A method comparison study of accelarometer based block response times in sprinting

This study aimed to provide a method comparison of a rail mounted accelerometer for detection of block response-times (RT) with an International Association of Athletic Federation (IAAF) approved automatic start control system (IAAF RT). Twenty national and international sprinters completed sprint trials under simulated race conditions. An accelerometer was placed on the block rail of blocks and RT was determined using visual inspection of the accelerometer signal and using a 3SD threshold method. On average, the visual method detected the RT event 7 ms before, and the 3SD method detected RT 1 ms after the IAAF RT. The results indicated close agreement between the 3SD threshold method and the IAAF RT, however, this highlights the need for further re-examination of threshold-based detection algorithms which may delay the detection of the RT event

Profiling elite male 100-m sprint performance: The role of maximum velocity and relative acceleration

Purpose: This study aimed to determine the accuracy of a 4 split time modelling method to generate velocity-time and velocity-distance variables in elite male 100-m sprinters and subsequently to assess the roles of key sprint parameters with respect to 100-m sprint performance. Additionally, this study aimed to assess the differences between faster and slower sprinters in key sprint variables that have not been assessed in previous work. Methods: Velocity-time and velocity-distance curves were generated using a mono-exponential function from 4 split times for 82 male sprinters during major athletics competitions. Key race variables—maximum velocity, the acceleration time constant (t), and percentage of velocity lost (vLoss)—were derived for each athlete. Athletes were divided into tertiles, based on 100-m time, with the first and third tertiles considered to be the faster and slower groups, respectively, to facilitate further analysis. Results:Modelled split times and velocities displayed excellent accuracy and close agreement with raw measures (range of mean bias was –0.2% to 0.2%, and range of intraclass correlation coefficients (ICCs) was 0.935 to 0.999) except for 10-m time (mean bias was 1.6% ± 1.3%, and the ICC was 0.600). The 100-m sprint performance time and all 20-m split times had a significant near-perfect negative correlation with maximum velocity (r ≥ –0.90) except for the 0 to 20-m split time, where a significantly large negative correlation was found (r = –0.57). The faster group had a significantly higher maximum velocity and τ (p Conclusion:Coaches and researchers are encouraged to utilize the 4 split time method proposed in the current study to assess several key race variables that describe a sprinter's performance capacities, which can be subsequently used to further inform training. </p

Influence of triceps surae electromechanical delay on movement responses in the sprint start event

This study examined the delay in sprint start performance related to electromechanical delay (EMD) in the triceps surae muscle and aimed to determine whether sprinters may gain an advantage in sprint start response time (SSRT). SSRT’s of nineteen sprinters were measured using an International Association of Athletics Federations approved SSRT detection system. EMD times were also obtained from the triceps surae muscle during a simple heel-lift experiment. Using Brosnan et al. (2016) response time limits, the results demonstrated that EMD produced a significant moderate correlation with SSRT (r = 0.572, P = 0.01). Initial results suggest EMD influences SSRT. However greater specificity in the EMD measurement to the sprint start action is required to determine the true effects of EMD on SSRT

A comparison of hand force and starting block-based response times in the sprint start

This study provided a method comparison of sprint start response times (RTs) obtained using a custom designed hand force plate with block response-times (RT) from an International Association of Athletic Federation (IAAF) approved automatic start control system (IAAF RT). Twenty national and international sprinters completed sprint trials under simulated race conditions. The athletes’ hand forces were obtained using the hand force plate, which was electronically synchronised with the IAAF approved system. The results showed that in all trials, the hand plate RT occurred significantly before the IAAF RT with an average difference of 64 ms. The consistent differences in RT’s suggested that the two systems measured separate events. A re-evaluation of false start detection technology based on measuring hand RT is recommended

An exploration of eliminating cross-talk in surface electromyography using independent component analysis

The purpose of this study was to explore the use of Independent Component Analysis (ICA) on surface Electromyography (EMG) data to distinguish between individual muscle activations due to its capabilities for signal separation. EMG data was gathered on seven participants using the Delsys Trigno Wireless EMG system. Participants performed specific movements which targeted the calves muscle group of the lower leg. EMG sensors were attached according to SENIAM recommendations and extra sensors were attached in non-recommended locations to achieve crosstalk. Signals were acquired using proprietary Delsys software and processed using the ICA algorithm in Matlab to explore crosstalk. Integrated EMG was calculated for all results using custom Matlab code. The results showed moderate levels of agreement between the mixed signals and the original signals (p < 0.01). However, further work is needed to determine the usefulness of the independent components

A survey of sensor devices: use in sports biomechanics

This paper examines the use of sensor devices in sports biomechanics, focusing on current frequency of use of Electromyography (EMG) device preferences. Researchers in the International Society of Biomechanics in Sports were invited to participate in an online survey. Responses on multiple sensor devices highlighting frequency of use, device features and improvements researchers sought in acquisition and analysis methods were obtained via an online questionnaire. Results of the investigation showed that the force platform is the most frequently used device, with inertial measurement units and EMG devices growing in popularity. Wireless functionality and ease of use for both the participant and the practitioner proved to be important features. The main findings of the survey demonstrated need for a simple, low power, multi-channel device which incorporates the various sensors into one single device. Biomechanists showed they were looking for more availability of wireless sensor devices with acquisition and analysis features. The study found there is a need to develop software analysis tools to accompany the multi-channel device, providing all the basic functions while maintaining compatibility with existing systems

Estimation of force during vertical jumps using body fixed accelerometers

A method of estimating force using an accelerometer is presented. This model is based on estimating the resultant acceleration of a body at its centre of mass using a triaxial accelerometer. A data set of ground reaction forces are gathered using a force platform, which is used as the control for this experiment. Signal processing techniques for resampling the accelerometer signals, along with a method of cross correlation to align the force platform and accelerometer traces are used. The purpose of this study was to compare force calculated using accelerometer data from the SHIMMER device, with force platform data on counter movement and drop jumps, for use in sports biomechanics. The method was validated using twelve physically active adults who performed 5 counter movement jumps and 5 drop jumps from a height of 0.30 m. An accelerometer was attached near the participant’s centre of mass and simultaneous force and acceleration data were obtained for the jumps. Minimum eccentric force and peak concentric force were calculated concurrently for countermovement jumps and peak landing forces were calculated concurrently for drop jumps. The results showed moderate to low levels of agreement in forces and a consistent systematic bias between the results from the force platform and accelerometer. However, good agreement between the accelerometer and force platform was observed during the eccentric phase of the countermovement jump

The use of Independent component analysis on EMG data to explore cross-talk

The purpose of this study was to explore the use of Independent Component Analysis (ICA) on Electromyography (EMG) data to distinguish between individual muscle activations due to its capabilities of signal separation. EMG data was gathered on seven participants using the Delsys Trigno Wireless EMG system. Participants performed movements which targeted the quadriceps muscle group. EMG sensors were attached according to SENIAM recommendations and extra sensors were attached in non-recommended locations. Signals were gathered and passed through an ICA algorithm to explore crosstalk. The results showed moderate levels of agreement in mixed signals and original signals

An EMG profile of lower limb muscles during linear glide and standing shot putting

The purpose of this study was to provide a descriptive analysis of the phasic muscle activity of 8 lower limb muscles during performance of the shot put field event in track and field athletics. Six shot putters performed 3 standing and 3 full linear glide technique throws. Electromyography (EMG) of 8 lower limb muscles was recorded during the trials and the distance thrown was also measured. A comparison between standing and glide techniques are important from a coaching perspective. An increase in peak muscle activity of the Rectus Femoris was observed between the glide and standing throw, all other lower limb muscles showed no significant increases between the techniques. Results show significant increases between performances of standing and glide throws in female athletes however the mean differences were smaller in the male athletes

Reliability of mechanical properties of the plantar flexor muscle tendon unit with consideration to joint angle and sex

The reliability of mechanical measures can be impacted by the protocol used, including factors such as joint angle and the sex of participants. This study aimed to determine the interday reliability of plantar flexor mechanical measures across ankle joint angles and contraction types and consider potential sex-specific effects. 14 physically-active individuals participated in two identical measurement sessions involving involuntary and voluntary plantar flexor contractions, at three ankle angles (10˚ plantarflexion (PF), 0˚ (anatomical zero (AZ)), and 10˚ dorsiflexion (DF)), while torque and surface EMG were recorded. The reliability of mechanical parameters of maximal voluntary torque (MVT), rate of torque development (RTD), electromechanical delay, and tendon stiffness were assessed using absolute and relative reliability measures. MVT measures were reliable across ankle angles. RTD measures showed good group level reliability and moderate reliability for an individual during the early phase of contraction across ankle angles. Explosive voluntary torque measures tended to be less reliable from 50 ms onward, with varied reliability across angles for late-phase RTD. Tendon stiffness demonstrated the best reliability at the DF angle. Sex-based differences in the reliability of tendon measures found that females had significantly different initial tendon length between testing sessions. Despite this, tendon excursion, force, and stiffness measures demonstrated similar reliability compared to males. Ankle angle changes influence the reliability of plantar flexor mechanical measurements across contraction types, particularly for voluntary contractions. These results highlight the importance of establishing potential protocol effects on measurement reliability prior to quantifying plantar flexor mechanical measures.</p