TRACKING OF STRENGTH TRAINING: VALIDATION OF A MOTION-RECOGNITION ALGORITHM & A PILOT TOWARDS 1RM, MUSCLE LOADING AND FATIGUE INDEX USING A SMARTWATCH APP

Ubiquitous wrist-worn devices have become a noteworthy research topic in motion recognition of strength training exercises. This study was designed to develop a watchOS and iOS application and assess its exercise recognition and repetition counting accuracy. Furthermore, as a pilot, a method to estimate the 1 repetition maximum and muscle stress and fatigue is explored. To test the exercise recognition and repetition counting accuracy, a workout consisting of nine sets with five randomly ordered resistance training exercises and repetition amounts was conducted when wearing an Apple Watch. Overall mean %error in exercise recognition was 3.5% and 0.92% in repetition counting. In the future, this app can also be used for estimation of 1 repetition maximum, muscle stress and fatigue

INFLUENCE OF STANCE WIDTH AND BINDING ANGLES ON TIBIAL ROTATION AND OLLIE JUMP HEIGHT IN SNOWBOARDING

The purpose of this study was to investigate the influence of stance width and binding angles on tibial rotation during a flat landing of a drop jump and Ollie jump height in snowboarders. Six binding conditions combined of three stance widths and two binding angle setups (forward and duck stance) were tested on 10 expert freestyle snowboarders. Relating to knee injury risk, tibial rotation was assessed using skin markers during the flat landing of a 51cm drop jump. The influence on the performance was investigated by the assessment of the Ollie jump height using a Quattro Jump force plate. An influence of the binding parameters on tibial rotation during a flat landing was found, whereas Ollie jump height didn’t differ significantly. A bigger angle of the front foot and a negative angle of the rear foot reduced the magnitude of internal tibial rotation

The impact of test loads on the accuracy of 1RM prediction using the load-velocity relationship

Numerous methods have been proposed that use submaximal loads to predict one repetition maximum (1RM). One common method applies standard linear regression equations to load and average vertical lifting velocity (V; mean; ) data developed during squat jumps or three bench press throw (BP-T). The main aim of this project was to determine which combination of three submaximal loads during BP-T result in the most accurate prediction of 1RM Smith Machine bench press strength in healthy individuals.; In this study combinations of three BP-T loads were used to predict 1RM Smith Machine bench press strength. Additionally, we examined whether regression models developed using peak vertical bar velocity (V; peak; ), rather than V; mean; , provide the most accurate prediction of Smith Machine bench press 1RM. 1RM Smith Machine bench press strength was measured directly in 12 healthy regular weight trainers (body mass=80.8±5.7 kg). Two to three days later a linear position transducer attached to the collars on a Smith Machine was used to record V; mean; and V; peak; during BP-T between 30 and 70% of 1RM (10% increments).; Repeated measures analysis of variance testing showed that the mean values for slope and ordinate intercept for the regression models at each of the load ranges differed significantly depending on whether V; mean; or V; peak; were used in the prediction models (; P;  < 0.001). Conversely, the abscissa intercept did not differ significantly between either measure of vertical bar velocity at each load range. The key finding in this study was that 1RM Smith Machine bench press strength can be determined with high relative accuracy by examining V; mean; and V; peak; during BP-T over three loads, with the most precise models using V; peak; during loads representing 30, 40 and 50% of 1RM (; R; 2;  = 0.96,; SSE;  = 4.2 kg).; These preliminary findings indicate that exercise programmers working with normal healthy populations can accurately predict Smith Machine 1RM bench press strength using relatively light load Smith Machine BP-T testing, avoiding the need to expose their clients to potentially injurious loads

MOMENTS IN THE KNEE AND HIP DURING DESCENT AND ASCENT OF SQUATS

The aim of this study was to compare the moments in the knee and hip during the acceleration phases, namely the descent and the ascent phase of squats. 20 subjects executed barbell squats with zero, 25 %, and 50 % body weight (BW) extra load. Based on motion capture and force data, an inverse dynamic calculation of the load condition of knee and hip was performed. The free chosen time for one repetition was less than 2 s. According to Newton’s second law, it is expected that during the acceleration phases of the body and the extra load, the load conditions are higher. The experimental data shows only shows small differences in the range of a few percent during the acceleration and deceleration phases of the squat. Therefore, the main part of the loading during squatting is based on the body weight and the barbell and not due to the acceleration of the mass

VELOCITY BASED STRENGTH TRAINING: VALIDITY OF THE APPLE WATCH 7 TO MEASURE MOVEMENT VELOCITY IN THE BACK SQUAT

Velocity-Based resistance Training (VBT) measurement methods based on commercially-available electronics in smartphones and other wearables are not yet accessible to the broad public. Building on this gap, the motivation for this study was to assess the validity of the Apple Watch 7 for broad application to VBT. In particular, the velocity predictions of a barbell mounted Apple Watch 7 were compared against data from 3D optical motion capture (Vicon) as gold standard in 22 subjects for the free weight back squat. The subjects reported to the lab for one testing session and performed the free weight back squat at intensities between 45 and 100 percent of their one-repetition-maximum. A total of 574 repetitions (total), 285 repetitions (slow), 289 repetitions (fast) were successfully recorded, with only 30 repetitions missing because of connection issues between the Apple Watch and the server infrastructure. The peak and mean velocity predictions of the concentric movement phase were with a high precision compared to Vicon (Vmean: SEE=0.049m/s, r=0.976, Vpeak: 0.092m/s, r=0.959), with the error being similar or smaller compared to other validation studies. The insight gained in this work plays a crucial part toward advancing VBT monitoring technologies for broader use by demonstrating the validity of commercially-available and highly popular consumer electronics

Energy transformation on vault in elite artistic gymnastics: comparisons between simple and difficult Tsukahara and Yurchenko vaults

Performance on vault in artistic gymnastics depends on the difficulty and the execution quality of the performed vault. However, differences of kinetic energy between simple and difficult vaults remain elusive. Therefore, in this study, 48 Tsukahara and Yurchenko vaults, performed by 20 top-level gymnasts, were recorded with 3D-motion capture and the flux of translational (TKE), angular kinetic (AKE), potential (PE), and total energy were calculated and compared. Results revealed that upon initial springboard contact, almost all of the kinetic energy for Tsukahara vaults is comprised of TKE, whereas Yurchenko vaults were characterized by substantially less TKE, but far greater AKE (and similar PE). During springboard contact of Tsukahara vaults, AKE is increased (+70%) and thereafter mostly preserved during push off from the table (−6%). For Yurchenko vaults, AKE is preserved during springboard contact but reduced (−30%) in exchange for PE at push off. During the second flight phase of Yurchenko vaults, total energy was 10% higher than at initial springboard contact (Tsukahara: −1%). For vaults of increasing difficulty, 5.9% more AKE is needed for each additional 180° of longitudinal-axis rotation. This knowledge may help coaches evaluate athletes’ potential and focus training on appropriate physical and/or technical aspects of the vault performance

KINEMATICS AND KINETICS OF SQUATS, DROP JUMPS AND IMITATION JUMPS OF SKI JUMPERS

The purpose of this study was to find objective factors in athleticism training which influence the performance of ski jumpers on the hill. Therefore, barbell squats, drop jumps and imitation jumps were measured in a laboratory environment for ten ski jumpers. Force and motion capture data was gathered and forces, velocities as well as an index for the knee valgus were calculated. The results show that especially for the imitation jumps there is a good correlation of the take-off velocity with the performance on the hill. What surprised more is that the more the athletes tended to a knee valgus during all measured movements, the worse the performance. Therefore, athleticism training should concentrate more on improving the knee stability

BIOMECHANICAL ANALYSIS OF SCHWINGEN (SWISS WRESTLING) TO GAIN INSIGHTS INTO HEAD, NECK AND KNEE INJURY RISKS

This research project aims to reduce incidences of injuries to the head, neck and knee in schwingen (Swiss wrestling) by means of biomechanical analysis. In this pilot study, kinematic and kinetic data were acquired during key manoeuvres in schwingen for the first time. Two professional athletes at Swiss national level in schwingen were performing the so-called Kurz, the Hüfter and the bridge in a simulated competitive setting. The peak vertical ground reaction force, acting on the back as the opponent was hitting the ground during the Hüfter, was measured to be 11500 N; while the peak vertical ground reaction force on the head during the bridge was 2360N, respectively. The knee flexion angle of the leading leg during the Kurz was 55°, with the total knee joint forces being 410N in the anterior-posterior direction and 400N in the medio-lateral direction, respectively. In comparison with reported cervical spine injury risks in American football and sumo wrestling, injury mechanisms at the level of the head, neck and knee in schwingen are likely a result of the applied forces from dynamic throws, in combination with extreme joint ranges of motion during fixed grips and defensive manoeuvres such as the bridge. An extended biomechanical analysis of the applied forces, moments and joint kinematics during schwingen is recommended to develop targeted injury prevention guidelines

the journal of functional morphology and kinesiology journal club series highlights on recent papers in gait and posture

We are glad to introduce the third Journal Club. The third edition is focused on several relevant studies published in the last years in the field of Gait and Posture, chosen by our Editorial Board members. We hope to stimulate your curiosity in this field and to share with you a passion for sport seen also from the scientific point of view. The Editorial Board members wish you an inspiring lecture

INFLUENCE OF THE STEP LENGTH AND POSITION OF THE FRONT KNEE ON THE LOAD CONDITIONS OF THE KNEE AND HIP DURING LUNGES

The aim of this study was to quantify the differences in the loading conditions of the lunge strength exercise at different step lengths and different tibia angles of the front leg. Eleven subjects performed lunges with 25 % body mass (BM) barbell extra load on two force plates. The movement was recorded with a motion capture system. The angles and the forces were calculated using inverse dynamics. A larger tibia angle led to a smaller ROM of the front knee, a larger ROM of the rear knee and hip, whereas a larger step length decreased the ROM of the rear knee and hip. A larger tibia angle resulted in a decreased moment in the front knee, front and rear hip and an increased moment in the rear knee. This possibility for varying the angles and corresponding moments allows coaches and therapists to adapt the lunge to an efficient exercise for strength training