Document Type : Research Paper
Authors
1
Department of Sport sciences, Faculty of Sport Sciences, University of Birjand, Birjand, Iran
2
Department of Sport sciences, Faculty of Humanities, Lorestan University, Khorramabad, Iran
Abstract
Background and Purpose
Since the emergence of COVID-19 caused by SARS-CoV-2, millions worldwide have suffered not only from acute respiratory symptoms but also from long-term multisystem complications, including neurological, cardiovascular, and musculoskeletal sequelae. Older adults represent the most vulnerable cohort, often enduring prolonged hospitalization, reduced physical activity, and subsequent neuromuscular decline. These factors may impair motor control, balance, and gait mechanics even after clinical recovery. Gait is a critical functional indicator of neuromuscular and musculoskeletal integrity, commonly assessed by ground reaction forces (GRFs), which quantify the multi-directional forces exerted between the foot and the ground specifically vertical, anterior, posterior, medial and lateral components. GRFs serve as sensitive measures of balance, propulsion, and stability, detecting subtle gait deficits not apparent through observational analysis. Prior research suggests persistent gait alterations in individuals’ post-COVID-19, including diminished force output and asymmetries; however, investigations focusing on elderly populations remain scarce. This study aimed to compare GRF parameters during walking between elderly men with and without prior COVID-19 infection.
Methods
This semi-experimental, cross-sectional study recruited 30 elderly men aged 65 to 80 years from clinical centers in Ardabil, Iran. Participants were assigned to two groups: COVID-19 group (n = 15), comprising individuals with laboratory-confirmed COVID-19 infection, hospitalized for 19–23 days, and recovered at least one month before testing; and healthy control group (n = 15) without COVID-19 history. Inclusion criteria for the COVID-19 group included absence of musculoskeletal injuries or surgeries affecting gait, no intra-articular injections or performance-enhancing drugs within the preceding three months, and no neurological disorders. Exclusion criteria for both groups included uncontrolled hypertension, recent myocardial infarction or stroke, unstable angina, severe visual impairment, or unwillingness to participate.
GRFs were measured using a Bertec force platform (USA) with a 1000 Hz sampling frequency. Participants walked barefoot along a 20-meter walkway with the force plate embedded at the midpoint. Familiarization trials ensured natural gait patterns without targeting the force plate. Trials were valid when the entire foot contacted the plate without stride adjustment. Each participant completed five valid self-selected speed trials. Dominant leg was identified via a ball-kicking test. Raw GRF data were processed using a fourth-order Butterworth low-pass filter at a 50 Hz cutoff.
Data normality was assessed using the Shapiro–Wilk test. Independent samples t-tests compared group means for all variables with significance set at p < 0.05. Effect sizes (Cohen’s d) were calculated to evaluate difference magnitudes.
Results
Compared to controls, the COVID-19 group exhibited a significantly longer time to the first vertical GRF peak (TTPFzHC) (+21.5%, p = 0.030, d = 0.23). Peak GRF magnitudes at heel-strike and push-off did not differ significantly (p > 0.05). The propulsive peak at push-off (FyPO) was significantly reduced in the COVID-19 group (−28.3% versus controls; p = 0.031, d = 0.28). No group differences existed for braking peaks or associated times. Medial–lateral GRF peaks and times showed no significant differences (p > 0.05). Although the COVID-19 group had a slightly lower mean vertical loading rate, this did not reach significance (p = 0.153, d = 0.23).
Center-of-pressure (COP) displacement analysis revealed significantly greater anterior–posterior displacement (COPy) in the COVID-19 group (+47.2%, p = 0.002, d = 0.50), indicating reduced anterior–posterior stability. No significant differences appeared in medial–lateral COP displacement (COPx) or COP velocities.
Conclusion
Elderly men with a history of COVID-19, despite full recovery and absence of overt gait disabilities, demonstrate measurable kinetic alterations during level walking. Key findings include delayed attainment of the initial vertical GRF peak, decreased anterior–posterior propulsive forces during push-off, and elevated anterior–posterior COP displacement—a biomechanical signature of impaired balance. These changes suggest adoption of a cautious gait strategy, potentially compensating for reduced muscular strength, proprioceptive deficits, or lingering vestibular dysfunction. The absence of significant differences in medial–lateral GRF and COP suggests greater vulnerability of anterior–posterior stability in this population. Clinically, findings emphasize the need for targeted rehabilitation focusing on lower-limb extensor and plantar flexor strengthening, anterior–posterior balance enhancement, and gait efficiency improvement. Despite limitations including small sample size and cross-sectional design, results suggest COVID-19 may impart subtle yet consequential biomechanical alterations that, if unaddressed, could increase fall risk, underscoring the importance of proactive assessment and intervention in geriatric care.
Article Message
This study demonstrates that elderly individuals’ post-COVID-19 exhibit notable gait and balance impairments relative to healthy counterparts. Specifically, they show diminished anterior–posterior stability and reduced propulsive forces, indicating compensatory locomotor adaptations. These findings reinforce the need for rehabilitation programs emphasizing muscular strengthening and balance retraining to reduce fall risk and support functional independence in this vulnerable population.
Ethical Considerations
All research protocols involving human participants adhered strictly to ethical standards and received approval from the Ethics Committee of Birjand University (Approval ID: IR.BIRJAND.REC.1403.010). Participant rights, safety, and confidentiality were rigorously protected.
Authors’ Contributions
Conceptualization: Ilbeigi, Yousefvand, Bagheri, Yousefi
Data Collection: Ilbeigi, Yousefvand, Bagheri
Data Analysis: Ilbeigi, Bagheri
Manuscript Writing: Ilbeigi, Yousefvand
Review and Editing: Ilbeigi
Funding Responsibility: Not specified
Literature Review: Ilbeigi, Yousefvand
Project Management: Ilbeigi, Bagheri, Yousefi
Conflict of Interest
The authors declare no conflicts of interest related to this study.
Acknowledgments
The authors express sincere appreciation to all elderly participants for their invaluable time and effort, and to the research staff and laboratory assistants for their dedicated support throughout data collection and analysis.
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