for men and women.

Lift	Male	Female
PCleans	r = .674	r = .746
Squats	r = .450	r = .768

Table 2. Comparison of Multiple Regression Coefficients By Gender for Squat or Power Cleans with Three Dependent Variables.
df = 7; no sig. differences found

REFERENCES

Beckenholdt, S.E., & Mayhew, J.L. (1983). Specificity among anaerobic power tests in male athletes. Journal of Sports Medicine, 23, 326-332.

Chandler,T.J., & Stone, M.H. (1991). The squat exercise in athletic conditioning: A review of the literature. National Strength and Conditioning Association Journal, 13(5), 52-29.

Enoka, R.M. (1979). The pull in Olympic weightlifting. Medicine and Science in Sports and Exercise, 11(2), 131-137.

Kraemer, W.J., & Fleck, S.J. (1987). Designing resistance training programs. Champaign, IL: Human Kinetics Books.

Poidomoni, M. (1991). Analysis of the countermovement vertical jump. Unpublished Masters Thesis: Western Michigan University.

ACKNOWLEDGMENTS

The authors wish to acknowledge and thank Bertec Force Plates for their support and also the Athletic Dept. and athletes of Utah State University for their help and support.