Antonio’s Recommended Reading, Research, & Review for Human Performance - Issue #07 | June 2023

Every month, XSENSOR's Sports Performance Science Contributor, Antonio Robustelli, MSc, CSCS (Sports Performance Scientist & Technologist with OmniAthlete Performance Concept), will offer 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 critical takeaways, or read the complete studies at your own pace.

Research Title: A Prospective Study of the Muscle Strength and Reaction Time of the Quadriceps, Hamstring, and Gastrocnemius Muscles in Patients with Plantar Fasciitis

Authors: Lee JH, Jung HW, Jang WY

Journal: BMC Musculoskeletal Disorders

Publication Year: 2020

Abstract

Background: Muscle weakness is an important etiological factor in plantar fasciitis (PF), but available data on the role of the quadriceps, hamstring, and gastrocnemius (GCM) muscles are limited. This study compared the strength and reaction time of the quadriceps, hamstring, and GCM muscles and foot pressure between patients with PF and normal controls.

Methods: 21 PF patients and 21 normal controls were enrolled. Muscle strength was measured by the peak torque per body weight (Nmkg− 1 × 100). Muscle reaction time was evaluated by the acceleration time (AT, milliseconds). Foot pressure and posture were assessed by pedobarography [valgus/varus index (VV index), %].

Results: The strength of the quadriceps was significantly lower in the affected ankles of the PF group than in the control group (p = 0.005). The AT of the quadriceps and hamstring muscles was significantly increased in the affected ankles of the PF group than in the control group (quadriceps: p = 0.012, hamstring: p = 0.001), while the AT of the GCM muscle was significantly decreased (p = 0.009) and significantly correlated negatively with quadriceps muscle strength (r = −.598, p = 0.004) and AT (r = −.472, p = 0.031). Forefoot (p = 0.001) and hindfoot (p = 0.000) pressure were significantly greater, with the VV index showing hindfoot valgus in the affected ankles in the PF group compared to the control group (p = 0.039).

Conclusions: This study demonstrated weakness and delayed reaction time of the quadriceps and hamstring muscles, with a rapid reaction time of the GCM muscle in patients with PF.

Clinical Relevance: Clinicians and therapists should assess the function of the quadriceps and hamstring muscles when planning the management of PF patients without muscle tightness.

Why the Study Is Relevant

The study aims to analyze differences in strength and reaction time of the quadriceps, hamstring, and gastrocnemius muscles in individuals with diagnosed plantar fasciitis.

While the study aims to find an interesting causal relationship between foot pain and the function of the lower extremity muscles, the study's design has limitations. Unfortunately, the study is not done on athletes, there is no clear explanation of the exact measurement protocol for plantar pressure mapping data acquisition, and muscle strength of the hip muscles (i.e., gluteus muscles and hip abductors) has yet to be assessed.

Summary

Plantar fasciitis is a common problem associated with the onset of foot pain. Some causes have been identified in altered biomechanics, limited ankle dorsiflexion, and tightness of the hamstring muscles.

The study’s authors tried to investigate the role of muscle strength (quadriceps, hamstrings, and gastrocnemius) and plantar pressure values in individuals suffering from plantar fasciitis.

Key Takeaways

• Individuals with plantar fasciitis showed weakness and delayed reaction time of the quadriceps and hamstring muscles.
• Individuals with plantar fasciitis showed rapid reaction time in gastrocnemius muscles.
• Individuals with plantar fasciitis showed higher forefoot and rearfoot peak pressure values in the affected foot.

Read the full study.

Research Title: Effect of Stroke Direction on Plantar Pressure in Each Foot during the Forehand and Backhand Stroke among Healthy Adult Tennis Players of Different Performance Levels

Authors: Lambrich J, Muehlbauer T

Journal: BMC Sports Science, Medicine and Rehabilitation

Publication Year: 2023

Abstract

Background: In tennis, previous studies have shown differences in plantar pressure depending on tennis-specific movements (i.e., baseline play, serve & volley play, change of direction), playing surface (e.g., hard, grass, or clay), and serve type (e.g., slice, topspin, or flat). However, the influence of stroke direction on plantar pressure in tennis players with diverging skill levels is unknown. Thus, this study aimed to determine the effect of stroke direction on plantar pressure in each foot during the forehand and backhand stroke among players of different performance levels.

Methods: Thirty-nine healthy female and male adult tennis players (mean ± SD age: 23.5 ± 6.4 years) representing athletes from three performance levels (recreational, intermediate, advanced) participated in this study. The players performed longline/cross forehand and backhand groundstrokes (topspin) on a clay court while plantar pressure distribution was measured in each foot using flexible instrumented insoles.

Results: The three-way ANOVA (performance level × stroke direction × foot dominance) showed (A) no significant differences in plantar pressure data between cross and longline strokes in almost all cases, (B) in part, significantly larger pressure values in advanced compared to intermediate and recreational players, and (C) significantly larger pressure data for the dominant compared to the non-dominant foot in nearly all comparisons.

Conclusion: Regarding an appropriate plantar pressure distribution, our results suggest that during the training of primarily recreational and intermediate players, attention should be paid to the feet rather than to stroke direction.

Why the Study Is Relevant

The study aims to investigate the effect of stroke direction on plantar pressure distribution in both feet (dominant and non-dominant) during the forehand and backhand groundstroke.

The purpose of the study is to address an exciting topic to help coaches involved in tennis better understand specific training designs.

However, the design has a few limitations: the small sample size per group (N=13) and a pressure measurement device with wires and attachments on the lower leg may compromise the natural execution of sporting movements.

Summary

Stroke direction (cross and longline) associated with both stroke technique (forehand and backhand) and stroke type (slice and topspin) in tennis is a critical factor for variable groundstrokes during a game.

Several studies have tried to investigate the influence of different characteristics of a tennis serve and foot placement on plantar pressure distribution. However, there need to be more studies on the impact of stroke direction on plantar pressure distribution.

The authors of this study have tried to investigate how stroke direction influences plantar pressure distribution based on different players’ performance levels.

Key Takeaways

• Stroke direction does not influence plantar pressure.
• Performance level has a partial influence on plantar pressure.
• Foot dominance has the most influence on plantar pressure distribution.

Read the full study.

Research Title: Evaluating Footwear in the Wild: Examining Wrap and Lace Trail Shoe Closures during Trail Running

Authors: Honert EC, Harrison K, Feeney D

Journal: Frontiers in Sports and Active Living

Publication Year: 2023

Abstract

Trail running participation has grown over the last two decades. As a result, there have been an increasing number of studies examining the sport. Despite these increases, there needs to be more understanding regarding the effects of footwear on trail running biomechanics in ecologically valid conditions. This study evaluated how a Wrap vs. Lace closure (on identical shoes) impacts running biomechanics on a trail. Thirty subjects ran a trail loop in each shoe while wearing a global positioning system (GPS) watch, heart rate monitor, inertial measurement units (IMUs), and plantar pressure insoles. The Wrap closure reduced peak foot eversion velocity (measured via IMU), which has been associated with the fit. The Wrap closure also increased the heel contact area associated with the fit. This increase may be related to the subjective preference for the Wrap. Lastly, runners had a small but significant increase in running speed in the Wrap shoe with no differences in heart rate or subjective exertion. The Wrap closure fit better than the Lace closure on various terrain. This study demonstrates the feasibility of detecting meaningful biomechanical differences between footwear features in the wild using statistical tools and study design. Evaluating footwear in ecologically valid environments often creates additional variance in the data. This variance should not be treated as noise; instead, it is critical to capture this additional variance and challenges of ecologically valid terrain if we hope to use biomechanics to impact the development of new products.

Why the Study Is Relevant

The study evaluates how changing a trail shoe closure system impacts trail running biomechanics and performance.

The authors hypothesized that a wrap closure rather than a lace closure would provide:

• A reduced foot eversion velocity.
• Reduced loading rate.
• Reduced medial/lateral acceleration.
• Reduced peak pressure in toe and heel.
• Increased contact area in the toe and heel.

The study is the first to evaluate trail-specific footwear on terrain rather than in a lab-controlled environment, thus better translating to a real-world applied scenario.

Summary

Trail running is a sporting activity that has grown over the last two decades. Despite this increase in popularity and participation, the effects of footwear on trail running biomechanics in real-world conditions still need to be studied.

The authors of this study tried to address this problem by investigating the biomechanical outcomes of different footwear in an ecologically valid terrain.

Key Takeaways

• Wrap closure provides a better fit for trail running than lace closure.
• Wrap closure reduces peak foot eversion velocity, which is associated with a better fit.
• Wrap closure increases the heel contact area, which is associated with a better fit.

Read the full study.