Ground Contact Time Research Articles

Joint mechanical characteristics of vertical jumping in elite sprinters

This study aims to investigate the key lower limb joint biomechanical factors affecting the performance of vertical jumping in high-level sprinters, focusing on analysing the torque, power output and stiffness of the hip, knee and ankle joints during the vertical jumping process. The relationship between the joint biomechanical parameters and the key indexes of vertical jump performance, including ground contact time, free height and reaction power index, was systematically analysed through the simultaneous acquisition of 3D kinematic and kinetic data of the sprinters. The results showed that different lower limb joints play key roles in different phases of the long jump. During the centrifugal phase (landing), knee stiffness had a significant effect on ground contact time, with athletes with greater stiffness demonstrating shorter contact times, thus contributing to a quicker entry into the centripetal phase (jumping). In contrast, during the centripetal phase, ankle power output was highly correlated with free height and explosive performance, showing the decisive role of the ankle joint in vertical mobility at the start of the jump. The hip joint also plays a role in coordinating upper and lower limb movements and enhancing power transfer throughout the exercise process, but its influence is more indirect. This study provides biomechanical empirical evidence for the training of sprinters, especially by enhancing knee joint stiffness and ankle joint power output, athletes can effectively improve the performance of vertical jump manoeuvres. These findings provide a scientific basis for coaches and athletes to optimise their training programmes and improve their performance in competitions, and provide a reference direction for future related research.

The Ability of Stryd Footpod Metrics to Reflect Changes in Metabolic Power Between Running Shoe Types

ABSTRACT It is unclear if running power (RP) estimated by the Stryd footpod device maintains its linear relationship to metabolic power (WMET) when switching between training and racing shoe types. This study determined if RP estimated by the Stryd footpod and its other spatiotemporal metrics reflect the improvement (decrease) in WMET when wearing high-performance racing shoes (HPRS; Nike AlphaFly Next%) compared to control training shoes (CTS; Nike Revolution 5). Fourteen well-trained runners completed two treadmill tests: Absolute Velocity Running Test (AVRT; 11.3–14.5 km·hr−1) and Relative Velocity Running Test (RVRT; 55–75% VO2MAX). WMET was determined with indirect calorimetry. RP was not significantly different between shoe types (p > 0.432) during the AVRT, but WMET was ~5% lower in HPRS (p < 0.001). During the RVRT, participants ran ~6% faster and at ~6% higher RP (both, p < 0.001) in HPRS for the same WMET (p = 0.869). Linear mixed models confirmed WMET was ~5% lower in HPRS for a given RP (p < 0.001). Still, RP and WMET were strongly related within shoe types (p < 0.001, conditional-R 2 = 0.982, SEE = 2.57%). Form power ratio and ground contact time correlated with energetic cost (p < 0.011) but did not fully reflect the influence of shoe type. Therefore, runners should account for their shoe type when using RP to indicate WMET between training and racing.

Morphological and Performance Biomechanics Profiles of Draft Preparation American-Style Football Players

Background/Objectives: Using advanced methodologies may enhance athlete profiling. This study profiled morphological and laboratory-derived performance biomechanics by position of American-style football players training for the draft. Methods: Fifty-five players were categorized into three groups: Big (e.g., lineman; n = 17), Big–skill (e.g., tight end; n = 11), and Skill (e.g., receiver; n = 27). Body fat (BF%), lean body mass (LBM), and total body mass were measured using a bioelectrical impedance device. Running ground reaction force (GRF) and ground contact time (GCT) were obtained using an instrumented treadmill synchronized with a motion capture system. Dual uniaxial force plates captured countermovement jump height (CMJ-JH), normalized peak power (CMJ-NPP), and reactive strength. Asymmetry was calculated for running force, GCT, and CMJ eccentric and concentric impulse (IMP). MANOVA determined between-group differences, and radar plots for morphological and performance characteristics were created using Z-scores. Results: There was a between-group difference (F(26,80) = 5.70, p &lt; 0.001; Wilk’s Λ = 0.123, partial η2 = 0.649). Fisher’s least squares difference post hoc analyses showed that participants in the Skill group had greater JH, CMJ-NPP, reactive strength, and running GRF values versus Big players but not Big–skill players (p &lt; 0.05). Big athletes had greater BF%, LBM, total body mass, and GCT values than Skill and Big–skill athletes (p &lt; 0.05). Big–skill players had greater GCT asymmetry than Skill and Big players (p &lt; 0.05). Asymmetries in running forces, CMJ eccentric, and concentric IMP were not different (p &gt; 0.05). Morphological and performance biomechanics differences are pronounced between Skill and Big players. Big–skill players possess characteristics from both groups. Laboratory-derived metrics offer precise values of running and jumping force strategies and body composition that can aid sports science researchers and practitioners in refining draft trainee profiles.

Spatiotemporal kinematics during top speed sprinting in male intercollegiate track and field and team sport athletes

ABSTRACT We investigated spatiotemporal kinematics during top speed sprinting and biomechanical running strategies in 98 male intercollegiate athletes from a range of athletic backgrounds in track and field (TF, n = 28) and team sports (TS, n = 70). Participants completed 40 m running trials with sagittal plane motion analyses of high-speed video captured from 30 m to 40 m. Across the entire sample, measures of contact time, step rate, step length, flight length and duty factor (ratio of contact duration to stride duration) were meaningfully correlated with top speed (p < 0.05, 0.51 ≤ |r or ρ| ≤ 0.78). Flight time and contact length were weakly correlated with top speed (p < 0.05, 0.27 ≤ |r or ρ| ≤ 0.34). When comparing sub-groups of Slow TF (n = 14) and Fast TS athletes (n = 22) with similar top speeds (~9.3 m/s), Fast TS athletes clearly demonstrated a more ground-based strategy, with longer ground contact times and contact lengths, shorter flight times and flight lengths, and larger duty factors. Therefore, the results of this study suggest that existing technical models and normative metrics based on data from TF athletes could require modification when evaluating and coaching sprinting performance with TS athletes.

Association Between Reactive Strength Index During Single-Limb Vertical Continuous Jumps and Isokinetic Knee Extensor Strength Following Anterior Cruciate Ligament Reconstruction

OBJECTIVE: To analyze the association between asymmetry in the reactive strength index (RSI) during single-limb vertical continuous jumps (SVCJs) and isokinetic knee extensor strength in athletes who have undergone anterior cruciate ligament reconstruction (ACLR) DESIGN: Cross-sectional study METHODS: This study included 75 athletes (40 female athletes) aged 23.7±8.6 years who had undergone ACLR (mean time from ACLR to measurement: 8.8±4.1 months). The ground contact time and flight time during SVCJs were measured using a force plate, and jump height was calculated from the flight time. The RSI during SVCJs was calculated as follows: RSI = jump height (cm)/contact time (s). The knee extensor strength was measured using an isokinetic dynamometer at 60°/s. The limb symmetry index (LSI) of RSI during SVCJs and knee extensor strength were calculated by dividing the values of the involved and uninvolved limbs. Age, sex, modified Tegner activity scale, and subjective knee function were also recorded. Univariable and multiple regression models were used to assess the association between these and the knee extensor strength. RESULTS: The involved limb showed significantly lower isokinetic knee extensor strength ( P&lt;0.001, effect size=0.55) and RSI during SVCJs ( P&lt;0.001, effect size=0.70) than did the uninvolved limb. In the multiple regression model, only LSI of RSI during SVCJs remained significant (B=0.440, SE=0.068, β=0.604) and accounted for 36.4% of the variance in knee extensor strength recovery ( P&lt;0.001, r2=0.364). CONCLUSION: RSI asymmetry during SVCJs was strongly associated with isokinetic knee extensor strength asymmetry.

Validity and reliability of running gait measurement with the ViMove2 system.

Running biomechanics have traditionally been analysed in laboratory settings, but this may not reflect natural running gait. Wearable technology has the potential to enable precise monitoring of running gait beyond the laboratory. This study aimed to evaluate the analytical validity and intra-session reliability of temporal running gait outcomes measured by the ViMove2 wearable system in healthy adults. Seventy-four healthy adults (43 males, 31 females, aged 18-55 years) wore the inertial device, ViMove2 on the tibia. Participants ran on a treadmill for one minute at various speeds (8, 10, 12, 14km/hr), completed in a standardised shoe (Saucony Guide Runner). Running gait was measured with the ViMove2 wearable and 3D motion capture (Vicon). Temporal running gait outcomes included ground contact time (GCT) and cadence (steps/min). GCT and cadence from the ViMove2 had face validity with expected changes in outcome with different running speeds, but ViMove2 tended to over-estimate GCT, and under-estimate cadence compared to the reference, especially at slower speeds. GCT demonstrated moderate to good agreement to the reference at speeds >10km/hr, but poor agreement at 8km/hr and within female runners. Cadence had moderate to excellent agreement across speeds compared to the reference. GCT and cadence had excellent reliability across speeds, but at 8km/hr GCT had good agreement between trials. Overall, temporal gait outcomes of GCT and cadence can be measured with the ViMove2, but accuracy and reliability are impacted at slow running speeds and within female runners. Future work is needed to clarify sex or speed-dependent corrections to algorithms / outcomes to aid interpretation and application.

The Effects of Carbon Insoles on Vertical Leg Stiffness and Reactive Strength as Indicators of Sprint Performance

Background: Sprinting is the peak expression of running performance and different strength and physical characteristics play roles in the expression of sprint speed. Leg stiffness and reactive strength index (RSI), which measures the strength of stretch-shortening cycle, are two major factors on rate of force development and performance. It is well known that carbon fiber insoles optimize energy return while minimizing energy loss. Objectives: The purpose of this study was: (1) to investigate the effects of a carbon fiber insole on the expression of vertical leg stiffness (kvert) and RSI during 20-yard sprint and drop jump; and (2) to examine the effects of the carbon insoles on sprint kinetics and kinematics. Methods: Using a randomized crossover design, fifteen participants performed a drop jump and a 20-yard sprint in two shoe conditions (carbon, traditional insoles) to measure RSI, Kvert, peak vGRF, ground contact time (GCT), speed, knee angle at contact, and knee angle at toe-off. Results: Significant differences between conditions for the performance variables occurred only in the drop jump (kvert, p = 0.023; peak vGRF, p = 0.001). Conclusions: Further research is needed to examine sprint kinetics and kinematics with varying insole stiffness at maximal velocity.

Gait performance changes after ten cervical retractions

Background and Study Aim. Students are prone to spine overloading, as they often spend prolonged periods in unfavorable postures. They tend to struggle with balancing study time and leisure physical activity. The head and neck regions are particularly rich in proprioceptors. Prolonged forward head posture (protraction) can lead to balance disturbances. This, in turn, affects gait and overall body posture. The aim of this study was to examine the effects of a series of corrective active head exercises on gait, a fundamental form of movement, in a group of healthy university students. Material and Methods. Gait patterns were assessed in 10 healthy male full-time students with an average age of 22.8 years (SD = 1.1). The assessment was based on the regional distribution of plantar pressure across two measurement sessions. One session was conducted before, and one after performing 10 active head retractions. Gait changes were analyzed in ten foot regions for 200 steps of each participant. Results. After 10 cervical retractions, a decrease in pressure, ground reaction force, contact time, and area values was observed in the 1st metatarsal head (1MTH). Conversely, an increase in these quantities was found in the toes. Additionally, there was a tendency toward a decrease in the contact area of the heel and 3rd metatarsal head (3MTH), along with increased contact time in the midfoot. Performing 10 neck retractions altered gait by inducing heel supination. It also increased hallux involvement in propulsion and widened the base of toe support. Conclusions. Even a few movements that correct head protraction have an immediate effect on whole-body movement. This effect suggests potential benefits of incorporating neck retractions into physical education programs for students. Even when time-consuming forms of regular exercise are not feasible, performing just a few neck-correcting movements can positively impact overall body movement.

Influence of the Beiring Sorenson Hold and the Barbell Back Squat on Running Cadence in Military Ruck Marching: A Cross-Sectional Observational Study

Ruck marching is a key performance indicator for tactical preparation; however, marching under load causes changes in biomechanics, which can increase injury risk. Although this risk of injury from changes is known, current methods commonly used for assessing physical fitness have not adequately identified how to minimize these changes. In this observational study, 14 ROTC cadets underwent a series of physical muscular fitness tests prior to performing a six-mile ruck march. These included an evaluation of postural endurance via the Biering Sorenson hold, lower body strength via the back squat, and upper body strength via bench press. After the tests were performed, ruck march performance was evaluated by total time to completion and running dynamics. Multiple regression analysis was performed to determine if bench press maximum, back squat maximum, or Sorenson hold were predictors of the performance of the ruck March. Average cadence shared a positive significant relationship with the Sorenson hold (r = 0.76, p = 0.02) and a negative significant relationship with the back squat (r = -0.76, p = 0.02). Additionally, the Sorenson hold did not share any significant relationships with total ruck time (r = -0.3, p = 0.29) or ground contact time (r = -0.41, p = 0.31). The back squat did not share significant relationships with ground contact time (r = -0.37, p = 0.37) or average smoothness (r = -0.38, p = 0.31). This study highlights the potential relationship that the Sorenson hold and back squat can have on running cadence, which has shown significant changes in previous research evaluating the changes in running performance and characteristics from weight ruck marching. Further investigation of the relationship of these assessments on the performance of ruck marching should be performed with larger numbers of cadets in the future.

An arm swing enhances the proximal-to-distal delay in joint extension during a countermovement jump

An abundance of degrees of freedom (DOF) exist when executing a countermovement jump (CMJ). This research aims to simplify the understanding of this complex system by comparing jump performance and independent functional DOF (fDOF) present in CMJs without (CMJNoArms) and with (CMJArms) an arm swing. Principal component analysis was used on 39 muscle forces and 15 3-dimensional joint contact forces obtained from kinematic and kinetic data, analyzed in FreeBody (a segment-based musculoskeletal model). Jump performance was greater in CMJArms with the increased ground contact time resulting in higher external (p = 0.012), hip (p < 0.001) and ankle (p = 0.009) vertical impulses, and slower hip extension enhancing the proximal-to-distal joint extension strategy. This allowed the hip muscles to generate higher forces and greater time-normalized hip vertical impulse (p = 0.006). Three fDOF were found for the muscle forces and 3-dimensional joint contact forces during CMJNoArms, while four fDOF were present for CMJArms. This suggests that the underlying anatomy provides mechanical constraints during a CMJ, reducing the demand on the control system. The additional fDOF present in CMJArms suggests that the arms are not mechanically coupled with the lower extremity, resulting in additional variation within individual motor strategies.

Effects of Fatigue on Lower Limb Biomechanics and Kinetic Stabilization During the Tuck-Jump Assessment.

General and local muscular fatigue is postulated to negatively alter lower limb biomechanics; however, few prospective studies have been done to examine the effect of fatigue on tuck-jump performance. The tuck-jump assessment (TJA) is a criteria-based visual screening tool designed to identify neuromuscular deficits associated with anterior cruciate ligament (ACL) injury. Use of kinetics during the TJA after an intense sport-specific fatigue protocol may identify fatigue-induced neuromuscular deficits associated with ACL injury risk. To examine the effects of a sport-specific fatigue protocol on visually evidenced (2-dimensional) technical performance of repeated tuck jumps and lower limb kinetic stabilization. Cross-sectional study. Laboratory. Twelve female netball athletes (age = 20.8 ± 2.6 years, height = 170.0 ± 0.04 cm, mass = 67.5 ± 7.4 kg). Participants performed 1 set of a TJA before and after a sport-specific fatigue protocol. Paired t tests and effect sizes were used to evaluate differences and the magnitude of differences in TJA scoring criterion, kinetics, and kinetic stabilization prefatigue to postfatigue. A small increase was observed for vertical relative lower extremity stiffness postfatigue (P = .005; Hedges g = 0.45). Peak center-of-mass displacement, time of jump cycle, ground contact time, flight time, jump height, and vertical net impulse decreased with small to moderate effect sizes (P < .01; Hedges g range, 0.41-0.74). No differences were observed for TJA composite scores, peak vertical ground reaction force, and stabilization indices of kinetic variables after the fatigue protocol (P > .05). Kinetic analysis of repeated tuck jumps after a fatigue protocol identified an altered jumping strategy, which was not identifiable via visual 2-dimensional assessment. However, based on kinetic measures, fatigue induces a stiffer jumping strategy, and practitioners should consider assessing load attenuation strategies that may not be visually evident when evaluating ACL-injury risk factors in athletes who are fatigued.

Associations between running mechanics, functional lower extremity strength, and stress urinary incontinence in parous female runners.

Women with stress urinary incontinence (SUI) may have altered running mechanics and reduced hip muscle strength compared to women without SUI. Little research has examined running metrics and functional lower extremity strength of parous runners. To determine if stress urinary incontinence (SUI) severity correlates with running metrics and lower extremity muscle strength among parous women. Cross-sectional observational study of 22 parous participants (mean age 39.8 years, with a mean of 3.4 pregnancies and 8.1 years interval since last delivery). Participants completed the International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form (ICIQ-UI), Urinary Distress Inventory (UDI) 6, Colorectal-Anal Distress (CRAD) Inventory 8, and Pelvic Organ Prolapse Distress Inventory (POPDI) 6, Questionnaire for Urinary Incontinence Diagnosis (QUID), and provided demographic, relevant running, and obstetric/gynecologic history information. After a brief warm-up, participants completed 30-second single leg sit to stand tests bilaterally and a standardized 10-minute treadmill run with pod cadence assessment. Pearson-product moment correlation coefficients were calculated (alpha = 0.05). Prolonged ground contact times were associated with higher ICIQ-UI SF (r = 0.523, p = 0.015), POPDI-6 (r = 0.694, p < 0.001), and UDI-6 scores (r = 0.577, p = 0.006), while lower cadences were associated with higher POPDI-6 (r = -0.550, p = 0.010) and UDI-6 scores (r = -0.444, p=0.044). Parous female runners with more severe SUI and prolapse symptoms demonstrate altered running mechanics characterized by prolonged ground contact times and slower cadences.

Do lower limb kinetic and kinematic differences in drop jump landings persist when players have returned to sport following knee ligamentous injuries?

Knee injuries (KI) are identified as one of the most burdensome lower limb injuries in football with long and complicated rehabilitation and high re-injury risk. Current research often describes technique deficits being present upon RTS, often being a result of poor return to sport (RTS) testing procedures. More recently, research has advocated the use of single leg vertical jump assessments, due to the specificity of the movement to injury mechanisms and the ability to consider different phases of the task to inform practitioners of joint contributions to the propulsion and landing phases. The aim of this research is to identify whether these functional deficits exist 12-24 months post RTS authorisation, to help inform future RTS in applied practice. Twenty-four semi-professional male footballers (mean ± SD: age 25 ± 4 years; stature 182 ± 7 cm; body mass 80 ± 8 kg) were recruited into a previously injured and a control group. Participants completed 5 repetitions of single leg drop jump (SLDJ). Jump height, ground contact time, reactive strength index, peak moments, angles and power contributions for the hip, knee and ankle were measured using Qualisys Track Manager then exported to Visual 3D. This study was approved by the Edge Hill University Ethics Committee. No significant findings were identified for landing one however, during the propulsion phase there was a difference between groups (P = 0.026, d=1.14) for knee flexion at take-off. Most differences were identified during landing two bilaterally in both groups. Within the injured group, differences were identified for peak hip (P = 0.011, d = 0.028) and knee powers (P &lt; 0.001, d = 1.269), hip (P &lt; 0.001, d = 1.924) and knee power contribution % (P &lt; 0.001, d = 1.269). No differences were identified for the performance measures or through performing statistical parametric mapping for hip and knee powers for all three phases. Joint coupling analysis was conducted for the total ground contact time amalgamating the landing and propulsion phase, this was analysed as Hip-Knee, Hip-Ankle and Knee-Ankle, with significant findings in Hip-Knee and Hip-ankle. Both groups elicited bilateral differences however, no differences between the injured limb and dominant control limb were identified. To better apply this form of analysis to RTS testing, functional movements such should be undertaken when athletes are injury free to provide baseline measurements to refer to if undertaking rehabilitation from KI. Likewise, the current study identified that joint contributions could be identified in a more applied setting using the range of motion data from each joint.

An investigation on sex-based disparities in male and female collegiate athlete reactive strength index

Reactive strength is the ability to effectively use a fast stretch shortening cycle (SSC) with the eccentric into a concentric contraction (Rebelo et al., 2022, Healthcare, 10, 593). A fast SSC is determined to be &lt;200 ms due to a preliminary study by (Schmidtbleicher &amp; Komi, 1992, Encyclopedia Sports Med. Vol. 3 Strength and Power in Sport) reviewing muscular contractions. Reactive strength is determined through two different metrics used within the literature which are ground contact time (GCT) and jump height (JH) allowing for understanding on how an athlete can utilise the myotatic reflex to react with the floor. Reactive Strength Index (RSI) is typically measured via drop jump (DJ) and 10/5 reactive pogo jumps. A novel way to measure RSI is via a rebound countermovement jump (RCMJ) which utilises RSI-Modified and includes time to take off instead of ground contact time. RSI is an important metric to measure because it has implications within sport-specific metrics like sprinting and jumping (Jarvis et al., 2022, Sports Med, 52, 301-330). However, some of the limitations of RSI are it is a ratio metric, and therefore RSI can mask underpinning metrics. As a result, additional metrics such as such a force, velocity and power can help better understand athlete development and the underpinning key performance indicators. However, many metrics within reactive jumps remain unsearched. Data will be collected from around 16 university athletes aged 18-25 currently competing in sport with at least one year’s experience in resistance training. Data will be collected using Hawkins dynamic force plates, sampling at 1000 Hz, and has recently been reported to be valid and reliable (Badby et al., 2023, Sports, 23, 4820) Participants will be asked to complete 3 DJ, RCMJ and 10/5 jump trials on two separate occasions separated by a minimum of 48 hours. Athletes will be instructed to perform a quiet standing period for 1 second before and after each jump to calculate body weight by the 5 × standard deviation method. Therefore, the study aims to compare the disparities between all three jumps aswell, sexes and the potential implications on performance. Previous studies displayed significant disparities between male and female participants. Therefore, the null hypothesis for this study is to display a non-significant difference across sexes aswell as between jumps. A limitation to this study is controlling the standardisation of variables such as squat depth during all tests.

Stability of Running Stride Biomechanical Parameters during Half-Marathon Race

This study explores the stability of biomechanical parameters of the running stride of male trained athletes during a half-marathon competition. Using a field-based descriptive design, eight male athletes from a local training group were monitored throughout an official half-marathon race under identical conditions, assessing biomechanical parameters including ground contact time (GCT), leg spring stiffness (LSS), vertical oscillation (VO), and stride length (SL) recorded via the Stryd Summit Power Meter. A repeated measures analysis of variance (RM ANOVA) was conducted to detect significant changes in biomechanical parameters as the race progressed. Results demonstrated minimal changes in all parameters, with no significant differences observed for GCT (F = 0.96, p = 0.38), VO (F = 0.23, p = 0.87), and SL (F = 1.07, p = 0.35), and a small (η2 = 0.004) yet statistically significant difference in LSS (F = 5.52, p = 0.03) between the first and second segments, indicating that athletes were able to maintain stable biomechanical parameters throughout the race. The conclusion highlights the need for personalized training programs tailored to the unique biomechanical adaptations and demands of endurance running.

Effects of running-induced fatigue on joint kinematics and kinetics during overground running: a systematic review and meta-analysis.

This study evaluated the acute fatigue-inducing effect of distance running on kinematics and kinetics during overground running. Standardised mean differences (SMD) with 95% confidence intervals (95% CI) were used to pool data across 16 studies. Effects during consistent (pre- and post-fatigue running speed within ± 5%) versus varied speed running (difference of >5% between running speeds) were analysed separately. There was strong evidence that running-induced fatigue significantly increases ground contact times at consistent running speeds (SMD 0.52 [95% CI 0.22, 0.82]) and moderate evidence that step length shortens at varied running speeds (SMD -1.27 [95% CI -1.79, -0.75]). There was strong evidence that fatigue does not change peak: hip and knee flexion angles, hip adduction angle, hip and knee internal rotation angles, hip and knee extension moments, hip and knee abduction moments, knee abduction angle, knee flexion and extension moments, knee adduction moment, rearfoot eversion angle, and plantarflexion moments, or knee flexion and plantarflexion range of motion during stance. Running-induced fatigue increases contact times and reduces step length, whereas lower-body joint angles and moments are unchanged. Minimising changes in stride parameters could provide a mechanism for reducing the effects of fatigue on running performance.

An Investigation of Running Kinematics with Recovered Anterior Cruciate Ligament Reconstruction on a Treadmill and In-Field Using Inertial Measurement Units: A Preliminary Study.

Anterior cruciate ligament reconstruction (ACLR) may affect movement even years after surgery. The purpose of this study was to determine possible interlimb asymmetries due to ACLR when running on a treadmill and in field conditions, with the aim of contributing to the establishment of objective movement assessment in real-world settings; moreover, we aimed to gain knowledge on recovered ACLR as a biomechanical risk factor. Eight subjects with a history of unilateral ACLR 5.4 ± 2.8 years after surgery and eight healthy subjects ran 1 km on a treadmill and 1 km on a concrete track. The ground contact time and triaxial peak tibial accelerations were recorded using inertial measurement units. Interlimb differences within subjects were tested and compared between conditions. There were no significant differences between limbs in the ACLR subjects or in healthy runners for any of the chosen parameters on both running surfaces. However, peak tibial accelerations were higher during field running (p-values < 0.01; Cohen's d effect sizes > 0.8), independent of health status. To minimize limb loading due to higher impacts during field running, this should be considered when choosing a running surface, especially in rehabilitation or when running with a minor injury or health issues.

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.

Assessing the reliability of biomechanical variables during a horizontal deceleration task in healthy adults

ABSTRACT Horizontal deceleration technique is an underpinning factor to musculoskeletal injury risk and performance in multidirectional sport. This study primarily assessed within- and between-session reliability of biomechanical and performance-based aspects of a horizontal deceleration technique and secondarily investigated the effects of limb dominance on reliability. Fifteen participants completed four horizontal decelerations on each leg during test and retest sessions. A three-dimensional motion analysis system was used to collect kinetic and kinematic data. Completion time, ground contact time, rate of horizontal deceleration, minimum centre of mass height, peak eccentric force, impulse ratio, touchdown distance, sagittal plane foot and knee angles at initial contact, maximum sagittal plane thorax angle, and maximum knee flexion moment were assessed. Coefficients of variation (COV) and intraclass correlation coefficients (ICC) were used to assess within- and between-session reliability, respectively. Seven variables showed “great” within-session reliability bilaterally (COV ≤9.13%). ICC scores were ‘excellent’ (≥0.91; n = 4), or ‘good’ (0.76-0.89; n = 7), bilaterally. Limb dominance affected five variables; three were more reliable for the dominant leg. This horizontal deceleration task was reliable for most variables, with little effect of limb dominance on reliability. This deceleration task may be reliably used to assess and track changes in deceleration technique in healthy adults.

Asymmetric running is associated with pain during outdoor running in individuals with Achilles tendinopathy in the return-to-sport phase

ObjectivesTo determine the relationships between (1) Achilles tendon pain and loading symmetry, and (2) number of running bouts and symptom severity, during two weeks of outdoor running in individuals with Achilles tendinopathy. DesignProspective, observational study. SettingBiomechanics laboratory and outdoors. ParticipantsSeventeen runners with Achilles tendinopathy in the return-to-sport phase of rehabilitation. Main outcome measuresSymptom severity was recorded with the Victorian Institute of Sports Assessment-Achilles (VISA-A) questionnaire. Running bouts and Achilles tendon pain during runs were recorded with daily training logs. Ground contact time was collected during runs with wearable sensors. Linear mixed modeling determined if the relationship between Achilles tendon pain and ground contact time symmetry during running was moderated by consecutive run days. Multiple regression determined the relationship between number of running bouts and change in VISA-A scores over two weeks, adjusted for run distance. ResultsGreater ground contact time on the contralateral leg corresponded to increased ipsilateral tendon pain for each consecutive run day (b = −0.028, p < 0.001). Number of running bouts was not associated with 2-week changes in VISA-A scores (p = 0.672). ConclusionsPain during running is associated with injured leg off-loading patterns, and this relationship strengthened with greater number of consecutive run days. Number of running bouts was not related to short-term symptom severity.