JOURNAL OF SPORTS SCIENCE & MEDICINE
THE RELATIONSHIP BETWEEN ISOMETRIC AND DYNAMIC STRENGTH IN COLLEGE FOOTBALL PLAYERS
Michael R. McGuigan1 and Jason B. Winchester2
1School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
2Department of Kinesiology, Louisiana State University, Baton Rouge, LA, USA.
© Journal of Sports Science and Medicine (2008) 7, 101 - 105
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|Previous research has demonstrated the importance of both dynamic
and isometric maximal strength and rate of force development (RFD) in athletic
populations. The purpose of this study was to examine the relationships
between measures of isometric force (PF), RFD, jump performance and strength
in collegiate football athletes. The subjects in this study were twenty-two
men [(mean ± SD):age 18.4 ± 0.7 years; height 1.88 ± 0.07 m; mass 107.6
± 22.9 kg] who were Division I college football players. They were tested
for PF using the isometric mid thigh pull exercise. Explosive strength was
measured as RFD from the isometric force-time curve. The one repetition
maximum (1RM) for the squat, bench press and power clean exercises were
determined as measures of dynamic strength. The two repetition maximum (2RM)
for the split jerk was also determined. Vertical jump height and broad jump
was measured to provide an indication of explosive muscular power. There
were strong to very strong correlations between measures of PF and 1RM (r
= 0. 61 - 0.72, p < 0.05). The correlations were very strong between
the power clean 1RM and squat 1RM (r = 0.90, p < 0.05). There were very
strong correlations between 2RM split jerk and clean 1RM (r = 0.71, p <
0.05), squat 1RM (r = 0.71, p < 0.05), bench 1RM (r = 0.70, p < 0.05)
and PF (r = 0.72, p < 0.05). There were no significant correlations with
RFD. The isometric mid thigh pull test does correlate well with 1RM testing
in college football players. RFD does not appear to correlate as well with
other measures. The isometric mid thigh pull provides an efficient method
for assessing isometric strength in athletes. This measure also provides
a strong indication of dynamic performance in this population.
Key words: Isometric strength, American football, power.
Previous research has demonstrated the importance of isometric maximal strength
(PF) and rate of force development (RFD) in a variety of athletic populations
including track cyclists (Stone et al., 2004),
track and field athletes (Stone et al., 2003b)
and weightlifters (Stone et al., 2005).
We have previously shown the value of measuring PF in college wrestlers
(McGuigan et al., 2006).
Generally there is no consensus in strength and conditioning regarding how
much strength is required for optimal performance in most sports (Stone
et al., 2002).
However research does suggest that the importance of maximum isometric strength
is underestimated in a variety of athletic populations (Stone et al., 2003a;
Previous research has investigated the strength and power characteristics of American football players (Black and Roundy, 1994; Fry and Kraemer, 1991). Maximum strength has been shown to discriminate between athletes of different performance levels within sports such as American football (Fry and Kraemer, 1991). The power clean, bench press and vertical jump were found to differentiate between various playing levels in college football (Fry and Kraemer 1991), although other researchers have found this is dependent on position and the type of test used (Black and Roundy, 1994). Although not applicable to some sports, having significant isometric strength may be advantageous for sports such as football and wrestling. However there is a lack of research examining the relationship between dynamic and isometric strength in football.
The isometric mid thigh pull test has been shown to correlate well with one- repetition maximum (1RM) testing in college wrestlers (McGuigan et al., 2006). This test was first described by Haff et al., 1997 and has shown to be highly reliable and reflect dynamic characteristics determined on jumping and 1RM tests. Similar relationships have been observed in a number of other sports including weightlifting (Haff et al., 2005; Stone et al., 2005), track cyclists (Stone et al., 2004) and track and field athletes (Stone et al., 2003b). As there is a high force and power component associated with American football, it would seem likely that similar relationships between static and dynamic performance may exist. Therefore the purpose of this investigation was to examine the relationships between measures of PF, RFD, jump performance and strength in collegiate football players.
The results of the tests were given in Table 1. There were strong to very strong correlations between measures of PF and 1RM (r = 0.61 - 0.72). The correlations were nearly perfect between the power clean 1RM and squat 1RM (r = 0.90). There was a strong correlation between 1RM squat and vertical jump (r = 0.54). There were very strong correlations between 2RM split jerk and clean 1RM (r = 0.71), squat 1RM (r = 0.71), bench 1RM (r = 0.70) and PF (r = 0.72). There were strong to very strong correlations between body mass and clean 1RM (r = 0.45), bench 1RM (r = 0.78), broad jump (r = -0.60), 2RM split jerk (r = 0.57) and PF (r = 0.53). There were no other significant correlations with other variables and no significant correlations with RFD.
Previous research has demonstrated the important
role of isometric strength to performance across a range of different
sports (Stone et al., 2003b;
2005, McGuigan et al., 2006).
The results of this study indicate that in collegiate football athletes
the isometric mid thigh pull test does correlate well with 1RM testing.
However, RFD was shown to be not as critical in relation to maximal strength
in these athletes. These results suggest that isometric testing provides
a good indication of an athlete's dynamic performance during 1RM testing,
including the back squat, power clean, bench press and split jerk exercises.
|American football is a sport that requires high levels of both strength and power. The isometric mid thigh pull test does correlate well with 1RM testing for the power clean, squat and bench press and the 2RM for the split jerk. RFD does not appear to be as important in college football. The isometric mid thigh pull provides an efficient method for assessing isometric strength in athletes. Given that isometric strength may potentially differentiate between successful and less successful athletes (Stone et al., 2002), this test can provide important information in the strength diagnosis of football players. This measure also provides a strong indication of dynamic performance in this population. The lack of strong correlations with other variables such as RFD may be a result unique strength and power capacities represented by those specific tests. This highlights the importance of assessing and training these unique capacities and not relying on one single test such as a 1RM test to provide a strength profile of an athlete.|
|The authors would like to that the members of the Louisiana State University football team for their cooperation and assistance with the study.|
Michael R. McGUIGAN
Employment: Senior Lecturer in the School of Exercise, Biomedical and Health Sciences at Edith Cowan University.
Research interests: Physiological responses to resistance training and monitoring training.
Jason B. WINCHESTER
Employment: Doctoral Student at Louisiana State University.
Research interests: Sport physiology, neuromuscular plasticity, biomechanics of power activities, and stretching and performance.