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Inertial Sensor-Based Estimation of Temporal Events in Skating Sub-Techniques While In-Field Roller Skiing

Frédéric Meyer, Magne Lund-Hansen, Jan Kocbach, Trine M. Seeberg, Øyvind B. Sandbakk, and Andreas Austeng

The aim of this study was to test and adapt a treadmill-developed method for determination of inner-cycle parameters and sub-technique in cross-country roller ski skating for a field application. The method is based on detecting initial and final ground contact of poles and skis during cyclic movements. Eleven athletes skied 4 laps of 2.5 km at low- and high-endurance intensities, using 2 types of skis with different rolling coefficients. Participants were equipped with inertial measurement units attached to their wrists and skis, and insoles with pressure sensors and poles with force measurements were used as reference systems. The method based on inertial measurement units was able to detect >97% of the temporal events detected with the reference system. The inner-cycle temporal parameters had a precision ranging from 49 to 59 milliseconds, corresponding to 3.9% to 13.7% of the corresponding inner-cycle duration. Overall, this study showed good reliability of using inertial measurement units on athletes’ wrists and skis to determine temporal events, inner-cycle parameters, and the performed sub-techniques in cross-country roller ski skating in field conditions.

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Effects of Visual Input Absence on Balance Recovery Responses to Lateral Standing Surface Perturbations in Older and Younger Adults

Woohyoung Jeon, James Borrelli, and Hao-Yuan Hsiao

Although the ability to recover balance in the lateral direction has important implications with regard to fall risk in older adults, the effect of visual input on balance recovery in response to lateral perturbation and the effect of age are not well studied. We investigated the effect of visual input on balance recovery response to unpredictable lateral surface perturbations and its age-related changes. Ten younger and 10 older healthy adults were compared during balance recovery trials performed with the eyes open and eyes closed (EC). Compared with younger adults, older adults showed increased electromyography (EMG) peak amplitude of the soleus and gluteus medius, reduced EMG burst duration of the gluteus maximus and medius, and increased body sway (SD of the body’s center of mass acceleration) in EC. In addition, older adults exhibited a smaller % increase (EC—eyes open) of the ankle eversion angle, hip abduction torque, EMG burst duration of the fibularis longus, and a greater % increase of body sway. All kinematics, kinetics, and EMG variables were greater in EC compared with eyes open in both groups. In conclusion, the absence of visual input negatively affects the balance recovery mechanism more in older adults compared with younger adults.

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Joint Coordination With a Change in Task Constraint During Accurate Overhead Throwing

Arata Kimura, Shinsuke Yoshioka, and Senshi Fukashiro

In sports situations, players may be required to throw at different speeds. The question of how skilled players throw the ball accurately to the desired location under different speed conditions is of interest to biomechanics researchers. Previous research suggested that throwers use different types of joint coordination. However, joint coordination with a change in throwing speed has not been studied. Here, we show the effects of changes in throwing speed on joint coordination during accurate overhead throwing. Participants were seated on a low chair with their trunk fixed and threw a baseball aimed at a target under 2 different speed conditions (slow and fast). In the slow condition, the elbow flexion/extension angle coordinated with other joint angles and angular velocities to reduce the variability of the vertical hand velocity. In the fast condition, the shoulder internal/external rotation angle and the shoulder horizontal flexion/extension angular velocity coordinated with other joint angles and angular velocities to reduce the variability of the vertical hand velocity. These results showed that joint coordination differed with changes in throwing speed, indicating that joint coordination is not always fixed, but may differ depending on the task constraints, such as throwing speed.

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Characterization of Head Acceleration Exposure During Youth Football Practice Drills

Ty D. Holcomb, Madison E. Marks, N. Stewart Pritchard, Logan Miller, Mark A. Espeland, Christopher M. Miles, Justin B. Moore, Kristie L. Foley, Joel D. Stitzel, and Jillian E. Urban

Many head acceleration events (HAEs) observed in youth football emanate from a practice environment. This study aimed to evaluate HAEs in youth football practice drills using a mouthpiece-based sensor, differentiating between inertial and direct HAEs. Head acceleration data were collected from athletes participating on 2 youth football teams (ages 11–13 y) using an instrumented mouthpiece-based sensor during all practice sessions in a single season. Video was recorded and analyzed to verify and assign HAEs to specific practice drill characteristics, including drill intensity, drill classification, and drill type. HAEs were quantified in terms of HAEs per athlete per minute and peak linear and rotational acceleration and rotational velocity. Mixed-effects models were used to evaluate the differences in kinematics, and generalized linear models were used to assess differences in HAE frequency between drill categories. A total of 3237 HAEs were verified and evaluated from 29 football athletes enrolled in this study. Head kinematics varied significantly between drill categorizations. HAEs collected at higher intensities resulted in significantly greater kinematics than lower-intensity drills. The results of this study add to the growing body of evidence informing evidence-based strategies to reduce head impact exposure and concussion risk in youth football practices.

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The Effect of Sensor Placement on Measured Distal Tibial Accelerations During Running

Lauren K. Sara, Jereme Outerleys, and Caleb D. Johnson

Inertial measurement units (IMUs) attached to the distal tibia are a validated method of measuring lower-extremity impact accelerations, called tibial accelerations (TAs), in runners. However, no studies have investigated the effects of small errors in IMU placement, which would be expected in real-world, autonomous use of IMUs. The purpose of this study was to evaluate the effect of a small proximal shift in IMU location on mean TAs and relationships between TAs and ground reaction force loading rates. IMUs were strapped to 18 injury-free runners at a specified standard location (∼1 cm proximal to medial malleolus) and 2 cm proximal to the standard location. TAs and ground reaction forces were measured while participants ran at self-selected and 10% slower/faster speeds. Mean TA was lower at the standard versus proximal IMU location in the faster running condition (P = .026), but similar in the slower (P = .643) and self-selected conditions (P = .654). Mean TAs measured at the standard IMU explained more variation in ground reaction force loading rates (r 2 = .79−.90; P < .001) compared with those measured at the proximal IMU (r 2 = .65−.72; P < .001). These results suggest that careful attention should be given to IMU placement when measuring TAs during running.

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The Effects of Posture and Dynamic Stretching on the Electromechanical Delay of the Paraspinal Muscles

Richard O. Fagbemigun, Melissa Cavallo, and Stephen H.M. Brown

Electromechanical delay (EMD) of muscle is influenced in part by its in-series arrangement with connective tissue. Therefore, studying EMD might provide a better understanding of the muscle–connective tissue interaction. Here, EMD of the thoracic and lumbar erector spinae muscles were investigated under conditions that could influence muscle–connective tissue interaction. A total of 19 participants performed isometric back extension contractions in 3 different postures that influence lumbar spine angle: sitting, standing, and kneeling. They then performed a 15-minute dynamic stretching routine and repeated the standing contractions. Mean lumbar flexion angles of 0.5°, 9.9°, and 19.8° were adopted for standing, kneeling, and sitting, respectively. No statistically significant differences in the thoracic erector spinae EMD were found between the different postures. Lumbar erector spinae EMD was significantly longer in the sitting (94.1 ms) compared to the standing (69.9 ms) condition, with no differences compared to kneeling (79.7 ms). There were no statistically significant differences of the thoracic or lumbar erector spinae EMDs before and after dynamic stretching. These results suggest that dynamic stretching does not affect the mechanical behavior of the muscle-tendon–aponeurosis units in a way that alters force generation and transmission, but a sitting posture can alter how force is transmitted through the musculotendinous complex of the lumbar erector spinae.

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Lower Extremity Inverse Kinematics Results Differ Between Inertial Measurement Unit- and Marker-Derived Gait Data

Jocelyn F. Hafer, Julien A. Mihy, Andrew Hunt, Ronald F. Zernicke, and Russell T. Johnson

In-lab, marker-based gait analyses may not represent real-world gait. Real-world gait analyses may be feasible using inertial measurement units (IMUs) in combination with open-source data processing pipelines (OpenSense). Before using OpenSense to study real-world gait, we must determine whether these methods estimate joint kinematics similarly to traditional marker-based motion capture (MoCap) and differentiate groups with clinically different gait mechanics. Healthy young and older adults and older adults with knee osteoarthritis completed this study. We captured MoCap and IMU data during overground walking at 2 speeds. MoCap and IMU kinematics were computed with OpenSim workflows. We tested whether sagittal kinematics differed between MoCap and IMU, whether tools detected between-group differences similarly, and whether kinematics differed between tools by speed. MoCap showed more anterior pelvic tilt (0%–100% stride) and joint flexion than IMU (hip: 0%–38% and 61%–100% stride; knee: 0%–38%, 58%–89%, and 95%–99% stride; and ankle: 6%–99% stride). There were no significant tool-by-group interactions. We found significant tool-by-speed interactions for all angles. While MoCap- and IMU-derived kinematics differed, the lack of tool-by-group interactions suggests consistent tracking across clinical cohorts. Results of the current study suggest that IMU-derived kinematics with OpenSense may enable reliable evaluation of gait in real-world settings.

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Volume 39 (2023): Issue 2 (Apr 2023)

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Mechanisms of Anterior Cruciate Ligament Tears in Professional National Basketball Association Players: A Video Analysis

Adam J. Petway, Matthew J. Jordan, Scott Epsley, Philip Anloague, and Ernest Rimer

A systematic search was performed of online databases for any anterior cruciate ligament (ACL) injuries within the NBA. Video was obtained of injuries occurring during competition and downloaded for 2-dimensional video analysis. Thirty-five in-game videos were obtained for analysis. Of the reviewed cases, 19% were noncontact ACL injuries where there was no player-to-player contact from an opposing player. Three injury mechanism categories were found based on the events at the point of initial ground contact of the foot of the injured limb: single-leg casting (mean dorsiflexion angle 18.9° (14.4°); mean knee flexion angle 15.6° (7.8°); and mean trunk lateral flexion 18.2° (8.4°)); bilateral hop (mean dorsiflexion angle 18.2° (15.2°), mean knee flexion angle 21° (14.5°), mean trunk extension angle 6.9° (11.4°), and landing angle from the athlete’s center of mass 47.9° (10.1°)); and single-leg landing after contact (mean abduction angle of the swing leg 105.4° (18.1°), mean knee flexion angle of the injured limb 34.2° (8.0°), and mean trunk ipsilateral flexion angle 22.2° (7.0°)).

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Minimum Sampling Frequency for Accurate and Reliable Tibial Acceleration Measurements During Rearfoot Strike Running in the Field

Kevin G. Aubol and Clare E. Milner

Field-based tibial acceleration measurements are increasingly common but sampling frequencies vary between accelerometers. The purpose of this study was to determine the minimum sampling frequency needed for reliable and accurate measurement of peak axial and resultant tibial acceleration during running in the field. Tibial acceleration was measured at 7161 Hz in 19 healthy runners on concrete and grass. Acceleration data were down sampled to approximate previously used sampling frequencies. Peak axial and resultant tibial acceleration were calculated for each sampling frequency. The within-session reliability and accuracy of peak axial and resultant tibial accelerations were evaluated using intraclass correlation coefficients, mean differences, and 95% limits of agreements. Intraclass correlation coefficients greater than .9 indicated excellent within-session reliability for both peak axial and resultant tibial acceleration measured while running on concrete and grass. Peak axial and resultant tibial accelerations were 0.5 to 1.4 g lower and minimal detectable differences were up to 0.6 g higher at 102 Hz compared with higher sampling frequencies. We recommend a minimum sampling frequency of 199 Hz for accurate and reliable measurements of peak axial and resultant tibial acceleration in the field.