Biomechanics

Background/Objectives: Shaft stiffness (“flex”) is the only routinely individualised ice hockey stick specification, yet evidence on its effect on shooting is inconsistent; this is because previous studies have used fixed stiffness levels for players of different sizes and strengths. We determined the effect of deviating, in either direction, from the player’s habitual flex, congruent with the body mass reference flex, on on-ice shooting velocity and snap-shot accuracy in junior players. Methods: Thirty male junior players (18–19 years) whose habitual effective flex was within ±10 units of the body mass reference flex completed a complete counterbalanced (Williams-type) crossover with three sticks differing only in nominal shaft flex—the habitual flex (FLEX₀), a shaft 15 units more compliant (FLEX₋₁₅), and one 15 units stiffer (FLEX₊₁₅)—each preceded by three familiarisation sessions. Wrist- and snap-shot velocity (radar) and snap-shot accuracy in an externally paced target task were analysed with linear mixed models. Results: Flex affected wrist-shot velocity (ηp² = 0.35), snap-shot velocity (ηp² = 0.68) and snap-shot accuracy (ηp² = 0.34), with all three outcomes highest at FLEX₀. The wrist shot lost 2.9% with both deviations, whereas the snap shot lost 5.6% with the compliant shaft, but only 1.6% with the stiff shaft (Flex × Technique ηp² = 0.29). Snap-shot accuracy fell by 9.1 and 14.4 percentage points. Conclusions: In players fitted within ±10 units of the body mass reference flex, deviations of ±15 flex units from the habitual flex were associated with lower shooting velocity and snap-shot accuracy; for the snap shot, an over-compliant shaft was the costlier deviation.

Background: There is still a controversial debate regarding the pressure in the patellofemoral joint (PFJ) following deepening trochleoplasty (DTP). Objective: The purpose of this pilot study was to compare the PFJ contact area before and after DTP in patients treated for trochlear dysplasia and to discuss the biomechanical aspects regarding patellofemoral pressure. Methods: DTP was performed on four female patients to treat lateral patellar instability due to trochlear dysplasia. The preoperative and postoperative articular patellofemoral contact area was evaluated using three-dimensional (3D) MRI. Bone and cartilage were traced slice by slice in the acquired dimension, while the AMIRA segmentation software reconstructed the 3D model. This model was then transferred to the Rhinoceros software for measurement. Contour lines along the 3D model containing trochlear and patellar cartilage were placed, and the boundary and the curvature of the contact area were defined. The contact surfaces before and after DTP were compared. Results: The size of the articular contact area of the PFJ increased after DTP in three out of four cases compared to the preoperative condition. The preoperative average size of the contact area was 153 mm² (range, 68–185); postoperatively, it was 289 mm² (range, 200–370). The increase in contact area was, on average, 53% (−6% to 444%). Conclusions: The size of the articular contact area of the PFJ increased after DTP compared to the preoperative condition. The results provide biomechanical evidence that pressure in the PFJ decreases following DTP. The use of 3D MRI scans has demonstrated several advantages.

Background/Objectives: We investigated whether being exposed to preferred music (110–130 beats·min⁻¹) or music accelerated by 15%, played during morning exercise, influenced muscle strength and executive function assessed before and after exercise. Methods: Fourteen recreationally active males were recruited and completed seven sessions: (i) maximum (1RM) for bench press and back squat; (ii) three familiarisation sessions of strength and cognitive measures; (iii) three experimental conditions. Experimental trials were administered in a randomised counterbalanced design order of either preferred music at original tempo (MUS), preferred music accelerated by 15% (MUS15) during physical performance or no music (CON). On arrival, rectal and skin temperatures were measured alongside a battery of cognitive tests (trail making, Reys auditory verbal learning test, and Stroop word-colour interference test). Thereafter, isometric maximum voluntary contraction (MVC) with and without superimposed electrical stimulation was conducted and three repetitions were performed at 40, 60 and 80% of one repetition maximum (1RM) for bench press and back squat. Average force (AF), peak velocity (PV), time to peak velocity (tPV), and mean propulsive velocity (MPV) were recorded using MuscleLab linear encoders. The rate of perceived exertion and effort were asked after each set (RPE). Results: Music had no significant effect on MVC peak torque, % muscle activation, or key bench press and back squat outcomes. Most cognitive measures were unaffected, although time was perceived as faster during MVC (p = 0.022) on MUS. Conclusions: Music did not provide a significant acute ergogenic benefit for morning strength, power or cognitive function but may have modulated time perception.