The effect of sex and age on lower extremity muscle co-contraction during walking and running
LE3 .A278 2018
Bachelor of Kinesiology
Osteoarthritis (OA) of the knee is the leading cause of walking disability in the elderly population. Early-onset of knee OA is becoming increasingly more prevalent as acute knee injuries such as anterior cruciate ligament (ACL) tears have the potential to influence the onset and progression of the disease. Females are at 2-8 times greater risk of sustaining an ACL tear and roughly 50% of those who do will develop knee OA within 10-20 years. Co-contraction has been identified as a critical factor to reduce or prevent excessive joint movement and loads that may increase one’s risk of sustaining an ACL injury. While ACL injuries do not normally occur during mundane forms of locomotion, individuals who demonstrate neuromuscular patterns suggestive of potential harm during these activities are likely to reproduce them during athletic maneuvers. Analyzing the co-contraction of the lower-extremity muscles during walking and running may help to identify those at increased risk of sustaining an ACL injury and consequently, developing OA. This knowledge may be valuable in facilitating and enhancing OA and injury prevention programs. The study was designed to investigate differences in dominant leg co-contraction indexes (CCIs) of quadriceps, hamstrings and gastrocnemius muscle pairings during walking and running in pre- and post-pubescent male and female athletes. Participants (male=65, female=67) were recruited from Acadia University varsity programs and local youth sport organizations. Of the females, 28 were categorized as pre-pubescent (age = 10.93yr±1.53) and 39 categorized as post- pubescent (age = 18.69 yr±2.49). Of the males, 32 were categorized as pre-pubescent (age = 10.41 yr±1.90) and 33 were categorized as post-pubescent (age = 18.73 yr±3.56). Muscle activation patterns were analyzed using 16 wireless EMG electrodes, a 13-camera motion capture system, and 3 force plates. Two-way between subjects ANOVAs (p ≤ 0.05) were used to compare the effect of sex (males versus female) and age (pre-versus post-pubescent) on group average CCIs during the first and second halves of stance phase for walking and running trials. Results showed the pre-pubescent male and female participant groups had significantly higher average CCIs for all four muscle pairings studied (medial hamstring (MH)/vastus medialis (VM), lateral hamstring (LH)/vastus lateralis (VL), lateral gastrocnemius (LG)/vastus lateralis (VL), and medial gastrocnemius (MG)/vastus medialis (VM)) during the first half of walking stance and for the LH/VL muscle pairing during the second half of walking stance. As co-contraction of the lower-extremity muscles is suggested to increase stability of the knee joint, these findings may provide insight into why individuals of the pre-pubescent age appear to be at lower risk of injury. The results also found female participants to have higher group average CCIs for five of the six significant sex effects. The female participants of this study showed higher co- contraction of the thigh musculature compared to the male participants, indicating that the well-documented quadriceps: hamstring deficiently was not present in the female athletes of this study. However, female participants did show higher co-contraction of the MG/VM muscle pairing during the first and second halves of running stance when compared to the male participants, which is suggested to place higher strain through the ACL. These findings provide some insight into the influence that co-contraction may have as a prevention and risk factor for non-contact ACL injuries in athletes.
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