Clear decreases in horizontal force production capacity during sprint acceleration have been reported after hamstring injuries (HI) in football players. We hypothesized that lower F_H0 is associated with a higher HI occurrence in football players. We aimed to analyze the association between sprint running horizontal force production capacities at low (F_H0) and high (V₀) velocities, and HI occurrence in football. This prospective cohort study included 284 football players over one season. All players performed 30 m field sprints at the beginning and different times during the season. Sprint velocity data were used to compute sprint mechanical properties. Players’ injury data were prospectively collected during the entire season. Cox regression analyses were performed using new HI as the outcome, and horizontal force production capacity (F_H0 and V₀) was used at the start of the season (model 1) and at each measurement time point within the season (model 2) as explanatory variables, adjusted for individual players’ (model 2) age, geographical group of players, height, body mass, and previous HI, with cumulative hours of football practice as the time scale. A total of 47 new HI (20% of all injuries) were observed in 38 out of 284 players (13%). There were no associations between F_H0 and/or V₀ values at the start of the season and new HI occurrence during the season (model 1). During the season, a total of 801 measurements were performed, from one to six per player. Lower measured F_H0 values were significantly associated with a higher risk of sustaining HI within the weeks following sprint measurement (HR = 2.67 (95% CI: 1.51 to 4.73), p < 0.001) (model 2). In conclusion, low horizontal force production capacities at low velocity during early sprint acceleration (F_H0) may be considered as a potential additional factor associated with HI risk in a comprehensive, multifactorial, and individualized approach.

This study investigated the effects of shoe drop on lower limb kinematics and kinetics in female runners.Fifteen healthy female runners ran on a 15‐m runway at their preferred speed with three different shoe‐drop conditions: 0 (D₀), 6 (D₆) and 10 (D₁₀) mm. Three‐dimensional marker positions and ground reaction forces were recorded to analyse kinetic and kinematic parameters using zero‐ (0D) and one‐dimensional (1D) metrics (statistical parametric mapping, SPM). Regarding 0D parameters, significantly higher loading rates and transient peaks were found in D₀ compared to D₆ and D₁₀ conditions (both p < .01). For 1D analysis, significantly higher ankle dorsiflexion moments were found in D₀ compared to D₆ and D₁₀ during the braking phase (p < .01). Lower knee extension moments between 52% and 55% and 61% and 65% of contact time (p < .05) were also found. No difference was found between D₆ and D₁₀ conditions (p > .05). As previously shown in men, this study demonstrates that shoe drop influences running kinematic and kinetic patterns. Using SPM analysis in conjunction with classical analysis, the study adds new understanding on the influence of shoes on joint moment during contact time.

During running, the human body is subjected to impacts generating repetitive soft tissue vibrations (STV). They have been frequently discussed to be harmful for the musculoskeletal system and may alter running gait. The aims of this narrative review were to: (1) provide a comprehensive overview of the literature on STV during running, especially why and how STV occurs; (2) present the various approaches and output parameters used for quantifying STV with their strengths and limitations; (3) summarise the factors that affect STV. A wide set of parameters are employed in the literature to characterise STV. Amplitude of STV used to quantify the mechanical stress should be completed by time–frequency approaches to better characterise neuromuscular adaptations. Regarding sports gear, compression apparels seem to be effective in reducing STV. In contrast, the effects of footwear are heterogeneous and responses to footwear interventions are highly individual. The creation of functional groups has recently been suggested as a promising way to better adapt the characteristics of the shoes to the runners’ anthropometrics. Finally, fatigue was found to increase vibration amplitude but should be investigated for prolonged running exercises and completed by an evaluation of neuromuscular fatigue. Future research needs to examine the individual responses, particularly in fatigued conditions, in order to better characterise neuromuscular adaptations to STV.

Establishing a sprint acceleration force–velocity profile is a way to assess an athlete’s sprint-specific strength and speed production capacities. It can be determined in field condition using GNSS-based (global navigation satellite system) devices. The aims of this study were to (1) assess the inter-unit and the inter-trial reliability of the force–velocity profile variables obtained with K-AI Wearable Tech devices (50 Hz), (2) assess the concurrent validity of the input variables (maximal sprint speed and acceleration time constant), and (3) assess the validity of the output variables (maximal force output, running velocity and power). Twelve subjects, including one girl, performed forty-one 30 m sprints in total, during which the running speed was measured using two GPS (global positioning system) devices placed on the upper back and a radar (Stalker^® Pro II Sports Radar Gun). Concurrent validity, inter-device and inter-trial reliability analyses were carried out for the input and output variables. Very strong to poor correlation (0.99 to 0.38) was observed for the different variables between the GPS and radar devices, with typical errors ranging from small to large (all < 7.6%). Inter-unit reliability was excellent to moderate depending on the variable (ICC values between 0.65 and 0.99). Finally, for the inter-trial reliability, the coefficients of variation were low to very low (all < 5.6%) for the radar and the GPS. The K-AI Wearable Tech used in this study is a concurrently valid and reliable alternative to radar for assessing a sprint acceleration force–velocity profile.

Sprint running is a critical performance parameter in many sports such as athletics, soccer or rugby that implies large forward acceleration. From a mechanical standpoint, previous studies showed t...

The aim of this study was to investigate if acute impairments of the footwear midsole materials could interact with the modifications of the running patterns after a fatiguing trail running race. We hypothesized that introducing a control pair of shoes after the race, would modify running mechanics by partially correcting the alterations generated by the deteriorated properties of the shoes worn during the race. Eighteen participants ran on a treadmill at 10 km·h⁻¹ pre- and post-race in three conditions varying the step frequency (free or fixed) or the footwear (control or personal shoes). Spatiotemporal parameters, tibial accelerations across the running conditions and shoe mechanical properties were measured. Significant changes in shoe characteristics (i.e. reduced thickness and increased stiffness) were measured after the race in the personal footwear. At free step frequency, significant changes in contact (+1.3 ± 3.5%) and flight (−19.4 ± 23.7%) times, step frequency (+2.9 ± 2.9%) and peak-to-peak amplitude acceleration at the tibia level (−3.6 ± 18%) were found. The peak-to-peak amplitude of the mediolateral axis showed a significant shoe × time interaction meaning that the control footwear could have had an impact in the running pattern. However, contrary to our hypothesis, no interaction effects were found between the changes in footwear and the changes in spatiotemporal parameters. In conclusion, impairments of shoes characteristics affect impact but not running mechanics.