Julie N. Cote

Integrating wearable motion sensing with neuromodulation may improve understanding of how alterations in neural excitability influence running performance and biomechanics. This study investigated whether intermittent theta burst stimulation (iTBS) applied to the primary motor cortex (M1), dorsolateral prefrontal cortex (DLPFC), or both regions influences running performance and sensor-derived spatiotemporal parameters during a 3000 m time-trial run. Ten endurance-trained runners (7 males) completed four stimulation conditions (M1, DLPFC, M1 + DLPFC, and sham) in a randomized, sham-controlled, repeated-measures crossover design. Running performance and spatiotemporal gait parameters were continuously monitored using wearable inertial measurement units (IMUs), with analyses conducted across the initial, steady-state, and final acceleration phases of the run. The M1 + DLPFC condition resulted in the fastest mean completion time, averaging approximately three seconds faster than sham. However, these differences were not statistically significant. Sensor-derived biomechanical measures revealed significantly higher running speeds and alterations in stride time and step frequency during the initial phase following combined stimulation compared with the other conditions. Ratings of perceived exertion and spatiotemporal variability did not differ between stimulation conditions. These findings demonstrate the utility of wearable IMUs for detecting subtle phase-specific changes in running biomechanics and suggest that combined stimulation of motor and cognitive control regions may influence early-stage running performance, warranting further investigation in larger cohorts. As the complete sample consisted of only ten runners, these findings are preliminary and require confirmation in a larger sample size.

The basal ganglia contribute to internal timekeeping, and dopaminergic medication has been observed to moderate timing deficits associated with Parkinson’s Disease (PD) during single joint movements. However, it is unclear whether similar effects can be observed in multi-joint movements. Twenty-five people with PD and twelve healthy peers performed repetitive reaching and stepping-in-place tasks with and without auditory cues at their self-selected maximal cadence. The PD group was measured ON and OFF medication. Reduced cadence error was found for both groups and tasks when cued, and ON PD exhibited decreased cadence compared to OFF PD. Overall timing variability was no different from controls, but differences were found in estimates of clock and motor variance using the Wing-Kristofferson model of interval timing. A medication and cueing interaction during the reaching task produced increased clock variance in uncued, ON PD. During the stepping task, clock and motor variance of the PD group were unaffected by cues, in contrast to the control group. Serial lag-one correlation was reduced in both groups for cued reaching, but was unaffected by cueing or medication in the PD group when stepping-in-place. These findings suggest that overall timing variability may not capture timing deficits in PD.

Performance in short-track speed skating is driven by technique optimization. However, because of discomfort, clutter or complexity, regular instrumentation may not be suitable for use in daily training. The objective of this study was to validate a single-accelerometer-based algorithm 1) to detect the number of strokes and 2) accurately classify left, right, pivot, and straightline strokes during 4-lap and 9-lap practice race simulations. Twenty-eight athletes from the Canadian National Short-Track Speed-Skating Team were instrumented with an accelerometer taped to their sacrums that would collect tridimensional accelerations and angles from start to finish, and they were filmed with a single camera setup during 4-lap and/or 9-lap individual race trials. Data were analyzed with a custom Matlab algorithm and compared to video data on two datasets to investigate the number of strokes, pivots, and straights detected. Over 98% of strokes were detected; and over 99% right/left strokes, 97.7 % pivots, and 98.6% straights were identified. The validation led to intra-class correlation coefficients (ICC(3,1)) of over 0.97, indicating an excellent agreement between the two methods. The results support the ability of wearable technology to deliver valid speed-skating data, enabling rapid feedback to coaches and athletes with minimal equipment in training.

Females demonstrate greater fatigue resistance during a range of exercise modalities; however, this may be confounded by the lower mechanical work completed. Accordingly, this study examined the sex-specific peripheral and central fatigue mechanisms during repeated all-out cycling and whether they are affected by total mechanical work performed. A total of 26 healthy young adults (12 females) performed 10 × 10 s all-out cycling interspersed by 30 s passive recovery. Metabolic responses, peripheral and central fatigue, were quantified via changes in pre- to post-exercise blood lactate, potentiated quadriceps twitch force (and contractile properties) evoked via supramaximal electrical stimulation of the femoral nerve, and voluntary activation of the knee extensors, respectively. During exercise, mechanical work, vastus lateralis muscle activation (via surface electromyography), and deoxygenation (via near-infrared spectroscopy) were recorded. Sex comparison analyses were performed before and after statistically controlling for total mechanical work (via ANCOVA). Mechanical work and muscle activation plateaued at similar sprint repetition (sprint 5) and voluntary activation change (pre vs. post) was similar between the sexes. Females, however, showed lower %work decrement (i.e., fatigability; P = 0.037) and peripheral responses as evident by lower reductions in quadriceps twitch force ( P < 0.001) and muscle deoxygenation ( P = 0.001). Adjusting for total mechanical work did not change these sex comparison results. We show that females’ greater fatigue resistance during repeated all-out cycling may not be attributed to the greater total mechanical work performed but could be mediated by lower peripheral fatigue in the knee extensor muscles.

Biomechanics and training load monitoring are important for performance evaluation and injury prevention in elite swimming. Monitoring of performance and swim stroke parameters is possible with inertial measurement units (IMU) but has not been validated in para-swimmers. The purpose of this study was to validate a single IMU-based system to accurately estimate pool-swam lap time, stroke count (SC), stroke duration, instantaneous stroke rate (ISR), and distance per stroke (DPS). Eight Paralympic athletes completed 4 × 50 m swims with an IMU worn on the sacrum. Strokes cycles were identified using a zero-crossing algorithm on the medio-lateral (freestyle and backstroke) or forward-backward (butterfly and breaststroke) instantaneous velocity data. Video-derived metrics were estimated using Dartfish and Kinovea. Agreement analyses, including Bland–Altman and Intraclass Correlation Coefficient (ICC), were performed on all outcome variables. SC Bland–Altman bias was 0.13 strokes, and ICC was 0.97. ISR Bland–Altman biases were within 1.5 strokes/min, and ICCs ranged from 0.26 to 0.96. DPS Bland–Altman biases were within 0.20 m, and ICCs ranged from 0.39 to 0.93. A single-IMU system can provide highly valid performance and swim stroke monitoring data for elite para-swimmers for the majority of strokes, with the exception of backstroke. Future work should improve bilateral stroke detection algorithms in this population.

Introduction: An imbalance of vastus medialis (VM) and vastus lateralis (VL) muscle activation and patterns of dyscoordination may contribute to the sex discrepancy in the incidence of patellofemoral pain syndrome (PFPS). While some studies have examined sex-specific VM/VL coordination strategies in some tasks, no previous studies have examined sex-specific VM/VL coordination strategies during repeated sprint exercise (RSE).Methods: In this study, asymptomatic young adults (N = 39, 19 females) completed a RSE protocol consisting of 10 × 10 s all-out cycling interspersed by 30 s of passive rest. Electromyographic (EMG) signals from the VM and VL muscles were recorded throughout exercise.Results: VM:VL ratio did not change with fatigue and was not different between the sexes. From sprint 1 to 10, VM-VL onset delay increased from 9.62 to 16.95 ms and from 19.28 to 45.09 ms in males and females, respectively (p < 0.001); however, no sex difference was found (p = 0.524). Muscle activation amplitude plateaued at different sprint repetitions in males and females while mechanical work plateaued at similar repetitions.Discussion: These findings suggest that sex differences in the incidence of PFPS may not be influenced by VM/VL muscle coordination as assessed by EMG.