RELATIONSHIP OF GRIP STRENGTH AND FOREARM SIZE TO BAT VELOCITY IN COLLEGE FEMALE SOFTBALL PLAYERS
by
Drew Giardina, Heather Leslie, Lezlie Raridon, and Dan Zimmer
Exercise Science Program, Truman State University, Kirksville, MO

Original Publication Information:
IAHPERD Journal Volume 30. No.2 Spring, 1997.
INTRODUCTION
Most research in the field of baseball and softball has been done to investigate the relationship to the properties of throwing the ball. Little research has been completed to determine the various aspects of swinging a bat. While throwing is a major portion of the game, hitting is becoming increasingly important. Hitting for power and higher averages are what are more important in today's game.

One of the main focuses in hitting is the quickness with which a player can "get around on the ball". This concept may be even more important in the game of softball than in baseball. Decreasing the amount of time it takes to swing the bat will enable the female softball athlete to have more time to decide whether to attempt to hit the ball.

Past research has also shown that the faster a bat is swung, the more force that can be applied to the ball causing it to travel farther in flight, all other factors being equal. Therefore, identifying factors that can increase bat velocity may increase hitting productivity. The purpose of this study was to determine the relationship of grip strength (GS) and forearm size to softball bat velocity.

METHODS
Eighteen female college varsity softball players (age = 20.3 yrs; weight = 162 lbs) with a minimum of five years of competitive experience were used in the study. An electronic timing system was used to measure the time interval of each bat swing through a 0.54 m space over home plate. The system consisted of two infrared cells attached to a digital timer. Following five practice swings, each player was measured for three trials, and the average bat velocity used for all analyses.

Three right and three left isometric GS measurements were taken on each subject using a Jaymar hand dynamometer. The dynamometer was held to the side of the body with slight flexion at the elbow to maximize results (Vanderburgh, Mahar & Chou, 1995). Trials were done alternating hands to decrease fatigue, with approximately 45 seconds rest between each trial. The average for each hand was used. Right and left forearm circumferences were taken around the maximum girth immediately distal to the elbow. Forearm skinfold (SKF) measurements were taken on the lateral aspect of each forearm while in the anatomical position. These values were used to calculate right and left cross-sectional area (CSA) according to the following formula:

CSA (cm2) = [(Circumference - (pi)SKF/2)2] / 4(pi)

RESULTS
There were no significant relationships between bat velocity and any size or strength measurements (Table 1). The relationship between bilateral measurements were positive and significant, indicating symmetry in size and strength.

Table 1. Means And SD For Performance Characteristics Of The Subjects (n= 18).
Variable Mean SD Range
Bat Speed (m*s-1) 20.5 2.2 15.9 - 24.6
L Grip Str (kg) 38.1 5.5 30.1 - 48.0
R Grip Str (kg) 41.0 4.5 30.7 - 51.3
L CSA (cm2) 42.8 5.1 33.6 - 56.2
R CSA (cm2) 45.0 5.6 35.5 - 56.2
DISCUSSION
The current study agrees with Adair's theory that the torque applied by the hands and wrist during the bat swing are negligible (Adair, 1994; Adair, 1995). This may suggest that increases in either or both grip strengths beyond a minimal amount will have no effect on enhancing bat velocity. Performing exercises such as forearm curls to increase forearm CSA and strength will not have a measurable effect on bat swing velocity.

The current results may indicate that other factors not examined in this study may have more effect on bat velocity. Adair (1994) suggests that the energy for the swing must come largely from the large muscles of the thighs and thorax. The rotational force generated by these large muscles are then transferred to the arms for the swing in a carefully orchestrated summation of forces (Shaffer, Jobe, Pink, & Perry, 1993). Previous research has suggested that strengthening the triceps brachii muscles of the lead arm may increase bat velocity to a greater extent than grip strength (Kitzman, 1964). It would be worthwhile to determine the contributions of arm extensor strength and trunk rotational forces on batting performance (Shaffer et al., 1993).

Effective batting may be more dependent on coincident anticipation timing of the bat to contact the ball over the plate than on strength (Mikel, 1984). Therefore, future research might include measures of both anticipation time and trunk rotational and/or arm extension strength. Identifying the contribution of these factors might provide ground work for the development of conditioning programs to improve hitting.

Table 2. Correlations Of Size And Strength Measurements To Bat Velocity (n= 18).
Variable 2 3 4 5
Bat Speed (m*s-1) - 0.71 - 0.04 0.23 - 0.05
Left Grip (kg) 0.83 0.58 0.65
Right Grip (kg) 0.51 0.57
Right CSA (cm2) 0.87
Left CSA (cm2)
r = 0.47 significant at p<0.05.
REFERENCES