François-Xavier Li

• University of Birmingham

Langdown, BL, Bridge, MW, and Li, F-X. The influence of an 8-week strength and corrective exercise intervention on the overhead deep squat and golf swing kinematics. J Strength Cond Res XX(X): 000-000, 2022-It has previously been suggested that performance of the overhead squat (OHS) is a useful predictor of loss of posture in the golf swing. Using...

Objectives We examined the relation between global positioning system (GPS)-derived workloads and injury in English Premier League football players (n=33) over three seasons. Methods Workload and injury data were collected over three consecutive seasons. Cumulative (1-weekly, 2-weekly, 3-weekly and 4-weekly) loads in addition to acute:chronic work...

The swimrun is a new endurance team-sport based on two persons swimming and running alternatively through open water and mostly trails. The aim of this study was to analyse participation and performance trends for males, females and mixed duo team at the ÖTILLÖ Swimrun race (10km open-water swimming and 65km trail running). During the 2012-2016 per...

Plastic surgeons report neck, shoulder and back pain when wearing head-mounted magnifiers (loupes) during operations. There will be many factors contributing to such pain. In order to explore these factors this paper developed a novel application of Multi-objective Optimization (MOO) which used postural constraints on anthropometric models to deter...

Objective: To review the literature comparing use of anterior and posterior walkers (PW’s) by children with cerebral palsy (CP) to determine which walker type is preferable. Methods: Electronic databases were searched using pre-defined terms by two independent reviewers. Reference lists of included studies were hand searched. Studies published betw...

Ageing is associated with a decline in muscle strength and impaired sensory mechanisms which contribute to an increased risk of falls. Walking barefooted has been suggested to promote increased muscle strength and improved proprioceptive sensibility through better activation of foot and ankle musculature. Minimalist footwear has been marketed as a...

Aim The purpose of this study was to investigate the relationship between physical workload and injury risk in elite youth football players. Methods The workload data and injury incidence of 32 players were monitored throughout 2 seasons. Multiple regression was used to compare cumulative (1, 2, 3 and 4-weekly) loads and acute:chronic (A:C) worklo...

For the first time, an extensive numerical study of the effect of crosswinds on the flow around a cyclist on a bicycle with stationary wheels has been undertaken for crosswind (yaw) angles ranging from 0° to 90°. The flow field and the aerodynamic forces have been obtained using three numerical techniques: Reynolds Averaged Navier Stokes (RANS), De...

Habitual footwear use has been reported to influence foot structure with an acute exposure being shown to alter foot position and mechanics. The foot is highly specialised thus these changes in structure/position could influence functionality. This review aims to investigate the effect of footwear on gait, specifically focussing on studies that hav...

To reduce air resistance, time trial cyclists and triathletes lower their torso angle. The aim of this study was to investigate the effect of lowering time trial torso angle positions on muscle activation patterns and crank torque coordination. It was hypothesized that small torso angles yield a forward shift of the muscle activation timing and cra...

Research on how human balance and control bicycles are inconclusive, largely due to the small number of participants in the previous studies. Therefore, the aim of this study was to test the hypotheses that 1) cycling lateral deviation amplitude will reliably show differences between more and less experienced cyclists and 2) more experienced will e...

Abstract To reduce aerodynamic resistance cyclists lower their torso angle, concurrently reducing Peak Power Output (PPO). However, realistic torso angle changes in the range used by time trial cyclists have not yet been examined. Therefore the aim of this study was to investigate the effect of torso angle on physiological parameters and frontal ar...

Crosswinds have the potential to influence the stability and therefore the safety of a motorbike rider. Numerical computations using both delayed detached-eddy simulations (DDES) and Reynolds-Averaged Navier-Stokes (RANS) were employed to investigate the flow around a motorbike subjected to crosswinds with yaw angles of 15, 30, 60 and 90 degrees. T...

The aims of this research were to firstly investigate the effect of crosswinds on the aerodynamic behaviour of cyclists and secondly, to determine which parameters (cyclist position and bike type) influenced the aerodynamic forces on cyclists the most. The aerodynamic response of two different full-scale bikes with and without a mannequin has been...

Previous studies have employed relatively short cycling protocols to investigate the effect of cycling on muscle activation and kinematics in running. The aim of this study was to investigate the effect of three hours of cycling on stride time variability (STV), stride length, tibialis anterior (TA) activation, and lower limb range of motion (ROM)...

Background: According to the Statistical Release by the Department for Transport, in the United Kingdom 19.000 cyclists are killed or seriously injured every year, with losing control being one of the most common reasons. Research on bike handling went under a revival, but it is still inconclusive on how humans balance and control trajectories and...

Background: Bike handling skills aimed to maintain balance are important to prevent falling off the bike and/or crashing into obstacles. Past research on dynamics and control of bicycles is inconclusive on how human balance during cycling and how they control trajectories and direction during cycling (Moore et al.,. Purpose: Our aim was to develop...

The aerodynamic drag of a cyclist in time trial (TT) position is strongly influenced by the torso angle. While decreasing the torso angle reduces the drag, it limits the physiological functioning of the cyclist. Therefore the aims of this study were to predict the optimal TT cycling position as function of the cycling speed and to determine at whic...

Abstract The most common bike fitting method to set the seat height is based on the knee angle when the pedal is in its lowest position, i.e. bottom dead centre (BDC). However, there is no consensus on what method should be used to measure the knee angle. Therefore, the first aim of this study was to compare three dynamic methods to each other and...

Correct bicycle fit is important, and kinematic instability must be addressed to reduce the risk of knee injury. A change in Q Factor (horizontal distance between crank arms) has been shown to decrease metabolic cost. The combined effect upon gross mechanical efficiency (GME) and knee variability is unclear, however; there is no known simple method...

This study examined the variable error (VE) for the golf impact position of high and low skilled golfers. A consistent shot type was employed by 20 golfers from 2 skill groups over 10-15 shots with a midiron. Analysis reported similar positional variability across categories. Significant differences were found for the whole group in VE of the dista...

Large alterations to the preferred running stride decrease running economy, and shorter strides increase leg muscle activity. However, the effect of altered strides on the timing of leg muscle activation is not known. The aim of this study was to evaluate the impact of moderate alterations to the running stride on running economy and the timing of...

This study aimed to determine whether differences in variability at address exist between golfers of low and high handicaps. A consistent shot type was employed by 20 golfers from 2 skill groups over 10–15 shots with a midiron. Kinematics analysis revealed only one significant difference between skill levels: the alignment relationship between the...

In order to understand muscle adaptations to altered task mechanics during cycling, this study investigated the impact of altered seat height and cadence on timing and duration of gastrocnemius (GAST), biceps femoris (BF) and vastus lateralis (VL) eccentric contractions and muscle activation patterns, and cycling economy. Ten male cyclists complete...

Traditionally, golf biomechanics has focused upon achieving consistency in swing kinematics and kinetics, whilst variability was considered to be noise and dysfunctional. There has been a growing argument that variability is an intrinsic aspect of skilled motor performance and plays a functional role. Two types of variability are described: 'strate...

Unexplored in scientific literature, Q Factor describes the horizontal width between bicycle pedals and determines where the foot is laterally positioned throughout the pedal stroke. The aim of the study was to determine whether changing Q Factor has a beneficial effect upon cycling efficiency and muscular activation. A total of 24 trained cyclists...

The treatment of most injuries tends to have similar goals: to minimize initial pain and swelling, restore full range of motion, and return to full strength. One of the key problems is the gap between the traditional rehabilitation modalities and progression to normal locomotive and athletic activities. Closed kinetic chain exercises are a common f...

The authors performed an experiment in which participants (N = 24) made judgments about maximum jump and reachability on ground surfaces with different elastic properties: sand and a trampoline. Participants performed judgments in two conditions: (a) while standing and after having recently jumped on the surface in question and (b) while standing o...

The variability in elite table tennis players’ bat movement direction was shown qualitatively by Bootsma et al. (1990) to ‘‘funnel’’ or become reduced towards bat-ball contact. Scott et al. (1997) showed that novice long jumpers’ foot-placement variability followed a similar pattern of reducing variability that was also found previously for experts...

Studies on affordance perception commonly report systematic errors; a finding that is at odds with the observation that everyday motor behavior is accurate. The present study investigated whether the means by which perceptual performance is measured could explain the reported errors. Perception of overhead reachability and reaction time were measur...

In this study, we examined the effect of string vibration damping devices on reducing racket frame vibration transfer to the forearm. Twenty participants volunteered to hold a tennis racket stationary in a forehand and backhand stroking position while tennis balls were fired at 20 m x s(-1) towards two impact locations, the node of vibration and th...

During object manipulation, both predictive feedforward and reactive feedback mechanisms are available to adjust grip force (GF) levels to compensate for the destabilizing effects of load force changes. During collisions, load force increases impulsively (< 20 ms). Thus, only predictive control of GF can be used to ensure grasp stabilization. A col...

Magnesium carbonate, or 'chalk', is used by rock climbers to dry their hands to increase the coefficient of friction, thereby improving the grip of the holds. To date, no scientific research supports this practice; indeed, some evidence suggests that magnesium carbonate could decrease the coefficient of friction. Fifteen participants were asked to...

As an aid to studying the efficiency of grip force scaling in the context of collisions, we present a simple cost-effective approach to estimating the slip ratio--that is, the minimum grip-to-load-force ratio needed to prevent object slippage. The grip apparatus comprises a sturdy load cell to measure grip force and two linear potentiometers to pro...

Animals generally seek to avoid potentially harmful collisions. To perform successful avoidance, actors must correctly perceive the approach of an object and produce an appropriate motor response. Objects can approach from any part of the visual field, but avoidance skills are particularly relevant when threatening approaches occur in peripheral vi...

Specifications of affordances is independent of the anthropometric scale of the perceiver. It is therefore predicted that sex differences disappear when perceptual performance is scaled relative to the relevant physical properties of the system formed by performer and environment in a particular action. 24 women and 30 men were compared for their a...

Specifications of affordances is independent of the anthropometric scale of the perceiver. It is therefore predicted that sex differences disappear when perceptual performance is scaled relative to the relevant physical properties of the system formed by performer and environment in a particular action. 24 women and 30 men were compared for their a...

Specification of the relevant properties of environment and actor enables the perception of affordances. In the present paper it is emphasised that affordances are dynamic and that to accurately perceive affordances the relevant geometric and kinetic properties of the Environment-Actor System (EAS) have to be perceived. The reach-with-jump action i...

This experiment investigated the prediction of load force (LF) in impulsive collisions inferred from anticipatory adjustments of grip force (GF) used to stabilise a hand-held object. Subjects used a precision grip to hold the object between thumb and index finger of their right hand and used the arm either: (1) to move the object to produce a colli...

In the approach phase of the long jump, athletes attempt to strike the take-off board accurately with minimum loss of speed, and in an optimum body position for take-off. Previous research has shown that skilled long jumpers demonstrate an ascending-descending trend of variability rather than a consistent pattern of foot placement over trials. The...

Tresilian (1991) identified two mathematical forms of Local Tau as candidates for perceiving time to-contact information. Local Tau 1 (LT1) only requires the physical distance between two points on the approaching object to remain constant in relation to each other over time. Local Tau 2 (LT2) requires the complete outline of the object to remain c...

When a ball is rolling on the ground toward an observer, its elements of texture are successively occluded. The number of the elements of texture occluded per unit of time determines the occlusion rate. The aim of this study was to examine the role of the occlusion rate of ball texture and the velocity of the ball in the perception of the time rema...

In order to perform a coincidence-timing task, such as avoiding, hitting or catching an oncoming object, the control of the movement has to take into account the features of the environment. Li and Laurent (1994) observed that timing and movement velocity of such behaviours are coupled with the velocity of the object. In particular, with the increa...