Abstract
Background:
Sport specialization has been associated with increased risk of both acute and chronic lower extremity musculoskeletal injuries in adolescent athletes. Repetitive movement through sport specialization has been hypothesized to increase the stress through the lower extremity, leading to injury. However, the underlying mechanism is unclear.
Purpose:
The purpose of this study was to examine the differences in sagittal plane lower extremity loading between adolescent athletes who participate in a single sport (SS) verse those who participate multiple sports (MS).
Methods:
A cross sectional study design was used. A total 252 adolescent athletes participated in the study (Males: SS=26, Age=14.62±1.72, Ht=173.06±12.41 cm, Mass =62.47±14.72 Kg; MS=27, Age=13.52±1.72, Ht=171.61±11.20 cm, Mass =61.32±14.21 Kg Females: SS=127, Age=14.28±1.77, Ht=164.72±10.73 cm, Mass =58.29±11.17 Kg, MS=84, Age=13.62±1.41, Ht=163.22±7.67 cm, Mass =57.63±11.44 Kg). Participants were included if they were between the ages of 10 and 17, involved in high-risk sports for equal or greater than 50 hours per year, and reported no injuries in the 3 months prior to participation in the study. Joint moments of the hip, knee, and ankle were assessed at initial contact (IC) during a jump-landing (JL) task in both the dominant and non-dominant limbs. All values were normalized to the product of height and weight and averaged across three trials. Participants were grouped into SS or MS groups, then sub-grouped by gender. Separate independent t-tests were performed on each dependent variable for the dominant and non-dominant limbs in males and females to examine the differences between the groups (SS vs MS) (α = 0.05).
Results:
In the female cohort, the SS group demonstrated lesser knee flexion moments compared to the MS group on dominant side (SS=0.022 HtWt-1, MS=0.026 HtWt-1; p=0.012). The female SS group also demonstrated lesser hip extension moments (SS=0.031HtWt-1, MS=0.042 HtWt-1; p=0.022) and knee flexion moments on non-dominant side compared to that of the MS group (SS=0.023HtWt-1, MS=0.027 HtWt-1; p=0.013). There were no significant differences observed in any of the variables in male adolescents.
Conclusion:
Altered sagittal plane biomechanics were observed in female adolescents, but not in male adolescents during a JL task. The MS group had greater loading at the hip and knee joints than the SS group. Since MS has been suggested to increase the risk of lower extremity injuries, this biomechanical pattern at IC of a JL may be a profile for higher risk of lower extremity injuries. (394/400)
Sagittal plane moment at initial contact during jump-landing task.
| Single sport (SS) | Multiple sports (MS) | p-value | ||
|---|---|---|---|---|
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| Dominant | Hip | 0.037±0.040 | 0.038±0.040 | 0.094 |
| Knee | 0.028±0.015 | 0.027±0.015 | 0.096 | |
| Ankle | 0.0001±0.0007 | -0.0001±0.001 | 0.741 | |
| Non-Dominant | Hip | 0.036±0.040 | 0.041±0.028 | 0.061 |
| Knee | 0.026±0.017 | 0.028±0.012 | 0.611 | |
| Ankle | -0.0002±0.0006 | -0.0002±0.0012 | 0.915 | |
|
|
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| Dominant | Hip | 0.029±0.034 | 0.038±0.032 | 0.057 |
| Knee | 0.022±0.013 | 0.026±0.012 | 0.012* | |
| Ankle | 0.088±0.021 | 0.092±0.021 | 0.14 | |
| Non-Dominant | Hip | 0.031±0.034 | 0.042±0.032 | 0.022* |
| Knee | 0.023±0.012 | 0.028±0.012 | 0.013* | |
| Ankle | -0.0004±0.0008 | -0.0002±0.0018 | 0.279 | |
* indicates significant difference between the groups.