Date of Award

2014

Degree Type

Thesis

Degree Name

Master of Science (Sports Science)

School

School of Exercise and Health Sciences

Faculty

Faculty of Health, Engineering and Science

First Advisor

Dr Fadi Ma'ayah

Second Advisor

Associate Professor Anthony Blazevich

Abstract

Football is the most widely played sport in the world and is thus associated with the highest total number of injuries of all sports. 12% of all football injuries are to the hamstrings, as this muscle group is subjected to constant stress during training and match play performance (Ekstrand, Hägglund, Waldén, 2011; Woods, Hawkins, Maltby, Hulse, Thomas & Hodson, 2004). While the influence of limb dominance has been extensively examined as a risk factor for injury in upper limb-dominant sports (e.g. badminton, tennis and baseball), little research has focussed on the dominance in the lower limbs. Since almost all footballers show a limb preference for kicking, an example of limb dominance, it is possible to speculate that limb-specific injury rates will vary between preferred and non-preferred legs (Brophy, Silvers, Gonzales and Mandelbaum, 2010). Previous research has also shown that injury rates increase with the accumulation of fatigue, and that inter-limb force production variation increases as fatigue progresses. Thus, the possibility exists that increases in inter-limb force production variability after fatiguing exercise would increase injury risk in football players. The purpose of the present research, therefore, was to examine changes in muscle force production and fatigue between preferred and non-preferred legs in football players with and without a history of unilateral hamstring injury (in the preferred kicking leg). In the single leg vertical jump, peak jump force of the preferred leg in the injured group changed by -12% whilst force in the non-preferred leg changed by -5%. Force in the non-injured preferred leg changed by -6% and changed by -8% in the non-preferred leg. These results indicate a clear difference in fatigue response between groups, and that the inter-limb difference in force production is greater in the preferred leg of the injured group. Decline in hamstring torque in the preferred leg of the injured group changed by 98%, and the non-preferred leg changed by 67%. While in the non-injured group, decline in hamstring torque changed by 219% and 852% respectively. The greater changes observed in the non-injured group was due to minimal fatigue before the fatigue condition (repeated-sprint test). The injured group had a greater fatigue response both before and after the fatigue condition (26.1±18.4 to 51.7±20.9 N preferred leg and 11.6±8.94 to 19.4±20.5 N non-preferred leg) suggesting previous injury has a different effect on fatigue response. Horizontal force production during the repeated-sprint test changed by -14% in the preferred kicking leg and -3% in the non-preferred leg (injured group). This represents the preferred kicking leg having a greater fatigue response. In conclusion, the present study has provided a foundation for comparing the injured and non-injured group and the preferred and non-preferred kicking legs during a single leg vertical jump, isokinetic endurance test and repeated-sprint test. These tests provided evidence that the non-preferred leg had greater force production, the preferred leg had greater fatigue response, and the inter-limb difference in force production after fatigue was greater in the injured group. It can be assumed that the preferred kicking leg of the injured group being the previously injured leg has attributed to these results. These results highlights the need for future research to further understanding of the differences in preferred and non-preferred kicking legs, why they occur, and the influence they have on injury

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