vGRF force feedback decreased the second peak vertical ground reaction force during loaded walking, but participants adopted a crouched gait pattern that increased both first and second peak tibiofemoral joint contact forces.
Key Findings
Results
Participants significantly decreased the second peak vertical ground reaction force (vGRF) and vGRF impulse when given peak vGRF feedback, but not the first peak vGRF.
Twenty-four participants walked at 1.4 m·s-1 with vest-borne loads of 0%, 15%, and 30% body weight
Feedback was provided on the average peak vGRF for each leg in two-second epochs during each of six conditions
The first peak vGRF was not significantly reduced with feedback
Both the second peak vGRF and vGRF impulse were significantly reduced with feedback
Results
Despite reductions in vGRF, participants increased both first and second peak tibiofemoral joint (TFJ) contact forces when given vGRF feedback.
The adopted gait pattern in response to feedback was a crouched pattern with increased knee flexion
Increased knee flexion led to greater quadriceps demand
Both first and second peak TFJ contact forces were increased with feedback across conditions
Results
vGRF and TFJ contact forces increased directly with increased vest-borne load in both feedback and no-feedback conditions.
Three load conditions were tested: 0%, 15%, and 30% body weight added via vest
The increase in forces with load was observed regardless of whether feedback was provided
This dose-response relationship held for both vGRF and TFJ contact force measures
Results
vGRF feedback did not lead to decreased TFJ contact forces during load carriage walking despite successfully modifying ground reaction forces.
The study purpose was to investigate whether vGRF feedback could decrease peak TFJ contact force and impulse via gait adaptations
The crouched gait pattern adopted by participants counteracted any potential benefit to joint loading from reduced vGRF
Authors concluded that 'vGRF force feedback represents an intuitive tool for modifying walking mechanics, but when employed to decrease ground reaction forces during load carriage in this study, it did not lead to decreased TFJ contact forces'
Discussion
Future strategies aimed at decreasing joint load should target primary contributors of joint load such as knee extensor moments, quadriceps force, or joint contact forces directly.
The authors identified knee extensor moments, quadriceps force, and joint contact forces as primary contributors to TFJ loading
Indirect feedback targeting vGRF was insufficient to reduce joint loading due to compensatory gait changes
The authors suggest that direct biofeedback targeting these primary contributors may be more effective
What This Means
This research suggests that giving people real-time feedback about how hard their feet hit the ground during walking—a measure called vertical ground reaction force (vGRF)—can successfully reduce certain aspects of that impact force. In a study of 24 participants walking on a treadmill while carrying vest-borne loads equivalent to 0%, 15%, and 30% of their body weight, feedback caused participants to reduce the second peak force of each footstep and the overall force impulse. However, the way participants changed their walking to achieve this reduction actually backfired in terms of joint health.
Participants responded to the feedback by adopting a more 'crouched' walking posture with greater knee bending. While this reduced the ground reaction force, it required the quadriceps muscles (the large muscles at the front of the thigh) to work harder to support the bent-knee position. This increased muscle activity placed greater compressive force on the tibiofemoral joint—the main joint of the knee where the thighbone meets the shinbone—actually increasing knee joint loading rather than decreasing it. This effect occurred across all load conditions tested.
This research suggests that for people who need to reduce knee joint stress—such as those with knee osteoarthritis or military personnel carrying heavy loads—simply targeting ground reaction force with biofeedback may not be the right approach. The compensatory movement strategies people naturally adopt can offset or even worsen the intended benefit. Instead, future interventions may need to provide feedback more directly tied to the forces acting on the knee joint itself, such as targeting the knee extensor muscle forces or joint contact forces, to achieve meaningful reductions in joint loading.
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Jones B, Willson J, DeVita P, Wedge R. (2026). Tibiofemoral contact forces during walking with and without peak vertical ground reaction force feedback.. Journal of biomechanics. https://doi.org/10.1016/j.jbiomech.2026.113375