Using statistical parametric mapping to assess the association of duty factor and step frequency on running kinetic

The Search for the Holy Grail in Running Biomechanics: Is There an Ideal Movement Profile for Minimizing Mechanical Overload?

BACKGROUND

Running biomechanics can influence injury risk, but whether the combined effect of different biomechanical factors can be identified by individual running profiles remains unclear. Here, we identified distinct biomechanical profiles among healthy runners, examined lower limb mechanical load characteristics, and evaluated potential implications for injury risk.

HYPOTHESIS

Multiple factors would serve as a common denominator allowing identification of specific patterns.

STUDY DESIGN

Cross-sectional.

LEVEL OF EVIDENCE

Level 2.

METHODS

Step cadence, stance time, vertical oscillation, duty factor, vertical stiffness, peak ground reaction force (GRF), and anteroposterior, lateral, and vertical smoothness were determined from 3-dimensional kinematic data from 79 healthy runners using a treadmill at 2.92 m/s. Principal component analysis, self-organizing maps, and K-means clustering techniques delineated distinct biomechanical running profiles. Mutual information analysis, Kruskal-Wallis, and Pearson's Chi-squared tests were conducted.

RESULTS

Five biomechanical profiles (P1-P5) demonstrated different running mechanical characteristics: P1 exhibited low cumulative and peak mechanical load due to a combination of high duty factor, low step cadence, and longer stance time; P2 showed characteristics associated with the lowest peak mechanical load due to reduced peak GRF and greater smoothness; P3 and P5 showed contrasting running patterns, but maintained moderate smoothness and peak GRF; and P4 exhibited the highest peak mechanical load, driven by high GRF, low duty factor, and high vertical oscillation.

CONCLUSION

The 5 profiles appear to be associated with different lower limb load patterns, highlighting previously unrecognized connections between biomechanical variables during running. Some variables contribute to increased peak and cumulative load, whereas others help reduce it, underscoring the complex interplay of biomechanical factors in running.

CLINICAL RELEVANCE

Identifying distinct running profiles can help clinicians better understand individual variations in mechanical load and injury risk, thus informing targeted interventions, such as personalized training adjustments or rehabilitation programs, to prevent injuries and enhance performance in runners.

Two types of insoles design to influence running biomechanics in opposite directions and individual responses

Introduction

Global running patterns vary along a spectrum defined by the degree of body verticality. This continuum ranges from extension (upright extended postures) to flexion (forward-leaning positions characterized by flexion at the hips and knees). Understanding these patterns is crucial for effective injury rehabilitation. Recent research has identified inefficiencies in vertical load management, leading to the development of extension- or flexion-based exercises. Insoles, while not typically designed for comprehensive extension or flexion adjustments, can complement these exercises. This study tested two novel insoles-extension and flexion-designed by a podiatrist based on principles such as higher shore values for enhanced extension increased thickness for greater flexion.

Methods

Eighteen recreational runners ran at 12 km/h on a treadmill under three conditions: no insole, extension insole, and flexion insole. We hypothesized that the extension insole would produce a lower duty factor (DF), greater vertical center of mass displacement (∆COM), and shorter time to maximum ankle pronation during ground contact (t max ⁡ .   pron ) with opposite effects expected for the flexion insole.

Results

However, the results did not support this hypothesis, as no significant effects of either insole were observed on DF, ∆COM, ort max ⁡ .   pron compared to running without an insole (p ≥ 0.38). Additionally, there was considerable variation in individual responses to the insoles. The extension insole resulted in a more extended running pattern in 50% of participants, while the flexion insole produced a more flexed pattern in 44% of participants. Notably, only 11% of participants reported both a more extended running pattern with the extension insole and a more flexed running pattern with the flexion insole.

Discussion

The anticipated effects of the insoles on running mechanics were not consistently observed, underscoring the complexity of insole interventions. This highlights the need for further research to improve insole design, refine insole prescription, and to better understand the nuances of running biomechanics.

Relation between soft tissue energy dissipation and leg stiffness in running at different step frequencies

This study aims to investigate the relationship between soft tissue energy dissipation and leg stiffness during running. Eight recreational healthy male runners (age: 22.2 ± 1.0 years; height: 1.84 ± 0.03 m; mass: 73.7 ± 5.7 kg) were asked to run at different speeds and step frequencies. Their soft tissue energy dissipation was estimated by the difference between the total mechanical work of the body, measured as the work done to move the body centre of mass relative to the surroundings plus the work to move the limbs relative to the body centre of mass, and lower-limb joint work. A mass-spring model with an actuator was used to analyse the force-length curve of the bouncing mechanism of running. In this way, the stiffness and damping coefficient were assessed at each speed and step frequency. Pearson's correlations were used to describe the relationship between the deviation from the spring-mass model and soft tissue energy fluctuations. The soft tissue dissipation was found to be significantly influenced by step frequency, with both positive and negative work phases decreasing when step frequency increases. Moreover, deviation from a spring-mass model was positively associated with the amount of soft tissue dissipation (r > 0.6). The findings emphasize the substantial role of soft tissues in dissipating or returning energy during running, behaving in a damped-elastic manner. Also, we introduce a novel approach for evaluating the elastic rebound of the body during running. The insights gained may have broad implications for assessing running mechanics, with potential applications in various contexts.

Mind to move: Differences in running biomechanics between sensing and intuition shod runners

Delving into the complexities of embodied cognition unveils the intertwined influence of mind, body, and environment. The connection of physical activity with cognition sparks a hypothesis linking motion and personality traits. Hence, this study explored whether personality traits could be linked to biomechanical variables characterizing running forms. To do so, 80 runners completed three randomized 50-m running-trials at 3.3, 4.2, and 5m/s during which their running biomechanics [ground contact time (tc), flight time (tf), duty factor (DF), step frequency (SF), leg stiffness (kleg), maximal vertical ground reaction force (Fmax), and maximal leg compression of the spring during stance (ΔL)] was evaluated. In addition, participants' personality traits were assessed through the Myers-Briggs Type Indicator (MBTI) test. The MBTI classifies personality traits into one of two possible categories along four axes: extraversion-introversion; sensing-intuition; thinking-feeling; and judging-perceiving. This exploratory study offers compelling evidence that personality traits, specifically sensing and intuition, are associated with distinct running biomechanics. Individuals classified as sensing demonstrated a more grounded running style characterized by prolonged tc, shorter tf, higher DF, and greater ΔL compared to intuition individuals (p≤0.02). Conversely, intuition runners exhibited a more dynamic and elastic running style with a shorter tc and higher kleg than their sensing counterparts (p≤0.02). Post-hoc tests revealed a significant difference in tc between intuition and sensing runners at all speeds (p≤0.02). According to the definition of each category provided by the MBTI, sensing individuals tend to focus on concrete facts and physical realities while intuition individuals emphasize abstract concepts and patterns of information. These results suggest that runners with sensing and intuition personality traits differ in their ability to use their lower limb structures as springs. Intuition runners appeared to rely more in the stretch-shortening cycle to energetically optimize their running style while sensing runners seemed to optimize running economy by promoting more forward progression than vertical oscillations. This study underscores the intriguing interplay between personality traits of individuals and their preferred movement patterns.