MECHANICAL AND ELECTROMYGRAPHICAL ANALYSIS OF A BOXER'S JAB

Abstract

INTRODUCTION Very little data exists about the mechanics of maximum force production of a boxeris jab. The purpose of this study was to determine the kinematics and muscular activity during a maximum force jab. Additionally, to determine if differences exist between professional (PRO) and amateurs (AM') boxers during recruitment of both the upper and lower body musculature. METHODS L Four PRO and five AMT boxers (age: 24.2k1.02 yrs; wgt: 81.7+ 8.13 kg; %BF: 11.99+2.6%) volunteered as subjects. Two dimensional kinematic data were collected with a Panasonic AG-500 video camera, operating at 30 Hz. Pre-amplified electrodes were placed on the gastrocnemius (GA), rectus femoris (RF), biceps femoris (BF), external oblique (EO), serratus anterior (SA), pectoralis major-sternal (PEC), anterior deltoid (AD), and tricep brachii (TRI). The EMG data and kinematic data were analyzed with the Ariel Performance Analysis System. Force measures were obtained from an instrumented boxing bag. Subjects performed three trials, after digitizing all trials, the trial with maximum linear velocity at the wrist was selected for further analysis. RESULTS Pearson product-moment correlations were conducted between the force production on the bag and muscle recruitment. The results indicate a significant relationship between force and the BF (r = .47), EO (r = .59) and PEC (r = .60). Tko-sample t-tests were conducted between PRO and AMT force and kinematic data. Significant differences (p < 0.05) were found in force production (t(6) = 2.65), wrist velocity (t(6) = 2.47) and elbow velocity (t(6) = 2.1 1). No significant differences were found between PRO and AMT recruitment of upper and lower body muscles. DISCUSSION The PRO boxers hit the bag harder with increased linear velocity of the wrist and elbow. Although no differences were found in muscle activation between the two groups, the duration and timing of the activation appears to favor the PRO. Because of the relationships found a weight training or resistance training program emphasizing leg extension, abdominal crunches, and shoulder flexion would assist the boxer in production of maximum force. The traditional conditioning program of a boxer (jumping rope, sit-ups, push-ups) would appear to address the boxers needs for both speed and force.