Previous research suggests high impact forces generated during landings contribute to noncontact anterior cruciate ligament (ACL) injuries. In women, neuromuscular differences appear to modify the ability to dissipate landing forces when compared to men. This study examined peak vertical impact forces (F(p)) and rate of force development (RFD) following a 9-week, low-intensity (simple jump-landing-jump tasks) and volume (number of foot contacts per workout) plyometric-based knee ligament injury prevention (KLIP) program. Female subjects were randomly assigned into control (n = 14) and treatment (n = 14) groups. Treatment subjects attended KLIP sessions twice a week for 9 weeks, and control subjects received no intervention. Ground reaction forces (F(p) and RFD) generated during a step-land protocol were assessed at study onset and termination. Significant reductions in F(p) (p = 0.0004) and RFD (p = 0.0205) were observed in the treatment group. Our results indicate that 9 weeks of KLIP training altered landing strategies in women to lower F(p) and RFD. These changes are considered conducive to a reduced risk of knee injury while landing.

Beneficial effects of McConnell medial glide taping may be related to factors other than altered patellar alignment.

In this study, we assessed the influence of training intensity on strength retention and loss incurred during detraining in older adults. In a previous study, untrained seniors (age = 71.0 +/- 5.0; n = 61) were randomly divided into 3 exercise groups and 1 control group. Exercise groups trained 2 days per week for 18 weeks with equivalent volumes and acute program variables but intensities of 2 x 15 repetitions maximum (RM), 3 x 9RM, or 4 x 6RM. Thirty of the original training subjects (age 71.5 +/- 5.2 years) participated in a 20-week detraining period. A 1RM for 8 exercises was obtained pre- and posttraining and at 6 and 20 weeks of detraining. The total of 1RM for the 8 exercises served as the dependent variable. Analysis of variance procedures demonstrated significant increases in strength with training (44-51%; p < 0.05), but no group effect. All training groups demonstrated significant strength decreases at both 6 and 20 weeks of detraining independent of prior training intensity (all group average 4.5% at 6 weeks and 13.5% at 20 weeks; p < 0.04). However, total-body strength was significantly greater than pretraining values after the detraining period (all group average 82% at 6 weeks and 49% at 20 weeks; p < 0.001). The results suggest that when older adults participate in progressive resistance exercise for 18 weeks, then stop resistance training (i.e., detrain), strength losses occur at both 6 and 20 weeks of detraining independent of prior resistance training intensity. However, despite the strength losses, significant levels of strength are retained even after 20 weeks of detraining. The results have important implications for resistance-trained older adults who could undergo planned or unplanned training interruptions of up to 5 months.

Limb dominance theory suggests that females tend to be more one-leg dominant and exhibit greater kinematic and kinetic leg asymmetries than their male counterparts, contributing to the increased risk of anterior cruciate ligament injury among female athletes. Thus, the purpose of this study was to examine the influences of sex and limb dominance on lower extremity joint mechanics during unilateral land-and-cut manoeuvres. Twenty-one women and 21 men completed land-and-cut manoeuvres on their dominant limb as well as their nondominant limb. Three-dimensional kinematics and kinetics were calculated bilaterally for the entire stance phase of the manoeuvre. Women performed land-and-cut manoeuvres with altered hip motions and loads as well as greater knee abduction at touchdown compared to men. Dominant limb land-and-cut manoeuvres where characterised by decreased hip flexion at touchdown as well as decreased hip flexion and adduction range of motion compared to nondominant land-and-cuts regardless of sex. The observed sex differences are consistent with previous research regarding mechanisms underlying the sex disparity in anterior cruciate ligament injury rates. However, observed differences regarding limb dominances appear somewhat arbitrary and did not suggest that the dominant or nondominant limb would be at increased risk of anterior cruciate ligament injury.

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Alterations in hip joint loading have been associated with diseases such as arthritis and osteoporosis. Understanding the relationship between gait speed and hip joint loading in healthy hips may illuminate changes in gait mechanics as walking speed deviates from preferred. The purpose of this study was to quantify hip joint loading during the gait cycle and identify differences with varying speed using musculoskeletal modeling. Ten, healthy, physically active individuals performed walking trials at their preferred speed, 10% faster, and 10% slower. Kinematic, kinetic, and electromyographic data were collected and used to estimate hip joint force via a musculoskeletal model. Vertical ground reaction forces, hip joint force planar components, and the resultant hip joint force were compared between speeds. There were significant increases in vertical ground reaction forces and hip joint forces as walking speed increased. Furthermore, the musculoskeletal modeling approach employed yielded hip joint forces that were comparable to previous simulation studies and in vivo measurements and was able to detect changes in hip loading due to small deviations in gait speed. Applying this approach to pathological and aging populations could identify specific areas within the gait cycle where force discrepancies may occur which could help focus management of care.