Effect of Footwear on Dynamic Stability during Single-leg Jump Landings.

Barefoot and minimal footwear running has led to greater interest in the biomechanical effects of different types of footwear. The effect of running footwear on dynamic stability is not well understood. The purpose of this study was to compare dynamic stability and impact loading across 3 footwear conditions; barefoot, minimal footwear and standard running shoes. 25 injury free runners (21 male, 4 female) completed 5 single-leg jump landings in each footwear condition. Dynamic stability was assessed using the dynamic postural stability index and its directional components (mediolateral, anteroposterior, vertical). Peak vertical ground reaction force and vertical loadrates were also compared across footwear conditions. Dynamic stability was dependent on footwear type for all stability indices (ANOVA, p<0.05). Post-hoc tests showed dynamic stability was greater when barefoot than in running shoes for each stability index (p<0.02) and greater than minimal footwear for the anteroposterior stability index (p<0.01). Peak vertical force and average loadrates were both dependent on footwear (p≤0.05). Dynamic stability, peak vertical force, and average loadrates during single-leg jump landings appear to be affected by footwear type. The results suggest greater dynamic stability and lower impact loading when landing barefoot or in minimal footwear.

Greater vertical impact loading in female runners with medically diagnosed injuries: a prospective investigation.

BACKGROUND: Running has been critical to human survival. Therefore, the high rate of injuries experienced by modern day runners is puzzling. Landing on the heel, as most modern day shod runners do, results in a distinct vertical impact force that has been shown to be associated with running-related injuries. However, these injury studies were retrospective in nature and do not establish cause and effect. OBJECTIVE: To determine whether runners with high impacts are at greater risk for developing medically diagnosed injuries. METHODS: 249 female runners underwent a gait analysis to measure vertical instantaneous loading rate, vertical average loading rate (VALR), vertical impact peak (VIP) and peak vertical force. Participants then recorded their mileage and any running-related injuries monthly in a web-based, database programme. Variables were first compared between the entire injured (INJ; n=144) and uninjured (n=105) groups. However, the focus of this study was on those injured runners seeking medical attention (n=103) and those who had never injured (n=21). RESULTS: There were no differences between the entire group of injured and uninjured groups. However, all impact-related variables were higher in those with medically diagnosed injuries compared with those who had never been injured. (effect size (ES) 0.4-0.59). When VALR was >66.0 body weight (BW)/s, the odds of being DX_INJ were 2.72 (95% CI 1.0 to 7.4). Impact loading was associated with bony and soft-tissue injuries. CONCLUSIONS: Vertical average loading rate was lower in female runners classified as 'never injured' compared with those who had been injured and sought medical attention.

Effects of Overweight and Obesity on Running Mechanics in Children.

PURPOSE: The purpose of this study is to determine differences in running mechanics between healthy weight (HW) children and children classified as OW/OB. METHODS: Forty-two children (17 OW/OB, 25 HW) ran overground while kinematic and kinetic data were recorded using a motion capture system and force plate. Kinematic variables of interest included stance time, step length, and frontal and sagittal plane joint angles and excursions at the hip, knee, and ankle. Kinetic variables of interest included ground reaction forces and hip, knee, and ankle moments in the sagittal and frontal planes. RESULTS: The OW/OB group spent more time in stance, took shorter steps, displayed less hip flexion during the first half of stance, had greater ankle inversion at foot strike, had greater knee abduction throughout stance, and had smaller knee flexion, knee adduction, and hip adduction excursions. In comparing unscaled ground reaction forces, the OW/OB group displayed greater peak vertical force, vertical impact peaks, and vertical loading rates. The OW/OB group also displayed greater unscaled plantar and dorsiflexion moments, knee flexion and extension moments, ankle inversion moments, and knee and hip abduction moments. CONCLUSION: These data suggest that increased body weight in children is associated with changes in running mechanics. Higher joint moments and ground reaction forces may indicate increased injury risk or the development of joint degeneration among overweight/obese children.

Reducing Impact Loading in Runners: A One-Year Follow-up.

Increased vertical impact loading during running has been associated with a variety of running related injuries including stress fractures, patellofemoral pain, and plantar fasciitis. PURPOSE: The purpose of this study was to examine the acute and long-term effect of a gait retraining program aimed at teaching runners with high impact loading to run softer. METHODS: Nineteen runners with high tibial shock (TS) first underwent a control period of eight sessions of treadmill running over 2 wk, progressing from 15 to 30 min. This was followed by eight sessions of gait retraining over 2 wk using the identical treadmill protocol. Real-time feedback of TS was provided as the participant ran. Feedback was gradually removed during the last four sessions. Variables of interest included peak TS, vertical impact peak and vertical average loading rate, and vertical instantaneous loading rate. These variables were assessed at intervals following the retraining and at a 1-yr follow-up. RESULTS: All variables of interest were significantly reduced post-retraining (P < 0.001). TS was reduced by 32%, vertical impact peak by 21%, vertical instantaneous loading rate by 27%, and vertical average loading rate by 25%. All variables continued to be significantly reduced at a 1-yr follow-up. CONCLUSIONS: Impact loading can be reduced through gait retraining and the results persist at least 1 yr. As impact loading is associated with injury, this simple intervention may provide a powerful method of reducing musculoskeletal injury risk in runners.