Changes In Vertical Ground Reaction Forces Research Articles

The Effects of a Multimodal Rehabilitation Program on Symptoms and Ground-Reaction Forces in Runners With Patellofemoral Pain Syndrome.

Patellofemoral pain (PFP) is one of the most frequent running-related injuries. However, few interventions taking into consideration the specificity of running have been shown to be effective in runners with PFP. To evaluate the effects of a multimodal rehabilitation program including lower-limb-strengthening/ motor-control exercises, advice on running biomechanics, and symptoms management on symptoms, strength, and ground-reaction forces in runners with PFP. Pre- to post- quasi-experimental. Gait-analysis laboratory and private physical therapy clinic. 21 runners with PFP (34.1 ± 6.0 y old, symptoms duration 38.1 ± 45.5 mo). An 8-wk multimodal rehabilitation program including lower-limb- and core-strengthening and motor-control exercises, as well as advice on running gait and symptoms management. The Activities of Daily Living Scale of the Knee Outcome Survey (KOS-ADLS) questionnaire and visual analog scales for usual pain (VAS-U), worst pain (VAS-W), and pain during running (VAS-R) were used to assess changes in symptoms and function. Vertical ground-reaction forces (VGRF) during running and lower-limb isometric strength were also measured. Statistically and clinically significant improvements (P < .001) were reported on KOS-ADLS (+17.8 pts), VAS-U (-19.2 pts), VAS-W (-28.7 pts), and VAS-R (-32.2 pts) after the intervention. No significant changes in isometric strength were observed. The instantaneous vertical loading rate was decreased after the intervention (P = .002), and this reduction was correlated with changes in KOS-ADLS scores (P = .028). This multimodal intervention was successful in reducing pain and improving function of runners with PFP. However, no significant changes in lower-limb strength were observed. It appears that changes in VGRF combined with appropriate training advice could explain the clinical outcomes.

Unloading reaction during sudden ankle inversion in healthy adults

The purpose of this research study was to determine the dynamics of early human response from sudden ankle inversion (30° tilt). Changes in vertical ground reaction forces (GRFs) following trapdoor release in a group of healthy subjects were compared to those from the similar experiments using a chair with two U shaped steel legs and matched weights of the human subjects. The experiments with the chair were further repeated with additional foam paddings at their bases to introduce visco-elastic properties to legs of the chair. Following the trapdoor release a decrease in the vertical ground reaction force under the inverting leg and subsequent increase in the supporting leg were observed in both human and chair experiments. The short onset of changes in vertical GRFs in our experiments indicate that the dynamic features of early response following trapdoor release are primarily due to mechanical events and may not be significantly affected by the neuromuscular reaction of human subjects.

Lower Extremity Kinematics and Ground Reaction Forces After Prophylactic Lace-Up Ankle Bracing

Long-term effects of ankle bracing on lower extremity kinematics and kinetics are unknown. Ankle motion restriction may negatively affect the body's ability to attenuate ground reaction forces (GRFs). To evaluate the immediate and long-term effects of ankle bracing on lower extremity kinematics and GRFs during a jump landing. Experimental mixed model (2 [group] x 2 [brace] x 2 [time]) with repeated measures. Sports medicine research laboratory. A total of 37 healthy subjects were assigned randomly to either the intervention (n = 11 men, 8 women; age = 19.63 +/- 0.72 years, height = 176.05 +/- 10.58 cm, mass = 71.50 +/- 13.15 kg) or control group (n = 11 men, 7 women; age = 19.94 +/- 1.44 years, height = 179.15 +/- 8.81 cm, mass = 74.10 +/- 10.33 kg). The intervention group wore braces on both ankles and the control group did not wear braces during all recreational activities for an 8-week period. Initial ground contact angles, maximum joint angles, time to reach maximum joint angles, and joint range of motion for sagittal-plane knee and ankle motion were measured during a jump-landing task. Peak vertical GRF and the time to reach peak vertical GRF were assessed also. While participants were wearing the brace, ankle plantar flexion at initial ground contact (brace = 35 degrees +/- 13 degrees , no brace = 38 degrees +/- 15 degrees , P = .024), maximum dorsiflexion (brace = 21 degrees +/- 7 degrees , no brace = 22 degrees +/- 6 degrees , P = .04), dorsiflexion range of motion (brace = 56 degrees +/- 14 degrees , no brace = 59 degrees +/- 16 degrees , P = .001), and knee flexion range of motion (brace = 79 degrees +/- 16 degrees , no brace = 82 degrees +/- 16 degrees , P = .036) decreased, whereas knee flexion at initial ground contact increased (brace = 12 degrees +/- 9 degrees , no brace = 9 degrees +/- 9 degrees , P = .0001). Wearing the brace for 8 weeks did not affect any of the outcome measures, and the brace caused no changes in vertical GRFs (P > .05). Although ankle sagittal-plane motion was restricted with the brace, knee flexion upon landing increased and peak vertical GRF did not change. The type of lace-up brace used in this study appeared to restrict ankle motion without increasing knee extension or vertical GRFs and without changing kinematics or kinetics over time.