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Background: Recommendations for the alignment of the socket and foot in the sprinting prosthesis of athletes with transfemoral amputation are either based on walking biomechanics or lack public scientific evidence.Objectives: To explore the biomechanical changes and the sensations of a gold medal Paralympic sprinter, while running with three bench alignments: a conventional reference (A0), an innovative alignment based on the biomechanics of elite able-bodied sprinters (A2), and an intermediate alignment (A1).Study design: Single subject with repeated measures.Methods: A1 and A2 feature a progressively greater socket tilt and a plantar-flexed foot compared to A0. The 30-year-old female athlete trained with three prostheses, one per alignment, for at least 2 months. We administered a questionnaire to collect her impressions. Then, she ran on a treadmill at full speed (5.5 m/s). We measured the kinematics and moments of the prosthetic side, and the ground reaction forces of both sides.Results: A2 reduced the prosthetic side hip extension at foot-off while preserving hip range of motion, decreased the impulse of the hip moment, and increased the horizontal propulsion, leaving sufficient margin to prevent knee buckling without increasing sound side braking forces. Biomechanical outcomes matched well with subjective impressions.Conclusions: A2 appears promising to improve the performance and comfort of sprinters with transfemoral amputation, without compromising safety.Clinical relevance bservation of elite able-bodied sprinters led to the definition of a new specific alignment for the sprinting prosthesis of athletes with transfemoral amputation, which appears promising to improve performance and comfort, without compromising safety. This may constitute a major improvement compared to alignments based on walking biomechanics.

In cycling, non-traumatic injuries affecting the genitourinary tract have been the most extensively studied considering their effect in reducing the quality of life. The employment of saddle with specific geometries and of cycling shorts with pads can contribute to reduce the pressure on the perineal area and to increase the level of comfort. The aim of this study was to develop a method to quantify the mechanical properties of pads which can influence the cyclist’s perineal protection and its level of comfort. The proposed method consisted of both a laboratory and a field test component. The laboratory part included an accelerated fatigue test of 300,000 cycles performed with an hydraulic actuator. Loads employed were derived from pressure data collected on the saddle of a professional cyclist who pedalled both on asphalt and crossing potholes at a constant speed. The measurement of cylinder force and displacement allowed to calculate the damping and the stiffness over time for the pads tested. The field test allowed to collect the acceleration at the seatpost of the bike and at the back of the cyclist by means of two accelerometers. A transfer function (H(f))allowed to quantify the vibration transmissibility of the pads. The application of our method characterized the pads tested concerning damping, stiffness and vibration transmissibility. This method could be useful for the manufacturer in the choice of density and thickness of foams, to obtain the desired level of protection, comfort and long-time efficacy of pads.

Context: The push-up is a widely used exercise for upper limb strengthening that can be performed with many variants. A comprehensive analysis of muscle activation during the ascendant phase (AP) and descendant phase (DP) in different variants could be useful for trainers and rehabilitators.Objective: To obtain information on the effect of different push-up variants on the electromyography (EMG) of a large sample of upper limb muscles and to investigate the role of the trunk and abdomen muscles during the AP and DP.Design: Cross-sectional study.Setting: University laboratory.Patients or Other Participants: Eight healthy, young volunteers without a history of upper extremity or spine injury.Intervention(s): Participants performed a set of 10 repetitions for each push-up variant: standard, wide, narrow, forward (FP), and backward (BP). Surface EMG of 12 selected muscles and kinematics data were synchronously recorded to describe the AP and DP.Main Outcome Measure(s): Mean EMG activity of the following muscles was analyzed: serratus anterior, deltoideus anterior, erector spinae, latissimus dorsi, rectus abdominis, triceps brachii caput longus, triceps brachii caput lateralis, obliquus externus abdominis, pectoralis major sternal head, pectoralis major clavicular head, trapezius transversalis, and biceps brachii.Results: The triceps brachii and pectoralis major exhibited greater activation during the narrow-base variant. The highest activation of abdomen and back muscles was recorded for the FP and BP variants. The DP demonstrated the least electrical activity across all muscles, with less marked differences for the abdominal and erector spinae muscles because of their role as stabilizers.Conclusions: Based on these findings, we suggest the narrow-base variant to emphasize triceps and pectoralis activity and the BP variant for total upper body strength conditioning. The FP and BP variants should be implemented carefully in participants with low back pain because of the greater activation of abdominal and back muscles.

In outdoor footwear, sole properties must guarantee grip with the ground and support the forefoot without altering the kinematics of the metatarsophalangeal joints (MPJ). The present study aimed to implement an objective measure of shoe bending stiffness and investigate the effect of shoes with different bending stiffness on MPJ kinematics, kinetics, and energy balance during walking. The bending stiffness of four shoes was calculated using a customized flexometer. Then, the influence of each footwear on MPJ biomechanics during level and uphill walking was investigated with a motion capture system and a force plate on 10 healthy subjects. Results showed that MPJ peak dorsiflexion angle, stiffness, and energy balance were affected both by shoe bending stiffness (p<0.001) and walking slope (p<0.001). The findings of the study, which quantify the influence of shoe stiffness on MPJ biomechanics, will be helpful in the design of outdoor footwear.