Prediction of Throwing Distance in the Men’s and Women’s Javelin Final at the 2017 IAAF World Championships

The purpose of this study was to use regularised regression models to identify the most important biomechanical predictors of throwing distance in elite male (M) and female (F) javelin throwers at the 2017 IAAF world championships. Biomechanical data from 13 male and 12 female javelin throwers who competed at the 2017 IAAF world championships were obtained from an official scientific IAAF report. Regularised regression models were used to investigate the associations between throwing distance and release parameters, whole-body kinematic and joint-level kinematic data. The regularised regression models identified two biomechanical predictors of throwing distances in both M and F javelin throwers: release velocity and knee flexion angle of the support leg at the moment of javelin release. In addition, the length of the delivery stride was an important predictor of throwing distance in M throwers, whereas the javelin’s attitude angle and the distance between the whole-body centre of mass and the centre of mass of the back foot at the beginning of the delivery phase were important predictors of throwing distance in F throwers

Use of Machine Learning to Model Volume Load Effects on Changes in Jump Performance

Purpose: To use an artificial neural network (ANN) to model the effect of 15 weeks of resistance training on changes in countermovement jump (CMJ) performance in male track-and-field athletes. Methods: Resistance training volume load (VL) of 21 male division I track-and-field athletes was monitored over the course of 15 weeks, which covered their indoor and outdoor competitive season. Weekly CMJ height was also measured and used to calculate the overall 15-week change in CMJ performance. A feed-forward ANN with 5 hidden layers was used to model how the VL from each of the 15 weeks was associated with the overall change in CMJ height. Results: Testing the performance of the developed ANN on 4 separate athletes showed that 15 weeks of VL data could predict individual changes in CMJ height with an average error between 0.21 and 1.47 cm, which suggested that the ANN adequately modeled the relationship between weekly VL and its effects on CMJ performance. In addition, analysis of the relative importance of each week in predicting changes in CMJ height indicated that the VLs during deload or taper weeks were the best predictors (10%–17%) of changes in CMJ performance. Conclusions: ANN can be used to effectively model the effects of weekly VL on changes in CMJ performance. In addition, ANN can be used to assess the relative importance of each week in predicting changes in CMJ height

EFFECTS OF MAXIMAL STRENGTH ON GROUND REACTION FORCE PATTERNS DURING COUNTERMOVEMENT JUMPS

The purpose of this study was to determine the effects of maximal strength on ground reaction force (GRF) patterns during countermovement jumps (CMJ). Nineteen female lacrosse players performed CMJ and isometric mid-thigh pulls (IMTP) on force plates. Principal components analysis was used on the CMJ time series data to extract GRF patterns. Maximum GRF during the IMTP were extracted and used as a measure of maximal strength. Spearman’s rho correlations were used to analyse the relationship between maximal strength and GRF patterns during the CMJ. Results suggest that maximal strength is positively correlated to a GRF CMJ pattern characterised by greater rate of force development and peak force as well as less of a decrease in GRF immediately after the end of the eccentric phase (i.e., absence of bimodal GRF profile)

Comparison of Walking Mechanics between Manual and Automated IV Poles

Many older adults fall while admitted in the hospital. The increased incidence of hospital falls is associated with intravenous (IV) pole manipulation when maneuvering through the room. PURPOSE: To determine whether an automated IV pole can decrease fall risk in older adults. METHODS: Twelve healthy older adults (\u3e 65 years) performed three walking trials for each of three walking conditions (normal walking [no IV pole], walking with a manual IV pole, and walking with an automated IV pole [robot]). Each walking trial consisted of three phases: walking up to a door (entry), opening the door (door), and walking through the door (exit). Performance (entry velocity, exit velocity, door manipulation time, and smoothness defined by total body jerk during entry, door manipulation, and exit) and postural (reach distance, posterior displacement) kinematic variables were analyzed and compared among the walking conditions. The no IV pole condition was used as a control, with deviations in walking mechanics during manual and robot conditions assessed relative to increased fall risk. RESULTS: Compared to no IV pole, entry and exit velocity significantly decreased in manual (entry: 15.4%, exit: 35.5%) and robot (entry: 18.3%, exit: 30.9%) walking trials (P\u3c0.001), while door manipulation time significantly increased in manual (36.4%, P=0.002) and robot (19.0%, P=0.028) walking trials. The manual IV pole required greater posterior displacement compared to no IV pole (113.3%) and robot (146.2%) walking trials (P\u3c0.001), while reach distance was significantly greater compared only to no IV pole (14.6%, P=0.009). Gait smoothness during entry (entry jerk) was significantly less in robot walking trials compared to no IV pole (5.9%, P=0.038), while exit jerk was significantly less in the manual walking trial compared to the robot trial (20.3%, P=0.007). Compared to no IV pole walking trials, the manual IV pole produced greater door manipulation jerk (14.3%, P=0.043). CONCLUSION: The present study demonstrates an automated IV pole can reduce certain kinematic factors related to fall risk when maneuvering a manual IV pole. The apparent high potential from this study for use of automated IV poles in clinical settings with patient populations warrants further exploration and development with respect to the efficacy of automated IV poles. Supported by SmartMate Solutions LL

Relationships among Countermovement Vertical Jump Performance Metrics, Strategy Variables, and Inter-limb Asymmetry in Females

Dependent variables commonly studied during countermovement vertical jump (CMVJ) tests largely stem from male-only studies despite females’ distinct energy storage and reutilization strategies. This could limit progress among females seeking increased CMVJ performance through targeted changes in certain variables. We explored relationships between CMVJ performance metrics (jump height, modified reactive strength index, jump power, and takeoff momentum) and a) temporal and force application variables and b) inter-limb force and yank (i.e., rate of force development) asymmetry in 31 recreationally active females. Participants performed 8 CMVJs while ground reaction force (GRF) data were obtained. Pearson product-moment correlation coefficients assessed the strength and direction of the associations. Twenty-six significant relationships (r≥±0.357; p<0.05) were detected across the CMVJ performance variables. The significantly correlated variables were generally isolated to only one of the four performance metrics. Only the percentage of concentric phase inter-limb force asymmetry was significantly associated with CMVJ performance, specifically jump power and takeoff momentum. Coaches and physical performance professionals should be aware of popular strategy variables’ association or lack of association with commonly studied performance metrics when seeking to understand or improve specific CMVJ jumping abilities in females

PREDICTION OF THROWING DISTANCE IN THE MEN\u27S JAVELIN AT THE 2017 IAAF WORLD CHAMPIONSHIPS

The purpose of this study was to identify key biomechanical parameters that predict throwing distance in elite male javelin throwers. Biomechanical data from 13 male javelin throwers who competed at the 2017 IAAF World Championships were obtained from a freely available IAAF report. A regularised regression model was used to determine the associations between throwing distance and release parameters, whole-body kinematic, and joint-level kinematic data. The model indicated that delivery step distance (r = 0.69), release velocity (r = 0.85), distance between left foot and javelin grip at the beginning of the delivery phase (r = 0.47), and the angle of the support leg’s knee joint at the instance of release (r = 0.56) were all important predictors of throwing distance in elite male javelin throwers at the 2017 IAAF World Championships

Load-Dependent Mechanical Demands of the Lower Extremity During the Back and Front Squat

The purpose of this study was to examine load-dependent differences in lower-extremity biomechanics between the back squat (BS) and front squat (FS) exercises. Eleven NCAA Division-I athletes performed three repetitions of the BS and FS at loads of 40%, 60%, and 80% of their FS one repetition maximum (FS-1RM). Kinematic and kinetic data were collected during each squat repetition and used to calculate lower extremity peak joint angles and peak net joint moments (NJM). Peak angles and NJM were compared with a 2 × 3 repeated measures ANOVA. Peak hip extensor NJM were greater during the BS at 60% and 80% of FS-1RM. In comparison, peak knee extensor NJM were greater during the FS at 80% of FS-1RM. However, regression-based prediction of NJM at 100% of FS and BS 1RM indicated that at maximal loads, peak knee NJM are (~3%) higher during the BS. The experimental results suggest that when performed at the same absolute load, the BS and FS are characterized by greater respective mechanical demands imposed on the hip and knee extensors muscles groups. However, prediction-based results suggest that the knee extensor NJM demands are comparable when performed at the same relative load (i.e., with respect to each exercise’s RM)

Hip Moment and Knee Power Eccentric Utilisation Ratios Determine Lower-Extremity Stretch-Shortening Cycle Performance

The eccentric utilisation ratio (EUR) is calculated as the ratio between countermovement jump (CMJ) and squat jump (SJ) heights, and is an indicator of lower-extremity stretch-shortening cycle (SSC) performance in athletes. Joint-based EUR can also be calculated but have never been reported. The purpose of this study was to investigate whether jump height-based (JH-based) EUR can be predicted by joint-specific EUR. Nine NCAA Division I college athletes (age: 21 ± 1 year, height: 1.75 ± 0.15 m, mass: 71 ± 20 kg) performed three SJ and CMJ. During all jumps, kinematic and kinetic data were obtained and used to calculate hip, knee and ankle net joint moments (NJM) and net joint powers (NJP). JH was calculated from pelvis marker data. EUR (CMJ/SJ [unitless]) were calculated for JH, NJM, and NJP. JH-EUR was 1.11 ± 0.70. NJM-EUR were 1.07 ± 0.17, 1.17 ± 0.25, and 1.07 ± 0.18 for the hip, knee and ankle joint, respectively. NJP-EUR were 1.41 ± 0.12, 1.26 ± 0.28 and 1.06 ± 0.11 for the hip, knee and ankle joint, respectively. Regularised regression showed that Hip-NJM-EUR, Knee-NJP-EUR and Ankle-NJM-EUR were able to predict 83% of the variance in JH-EUR, which suggests that the enhancement of lower-extremity SSC performance during CMJ arises from a combination of these parameters

Maximal Strength in Relation to Force and Velocity Patterns During Countermovement Jumps

Maximal strength is important for the performance of dynamic athletic activities, such as countermovement jumps (CMJ). Although measures of maximal strength appear related to discrete CMJ variables, such as peak ground reaction forces (GRF) and center-of-mass (COM) velocity, knowledge about the association between strength and the time series patterns during CMJ will help characterize changes that can be expected in dynamic movement with changes in maximal strength. Purpose: To investigate the associations between maximal strength and GRF and COM velocity patterns during CMJ. Methods: Nineteen female college lacrosse players performed 3 maximal-effort CMJs and isometric midthigh pull. GRF and COM velocity time series data from the CMJ were time normalized and used as inputs to principal-components analyses. Associations between isometric midthigh pull peak force and CMJ principal-component scores were investigated with a correlational analysis. Results: Isometric midthigh pull peak force was associated with several GRF and COM velocity patterns. Correlations indicated that stronger players exhibited a GRF pattern characterized by greater eccentric-phase rate of force development, greater peak GRF, and a unimodal GRF profile (P = .016). Furthermore, stronger athletes exhibited a COM velocity pattern characterized by higher velocities during the concentric phase (P = .004). Conclusions: Maximal strength is correlated to specific GRF and COM velocity patterns during CMJ in female college lacrosse athletes. Since maximal strength was not correlated with discrete CMJ variables, the patterns extracted via principal-components analyses may provide information that is more beneficial for performance coaches and researchers