Antonio’s Recommended Reading, Research, & Review for Human Performance - Issue #13 | April 2025

XSENSOR's Sports Performance Science Contributor, Antonio Robustelli, MSc, CSCS (Sports Performance Scientist & Technologist with OmniAthlete Performance Concept), offers his take on essential and recommended reading, research, and review for plantar pressure applications using gait analysis for athletes.

Be sure to tune in to get the abstracts, summaries, and key takeaways, or read the complete studies.

Research Title: An Observational Study of Lower Limb Muscle Imbalance Assessment & Gait Analysis of Badminton Players

Authors: Huang P, Xu W, Bai Z, Yu L, Mei Q, Gu Y.

Journal: Frontiers in Bioengineering & Biotechnology

Publication Year: 2024

Abstract

Purpose: The imbalance of muscle strength indicators negatively impacts players. Lower limb muscle imbalance can cause gait abnormalities and increase the risk of muscle injury or decreased performance in significantly asymmetrical situations. This study assesses the lower limb muscle imbalance and gait feature between badminton players' dominant and non-dominant sides and the associations between the two variables.

Methods: The study included 15 badminton players with years of training experience. Muscle strength and gait parameters were obtained from isokinetic muscle strength testing and plantar pressure analysis systems. The symmetry index was calculated based on formulas such as plantar pressure distribution and percentage of plantar contact area.

Results: The isokinetic muscle strength test found significant differences in bilateral knee flexors' average power and total work at 60°/s angular speed. The hamstring to quadriceps ratio (H/Q) range of knee joints of the dominant and non-dominant sides is 0.63-0.74 at low speed, while the H/Q range is 0.81-0.88 at fast speed. The H/Q of bilateral knees increases with increasing angular velocity. As the angular velocity increases, the peak torque to body weight ratio (PT/BW) of the participants' bilateral knee flexors and extensors shows a decreasing trend. The asymmetry score of H/Q at 180°/s angular speed is positively related to step time and stance time. There are varying degrees of differences in gait staging parameters, plantar pressure in each area, plantar contact area, and symmetry index between badminton players' dominant and non-dominant sides when walking.

Conclusion: Badminton players have weaker flexors of the knee joint, imbalanced muscle strength in flexors and extensors, decreased lower limb stability, and risk of knee joint injury on the non-dominant side. The bending and stretching strength of the knee joint on the dominant side of the players is greater than that on the non-dominant side. The pressure in the first metatarsal region of the dominant side is higher, while that in the midfoot and heel regions is higher on the non-dominant side. Badminton players have better forward foot force and heel cushioning ability. Long-term badminton sports result in specialized changes in plantar pressure distribution and reduced symmetry.

Why the Study is Relevant

The study aims to evaluate the differences in lower limb muscle strength between the dominant and non-dominant sides and the differences between the flexor and extensor muscles in players who have engaged in long-term badminton training.

The study design is observational and involves a low sample size (n=15), which limits the statistical power and the overall significance of the results. There is no mention of the pre-participation screening performed on the athletes and how their physical condition, motor ability, and skill level were determined. The type of assessment performed, through isokinetic muscle testing and plantar pressure mat, probably has poor transfer to the dynamic real-time environment of sport, and assumptions on potential injury risk are challenging to make.

Summary

Badminton is a handheld racket sport that has been proven to cause upper-limb muscle imbalance. Lower-limb asymmetries due to lunge movements, sudden stops, and rapid direction changes may also lead to lower-limb injuries.

The authors of this study investigated whether the presence of muscle imbalances and lower limb asymmetries can inform training strategies to reduce the occurrence of injuries.

Key Takeaways

• College badminton players have weaker knee flexors on the non-dominant side.

• During walking, the first metatarsal bone experiences greater pressures.

Read the full study.

Research Title: The Influence of Pain Exacerbation on Rear-Foot Eversion & Plantar Pressure Symmetry in Women with Patellofemoral Pain: A Cross-Sectional Study

Authors: Yalfani A, Ahadi F, Ahmadi M.

Journal: BMC Musculoskeletal Disorders

Publication Year: 2025

Abstract

Background: The patellofemoral joint (PFJ) stress is a primary mechanical stimulus in patellofemoral pain (PFP) etiology and is affected by plantar pressure symmetry. This study evaluated how pain exacerbation affects the symmetry of rear-foot eversion and plantar pressure distribution.

Method: Sixty women with PFP participated in this study. Pain intensity, rear-foot eversion, and plantar pressure were evaluated in the two conditions with and without pain exacerbation during double-leg squats. The MANOVA test was used to compare the two conditions' pain intensity, rear-foot eversion, and plantar pressure symmetry. The Pearson correlation was used to evaluate the relationship between the pain intensity with the rear-foot eversion and the plantar pressure symmetry.

Results: The comparison between the two conditions showed a significant difference in pain intensity (P < 0.001, η2 = 0.623), rear-foot eversion (P < 0.001, η2 = 0.485), plantar pressure distribution symmetry of the right-left foot (P < 0.001, η2 = 0.438), forefoot and rear-foot of the right foot (P < 0.001, η2 = 0.607), and forefoot and rear-foot of the left foot (P < 0.001, η2 = 0.548). An excellent correlation was observed between the pain intensity with rear-foot eversion (P < 0.001, r = 0.835) and plantar pressure distribution symmetry of the right-left foot (P < 0.001, r = 0.812), forefoot and rear-foot of the right foot (P < 0.001, r = 0.834), and forefoot and rear-foot of the left foot (P < 0.001, r = 0.811).

Conclusions: After the pain exacerbation, the rear-foot eversion was greater, and plantar pressure asymmetrical was observed, which can help in the development of PFP severity.

Why the Study is Relevant

The study aims to evaluate the influence of pain exacerbation on rear-foot eversion and plantar pressure symmetry in women with PFP. The authors hypothesized that 1) after pain exacerbation, rear-foot eversion would be greater and 2) the plantar pressure distribution would be asymmetric.

The cross-sectional study design involves an acceptable sample size (n=60). The protocol used and the type of hardware employed to measure plantar pressure were properly described.

The research question can provide a fascinating insight into the relationship between pain intensity and parameters such as rear-foot eversion and plantar pressure distribution symmetry.

Summary

PFP is a clinical condition with an estimated prevalence of about 13% in women 18-35 years old. Women are 2.23 times more susceptible to PFP than men. Rear-foot eversion is an intrinsic risk factor for increased PFJ stress and PFP.

Recent studies have shown that pain intensity has the potential to influence kinematic and kinetic variables. In other words, during biomechanical analyses and clinical evaluations, different levels of pain in women with PFP can show distinct mechanical strategies.

The authors of this study tried to evaluate the effects of pain exacerbation on rear-foot eversion and plantar pressure symmetry in patients with PFP.

Key Takeaways

• After the pain exacerbation, the rear-foot eversion was greater.

• Asymmetrical plantar pressure was observed in the forefoot and left foot (asymptomatic limb).

Read the full study.

Research Title: Task-Specific Differences in Lower Limb Biomechanics During Dynamic Movements Individuals with Chronic Ankle Instability Compared with Controls

Authors: Altun A, Dixon S, Rice H.

Journal: Gait & Posture

Publication Year: 2024

Abstract

Background: Chronic ankle instability (CAI) has been associated with lower limb deficits that can lead to altered biomechanics during dynamic tasks. To date, contradictory findings in terms of ankle and hip joint biomechanics have been influenced by the variety of movement tasks and varying definitions of the CAI condition.

Research question: How do biomechanical variables of the lower extremities differ during walking, running, and jump-landing in individuals with CAI compared with those without CAI?

Methods: Thirty-two individuals (17 CAI and 15 controls) participated in this retrospective case-control study. During the tasks, sagittal and frontal plane ankle and hip joint angles and moments and mediolateral foot balance (MLFB) were calculated. Statistical parametric mapping (SPM) was used to analyze the whole trajectory and detect group differences. Discrete variables, including initial contact (IC) and peak angles and moments, were additionally compared.

Results: No differences were found between groups during walking. During running, the CAI group exhibited a lower plantar flexor moment (p < 0.001) and more laterally deviated MLFB (p = 0.014) during mid-stance when compared to controls. Additionally, participants with CAI had a significantly greater peak plantar flexion angle in early stance (p = 0.022) and a reduced peak plantar flexor moment (p = 0.002). In the jump-landing, the CAI group demonstrated an increased hip extensor moment (p = 0.008) and a greater peak hip adduction angle (p = 0.039) shortly after ground contact compared to the control group.

Significance: Differences in ankle and hip biomechanics were observed between groups during running and jump landing but not during walking. These differences may indicate impairments in the sensorimotor system or learned strategies adopted to minimize instability and injury risk, and they can help inform future intervention design.

Why the Study is Relevant

The study aims to identify differences in joint kinematics, joint kinetics, and plantar pressure distribution between CAI and healthy individuals during walking, running, and jump-landing. The study design is retrospective case-control and involves a low sample size (17 CAI and 15 control). The measurement protocol and equipment used were standardized and described very well. The research question tried to address the issue of biomechanical behavior and plantar pressure distribution patterns in individuals suffering from CAI.

Summary

Ankle sprains are among the most common musculoskeletal injuries. Approximately 23,000 and 5,000 ankle injuries occur daily in the USA and UK, respectively. A recurrence rate of up to 73% has been reported, and about 74% of individuals with a history of lateral ankle instability (LAS) develop residual symptoms such as pain, swelling, weakness, and instability. These recurrent injuries and residual symptoms are chronic ankle instability's main CAI characteristics.

To better understand the underlying mechanisms of CAI, the authors of this study tried to identify differences in plantar pressure distribution and lower limb biomechanics between CAI and healthy individuals.

Key Takeaways

• Differences in ankle and hip biomechanics were observed between individuals with CAI and a control group during running and jump landing but not during walking.

• Individuals with CAI demonstrated lower plantar flexor moments, a more laterally deviated mediolateral foot balance, and greater peak plantar flexion angle during running than control participants.

Read the full study.