Search

The agreement between a wearable inertial sensor (GYKO, G) and the force platform (P) was assessed by evaluating test-retest and inter-rater reliability. Thirty-eight subjects were enrolled; the selected indices of balance were investigated over foot positions and (un)stable conditions. Intraclass correlation coefficient (ICC), standard error of measurement (SEM%) and minimal detectable change (MDC95%) were computed. For G, ICC bounds range from poor to excellent (0.040 ÷ 0.921), mean of 0.687 (= moderate reliability). Regarding P, ICC ranges from poor to excellent (0.070 ÷ 0.920), mean of 0.683 (= moderate reliability). For G, SEM% ranges from 11% to 47%; MDC95% from 30% to 132%. Concerning P, SEM% ranges from 7% to 41%; MDC95% from 21% to 114%. Finally, the inter-rater reliability ICC by comparing devices ranges from poor to excellent (−0.162 ÷ 0.911), mean of 0.338 (= poor reliability). GYKO appears to be a convenient tool with high consistency among multiple measurements but for specific clinic/research purposes. [ABSTRACT FROM AUTHOR]

Purpose: In modern sprint cycling competitions, the athletes perform a preparatory movement that consists in reaching the backmost standing position, quickly accelerating the body forward at the starting signal. The purpose of this study was to investigate the kinematics of backward standing starts in elite cyclists, as well as the effect of initial crank angle. Methods: Video analysis of cycling starts was performed in seven male elite cyclists during 30 m sprints and in 3 starting conditions: seated with a self-selected crank angle (S-ss), backward standing from a self-selected (BSt-ss) or imposed crank angle of 90° (BSt-90°). Average velocity after 5 and 30 m was also measured by means of a photocell system. Results: No differences in starting crank angle were observed between BSt-ss and S-ss (about 64°). The fastest starts were attained in BSt-ss (highest velocity at 5 and 30 m); in this condition, angular downstroke velocity was the highest and the counter movement occurred earlier than in BSt-90°. Significant positive associations were observed between angular velocity in the first downstroke and forward velocity at 5 and 30 m. Conclusions: These findings indicate that backward standing starts improve cycling performance (compared to seated starts), that an initial crank angle < 90° is preferable, and that elite cyclists maintain the initial advantage at least up to a distance of 30 m. [ABSTRACT FROM AUTHOR]

New Findings: What is the central question of the study?Are the changes in force potentials (at the muscle level) related with metabolic changes at speeds above and below the walk‐to‐run transition?What is the main finding and its importance?The force–length and force–velocity potentials of gastrocnemius medialis during human walking decrease as a function of speed; this decrease is associated with an increase in cumulative EMG activity and in the energy cost of locomotion. Switching from fast walking to running is associated to an increase in the force potentials, supporting the idea that the 'metabolic trigger' that determines the transition from walking to running is ultimately driven by a reduction of the muscle's contractile capacity. The aim of this study was to investigate the interplay between the force–length (F–L) and force–velocity (F–V) potentials of gastrocnemius medialis (GM) muscle fascicles, the cumulative muscle activity per distance travelled (CMAPD) of the lower limb muscles (GM, vastus lateralis, biceps femori, tibialis anterior) and net energy cost (Cnet) during walking and running at speeds above and below the walk‐to‐run transition speed (walking: 2–8 km h−1; running: 6–10 km h−1). A strong association was observed between Cnet and CMAPD: both changed significantly with walking speed but were unaffected by speed in running. The F–L and F–V potentials decreased with speed in both gaits and, at 6–8 km h−1, were significantly larger in running. At low to moderate walking speeds (2–6 km h−1), the changes in GM force potentials were not associated with substantial changes in CMAPD (and Cnet), whereas at walking speeds of 7–8 km h−1, even small changes in force potentials were associated with steep increases in CMAPD (and Cnet). These data suggest that: (i) the walk to run transition could be explained by an abrupt increase in Cnet driven by an upregulation of the EMG activity (e.g., in CMAPD) at sustained walking speeds (>7 km h−1) and (ii) the reduction in the muscle's ability to produce force (e.g., in the F–L and F–V potentials) contributes to the increase in CMAPD (and Cnet). Switching to running allows regaining of high force potentials, thus limiting the increase in CMAPD (and Cnet) that would otherwise occur to sustain the increase in locomotion speed. [ABSTRACT FROM AUTHOR]

Purpose: The effects of different loads on kinematic and kinetic variables during sled towing were investigated with the aim to identify the optimal overload for this specific sprint training. Methods: Thirteen male sprinters (100-m personal best: 10.91 ± 0.14 s) performed 5 maximal trials over a 20-m distance in the following conditions: unloaded and with loads from 15% to 40% of the athlete's body mass (BM). In these calculations the sled mass and friction were taken into account. Contact and flight times, stride length, horizontal hip velocity (vh), and relative angles of hip, knee, and ankle (at touchdown and takeoff) were measured step by step. In addition, the horizontal force (Fh) and power (Ph) and maximal force (Fh0) and power (Ph0) were calculated. Results: vh, flight time, and step length decreased while contact time increased with increasing load (P < .001). These variables changed significantly also as a function of the step number (P < .01), except between the 2 last steps. No differences were observed in Fh among loads, but Fh was larger in sled towing than in unloaded. Ph was unaffected by load up to +20%BM but decreased with larger loads. Fh0 and Ph0 were achieved at 20%BM. Up to 20%BM, no significant effects on joint angles were observed at touchdown and takeoff, while at loads >30%BM joint angles tended to decrease. Conclusion: The 20%BM condition represents the optimal overload for peak power production--at this load sprinters reach their highest power without significant changes in their running technique (eg, joint angles). [ABSTRACT FROM AUTHOR]

The aim of this study was to perform a kinematic analysis of the in-run, take-off and early flight phases in water ski jumping and to analyse the differences in linear/angular parameters between males and females. Forty-two elite skiers participated in this study (27 males; 15 females); their jumps were video recorded during competitions: the time course of absolute (trunk, thigh, ski) and relative (hip, knee, ankle) angles was calculated, as well as the (trochanter) resultant speed. Males were able to reach faster in-run speeds than females (25.4 ± 1.9 and 21.8 ± 1.2 m/s, respectively) and jumped further (56.2 ± 8.6 and 40.4 ± 6.3 m). Longer jumps were correlated with faster speeds in all phases (r range: 0.87–0.91, p < 0.001, n = 42). From take-off to early flight skiers extend their hip (86–109°) and knee (136–171°) angles, lean their trunk forward (49–41°) and raise their skis (20–51°); no major sex differences were observed in the body position (or ski incline) in these phases and none of the angular parameters was correlated with jump distance. Our results suggest that skiers should focus on achieving a larger in-run speed to maximise performance in this discipline. [ABSTRACT FROM AUTHOR]

Objective: Prehospital spinal motion restriction as a prevention technique for secondary neurological injury is a key principle in emergency medicine. Our aim was to evaluate the effectiveness of different cervical spinal cord motion restriction techniques of awake and cooperative healthy volunteers during extrication. Methods: Twenty-three healthy volunteers were asked to exit a car (unassisted) with a rigid cervical collar (CC condition) or without it (autonomous exit: AE; instructed exit: IE); they were also extricated by two rescuers after setting a rigid cervical collar and by using an extrication device (CC + XT condition). Eight 3 D infrared cameras were calibrated around the vehicle to measure cervical spine angle, angular speed and acceleration in the sagittal plane. Surface wireless EMG electrodes were used to record superior trapezius, erector spinae and rectus abdominis muscle activity. All measures were recorded during two phases: device positioning (maneuver) and vehicle exiting. Results: The lowest range of motion was observed in CC during maneuver and exit (about 17°), the greatest in AE and IE (about 45°); when the extrication device was utilized along with the cervical collar (CC + XT) an increase, rather than a further decrease, in the range of motion was observed (about 25° during maneuver and exit). Larger values of angular speed and acceleration were observed in CC + XT when compared to CC, both during maneuver and exit (p < 0.001). The lowest EMG activity was observed during maneuver in CC and CC + XT; during exit a lower EMG activity was observed in CC + XT compared to CC (p < 0.001). Thus, when an extrication device is utilized (CC + XT), a lower active control of the cervical spine region is associated with faster and more brisk movements of the cervical spine compared to CC alone. Conclusions: Our findings support the idea that spinal motion restriction via rigid cervical collar of awake and cooperative trauma patients is effective in reducing cervical spine motion in the sagittal plane during vehicle extrication. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the changes in selected biomechanical variables in 80-m maximal sprint runs while imposing changes in step frequency (SF) and to investigate if these adaptations differ based on gender and training level. A total of 40 athletes (10 elite men and 10 women, 10 intermediate men and 10 women) participated in this study; they were requested to perform 5 trials at maximal running speed (RS): at the self-selected frequency (SFs) and at SF ±15% and ±30%SFs. Contact time (CT) and flight time (FT) as well as step length (SL) decreased with increasing SF, while kvert increased with it. At SFs, kleg was the lowest (a 20% decrease at ±30%SFs), while RS was the largest (a 12% decrease at ±30%SFs). Only small changes (1.5%) in maximal vertical force (Fmax) were observed as a function of SF, but maximum leg spring compression (ΔL) was largest at SFs and decreased by about 25% at ±30%SFs. Significant differences in Fmax, Δy, kleg and kvert were observed as a function of skill and gender (P < 0.001). Our results indicate that RS is optimised at SFs and that, while kvert follows the changes in SF, kleg is lowest at SFs. [ABSTRACT FROM AUTHOR]

Introduction: Parkinson's disease (PD) is a prevalent neurodegenerative condition observed primarily in the elderly population that gives rise to motor and non-motor symptoms, one of which is muscle weakness. The aim of this study was to characterize the vastus lateralis torque-fascicle length (T-L) and the knee extensors torque-angular velocity (T-V) and power-angular velocity (P-V) relationships in PD patients and to investigate the influence of muscle geometry on muscle mechanics., Methods: Participants (11 PD: patients, 9 CR: age matched healthy controls; 10 CY: young healthy controls) performed: (i) isometric contractions (e.g., MVC) to obtain the torque-angle and T-L relationships; (ii) isokinetic (e.g., iso-velocity) contractions to obtain the T-V and P-V relationships. During the experiments, the architecture of vastus lateralis (pennation angle, fascicle length, muscle thickness) was also determined by using an ultrasound apparatus., Results: Significant differences were observed between PD patients and physically matched control groups (CR and CY) in terms of maximum isometric force (calculated as the apex of the T-L curve) and maximum mechanical power (apex of the P-V curve), but not in maximum shortening velocity. Among the mechanical variables investigated, mechanical power was able to identify differences between the less and the more affected side in PD patients, suggesting that this parameter could be useful for clinical evaluation in this population., Conclusions: The observed results cannot be explained by differences in muscle geometry at rest (similar in the three cohorts), but rather by the muscle capacity to change in shape during contraction, that is impaired in PD patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Magris, Nardello, Bombieri, Monte and Zamparo.)