Predicting cumulative load during running using field-based measures.

The main objective was to investigate whether the cumulative load of the lower limbs, defined as the product of external load and step rate, could be predicted using spatiotemporal variables gathered with a commercially available wearable device in running. Therefore, thirty-nine runners performed two running tests at 10 and 12 km/h, respectively. Spatiotemporal variables (step rate, ground contact time, and vertical oscillation) were collected using a commercially available wearable device. Kinetic variables, measured with gold standard equipment (motion capture system and instrumented treadmill) and used for the calculation of a set of variables representing cumulative load, were peak vertical ground reaction force (peak vGRF), vertical instantaneous loading rate (VILR), vertical impulse, braking impulse, as well as peak extension moments and angular impulses of the ankle, knee and hip joints. Separate linear mixed-effects models were built to investigate the prediction performance of the spatiotemporal variables for each measure of cumulative load. BMI, speed, and sex were included as covariates. Predictive precision of the models ranged from .11 to .66 (R2 m ) and .22 to .98 (R2 c ), respectively. Greatest predictive performance was obtained for the cumulative peak vGRF (R2 m  = .66, R2 c  = .97), VILR (R2 m  = .43, R2 c  = .97), braking impulse (R2 m  = .52, R2 c  = .98), and peak hip extension moment (R2 m  = .54, R2 c  = .90). In conclusion, certain variables representing cumulative load of the lower limbs in running can be predicted using spatiotemporal variables gathered with a commercially available wearable device.

Running in circles: Describing running kinematics using Fourier series.

We explore the use of Fourier series to describe the kinematics of human running. From a database of 285 trials of treadmill running, we drive a musculoskeletal model with 104 anatomical joint angles to obtain kinematics. Using FFT analysis, we determine a fundamental frequency for all independent joint angles and compute average step kinematics. Finally, we represent the average step kinematics using Fourier series with numbers of coefficient pairs ranging from one through ten. We find that five or fewer Fourier coefficient pairs provide an accurate (Pearson's correlation > 0.99 and root mean square difference < 0.5 degrees) representation for most joint angles. In conclusion, Fourier series appear to provide a compact and valid representation of running kinematics, thus enabling researchers to confidently use Fourier series in research of human running.

Quantifying throwing load in handball: a method for measuring the number of throws.

Shoulder injuries are a common problem in handball. One likely cause of such injuries is excessive throwing. However, it is difficult to measure the number of player throws in large cohort studies using existing methods accurately. Therefore, the purpose of this study is to develop and validate a method for identifying overhead throws using a low-cost inertial measurement unit (IMU) worn on the wrist. In a two-stage approach, we developed a threshold-based automatic identification method for overhead throws in a laboratory study using the IMU. Subsequently, we validated the suggested thresholds in a field setting by comparing throws identified by the threshold-method to throws identified by video recordings of handball practices. The best set of threshold values resulted in a per-player median sensitivity of 100% (range: 84-100%) and a median positive predictive value (PPV) of 96% (range: 86-100%) in the development study. In the validation study, the per-player median sensitivity dropped to 78% sensitivity (range: 52-91%), while the per-player median PPV dropped to 79% (range: 47-90%). The proposed method is a promising method for automatically identifying handball throws in a cheap and feasible way.

Shoulder kinematics and kinetics of team handball throwing: A scoping review.

In recent years a number of studies have investigated shoulder biomechanics in handball throwing. The purpose of this scoping review is to summarize the current handball research in terms of shoulder joint kinematics and kinetics and identify gaps in the current research. Nineteen articles relevant to this topic were identified and included. The handball throw is characterized by large external shoulder rotation followed by a rapid internal rotation with minor changes in shoulder flexion and abduction. Generally timing sequence, joint angles and joint velocities were not affected by different conditions such as throwing type, arm position, ball weight and gender. However, large differences in shoulder angles and angular velocities were found between studies, which most likely are explained by methodological differences. Unfortunately, the information provided in the articles did not make it possible to transform measurements from one study to another and thereby eliminate the methodological differences. Only one study reported shoulder kinetics and found that kinetics were not affected by fatigue. This scoping review highlights the need for better descriptions of the methods used to obtain shoulder kinematics and for studies investigating shoulder kinetics in handball throwing.