The Soft Prefabricated Orthopedic Insole Decreases Plantar Pressure during Uphill Walking with Heavy Load Carriage.

This study aimed to investigate the effect of varying the hardness of prefabricated orthopedic insoles on plantar pressure and muscle fatigue during uphill walking with a heavy backpack. Fifteen healthy male recreational athletes (age: 20.4 ± 1.0 years, height: 176.9 ± 5.7 cm, weight: 76.5 ± 9.0 kg) wore prefabricated orthopedic insoles with foot arch support; a heel cup with medium (MI), hard (HI), and soft (SI) relative hardnesses; and flat insoles (FI). They performed treadmill walking on uphill gradients with 25 kg backpacks. The plantar pressure and surface electromyographic activity were recorded separately, in 30 s and 6 min uphill treadmill walking trials, respectively. The HI, MI, and SI significantly decreased peak plantar pressure in the lateral heel compared to FI. The MI and SI significantly decreased the peak plantar pressure in the fifth metatarsal compared to FI. The MI significantly reduced the pressure-time integral in the lateral heel compared to FI. The HI significantly increased the peak plantar pressure and pressure-time integral in the toes compared to other insoles, and decreased the contact area in the metatarsal compared to SI. In conclusion, a prefabricated orthopedic insole made of soft material at the fore- and rearfoot, with midfoot arch support and a heel cup, may augment the advantages of plantar pressure distribution during uphill weighted walking.

Classification of Plank Techniques Using Wearable Sensors.

The plank is a common core-stability exercise. Developing a wearable inertial sensor system for distinguishing between acceptable and aberrant plank techniques and detecting specific deviations from acceptable plank techniques can enhance performance and prevent injury. The purpose of this study was to develop an inertial measurement unit (IMU)-based plank technique quantification system. Nineteen healthy volunteers (age: 20.5 ± 0.8 years, BMI: 22.9 ± 1.4 kg/m2) performed the standard plank technique and six deviations with five IMUs positioned on the occiput, cervical spine, thoracic spine, sacrum, and right radius to record movements. The random forest method was employed to perform the classification. The proposed binary tree classification model achieved an accuracy of more than 86%. The average sensitivities were higher than 90%, and the specificities were higher than 91%, except for one deviation (83%). These results suggest that the five IMU-based systems can classify the plank technique as acceptable or aberrant with good accuracy, high sensitivity, and acceptable specificity, which has significant implications in monitoring plank biomechanics and enabling coaching practice.

Effects of attaching elastic bands to the waist and heels on drop jumps.

This study aimed to investigate the effects of the external load of elastic bands attached to the waist and heels to enhance the pre-activation of leg extensor muscles on drop jumps (DJs). Twelve male college athletes volunteered for this study. Eight cameras and two force platforms were used to collect data. Each subject performed DJs with elastic band loads of 0% and 20% body weight (BW) attached to the waist and heels during the airborne and landing phases from 40- and 50-cm drop heights. Repeated measures of two-way analysis of variance were performed with two loads of the elastic bands and two heights of the platform for each dependent biomechanical variable. Jump height, reactive strength index, leg stiffness, hip, knee flexion, and ankle plantarflexion angles at the initial foot contact and ankle dorsiflexion range of motion (ROM) significantly increased with 20% BW loads. The peak ground reaction force of impact, eccentric work, and hip flexion range of motion significantly decreased with 20% BW loads. The use of the elastic bands as accentuated loading during the airborne and landing phases of DJs can induce pre-activation of the joint extensors of the lower extremity to achieve stretch-shortening cycle benefits and performance and reduce the ground impact for the lower extremity. HighlightsAttaching elastic bands to the waist and heels enables the following during drop jumps.The joint extensors of the lower extremities act as a counterbalance to the pull from the elastic bands.The performance of the drop jump was improved.The ground impact was reduced.

The Acute Effect of Foam Rolling and Vibration Foam Rolling on Drop Jump Performance.

The purpose of this study was to examine the acute effect of foam rolling and vibration foam rolling on drop jump performance. The optimal time interval between warm-up using foam rolling or vibration foam rolling and drop jump performance was identified. This study included 16 male NCAA Division I college volleyball athletes. Three interventions were performed in a randomized order: the foam rolling exercise (FRE), vibration foam rolling exercise (VFRE), and static rest (control). The drop jump was performed before interventions, as well as 2 and 5 min after interventions. The FRE exhibited higher values for drop jump height (DJH) (p = 0.001; η2 = 0.382; statistical power = 0.964) and mean power generation at the hip joint (p = 0.006; η2 = 0.277; statistical power = 0.857) at 2 min compared with before intervention but not at 5 min (p > 0.05). However, the VFRE showed no significant changes in DJH (p > 0.05), and found that hippower was decreased at 5 min (p = 0.027; η2 = 0.214; statistical power = 0.680). The FRE completed in 2 min before rapid single action competition (sprint, long jump, triple jump, etc.) could increase sports performance.

Acute Effects of Squats Using Elastic Bands on Postactivation Potentiation.

ABSTRACT: Peng, H-T, Zhan, D-W, Song, C-Y, Chen, Z-R, Gu, C-Y, Wang, I-L, and Wang, L-I. Acute effects of squats using elastic bands on postactivation potentiation. J Strength Cond Res 35(12): 3334-3340, 2021-The study aimed to investigate the acute effects of squats using elastic bands at different resistance and recovery time points on postactivation potentiation (PAP). Fifteen male collegiate physical education students volunteered to participate in the study. Subjects were assigned to 6 experimental visits, which consisted of repeated factors that were 2 resistance squats (3 repetition maximum [RM] and 5RM) with elastic bands as intervention and 3 performance tests (countermovement jumps [CMJs], 20-m sprints, and change of direction [COD]). The performance test was measured before the resistance squat (pre-test) and at 15 seconds, 4 minutes, and 8 minutes after the resistance squat (post-tests) on each visit. An AMTI force plate and a set of Optojump sensors were used to obtain ground reaction force data during the CMJs and during the 20-m sprints and COD test, respectively. Repeated-measures two-way analyses of variance were performed for the resistance squats and recovery time points for each dependent variable. The 20-m sprint and COD test times at the 4-minute recovery time point after 3RM and 5RM resistance squatting were shorter than the pre-test values (p < 0.05). The rates of force development at the 4- and 8-minute recovery time points after 5RM resistance squatting were higher than the corresponding pre-test values (p < 0.05). All test performance variables significantly decreased at the 15-second recovery time point (p < 0.05). The use of elastic bands in 3RM and 5RM resistance squatting as a warm-up activity may positively affect PAP to improve sprinting, COD ability, and jump explosiveness at the 4-minute recovery time point.

The arch support insoles show benefits to people with flatfoot on stance time, cadence, plantar pressure and contact area.

BACKGROUND: Pes planus (flatfoot) is a common deformity characterized by the midfoot arch collapses during walking. As the midfoot is responsible for shock absorption, persons with flatfoot experience increased risk of injuries such as thumb valgus, tendinitis, plantar fasciitis, metatarsal pain, knee pain, lower-back pain with prolonged uphill, downhill, and level walking, depriving them of the physical and mental health benefits of walking as an exercise. METHODS: Fifteen female college students with flatfoot were recruited. A wireless plantar-pressure system was used to measure the stance time, cadence, plantar pressure, and contact area. Parameters were compared between wearing flat and arch-support insoles using a two-way repeated measures ANOVA with on an incline, decline, and level surface, respectively. The significance level α was set to 0.05. The effect size (ES) was calculated as a measure of the practical relevance of the significance using Cohen's d. RESULTS: On the level surface, the stance time in the arch-support insole was significantly shorter than in the flat insole (p<0.05; ES = 0.48). The peak pressure of the big toe in the arch-support insole was significantly greater than in the flat insole on the uphill (p<0.05; ES = 0.53) and level surfaces (p<0.05; ES = 0.71). The peak pressure of the metatarsals 2-4 and the contact area of the midfoot in the arch-support insole were significantly greater than in the flat insole on all surfaces (all p< 0.05). CONCLUSIONS: These results imply that wearing an arch-support insole provides benefits in the shortened stance time and generation of propulsion force to the big toe while walking on uphill and level surfaces and to the metatarsals 2-4 while walking on the level surface. More evenly distributed contact areas across the midfoot may help absorb shock during uphill, downhill and level walking.

Differences Between Bimodal and Unimodal Force-time Curves During Countermovement Jump.

This study aimed to explore the biomechanical differences between single and double peak ground reaction force-time curves during the countermovement jump with respect to kinematics, kinetics, and coordination of the lower extremities. Twenty-five college students were stratified into a single peak curve group and a double peak curve group. Eight infrared cameras and two force platforms were synchronized to collect the data. Independent t-tests were performed with groups for each dependent kinematic, kinetic and time of the joint extensor concentric contraction variable. Repeated one-way analysis of variance measurements were performed for the time of the ankle, knee and hip extensor concentric contraction in each group. The double peak curve was associated with larger jump height, reactive strength index modified, rate of force development, impulse, hip, knee and ankle flexion, extension angular displacement, and hip and knee moments (p<0.05). The double peak curve group revealed a better hip, knee and ankle (proximal to distal) timing of extensor concentric contractions sequence of the lower extremities during the countermovement jump (p<0.05). The double peak curve group exhibited a more effective countermovement jump movement with respect to biomechanics compared to the single peak curve group.

Can Different Complex Training Improve the Individual Phenomenon of Post-Activation Potentiation?

The aims of the present study were (a) to determine whether the two types of complex training and vibration complex training would improve the individual phenomenon of post-activation potentiation (PAP) for every athlete in a team setting; and (b) to compare the acute effect of resistance and plyometric exercise, whole body vibration, complex training and vibration complex training on vertical jump performance. The participants were ten male division I college volleyball and basketball players. They were asked to perform three vertical jumps as a pre-test and were then randomly assigned to one of five PAP protocols, resistance exercise using half squat exercise, plyometric exercise using drop jumps with individualized drop height, whole body vibration using squats on a vibration plate, complex training combining resistance exercise with plyometric exercise, vibration complex training combining whole body vibration with plyometric exercise. Three vertical jumps were performed four minutes after the PAP protocol as a post-test. A two-way repeated-measures analysis of variance was used to examine the differences among the five PAP protocols and between the two testing times. Our results showed that the post-test results were significantly improved compared to the pre-test for the vertical jump height (p = .015) in all PAP protocols. There was, however, an individual phenomenon of PAP in the response to all PAP protocols. In conclusion, this study found that resistance and plyometric exercise, whole body vibration, complex training and vibration complex training induce similar group PAP benefits. However, some athletes decreased their performances in some of the exercises in the study. Therefore, it is not recommended for coaches to arrange the exercises in a team setting.

Whole Body Vibration Immediately Decreases Lower Extremity Loading During the Drop Jump.

Chen, Z-R, Peng, H-T, Siao, S-W, Hou, Y-T, and Wang, L-I. Whole body vibration immediately decreases lower extremity loading during the drop jump. J Strength Cond Res 30(9): 2476-2481, 2016-The purpose of this study was to evaluate the acute effect of whole body vibration (WBV) on lower extremity loading during the drop jump (DJ). Fifteen male collegiate physical education students randomly completed 3 experimental sessions on 3 separate days with 4 days interval between sessions (performing 3 trials of DJ from 30-, 40-, and 50-cm drop heights before WBV and 4 minutes after WBV). Eight cameras and 2 force platforms were used to record kinematic and kinetic data, respectively. Peak impact force and loading rate significantly decreased after WBV during DJ from 40 and 50 cm. Knee angular displacements significantly increased after WBV during DJ from 30, 40, and 50 cm. Whole body vibration may help immediately reduce lower extremity loading.

The acute effect of drop jump protocols with different volumes and recovery time on countermovement jump performance.

The aim of this study was to investigate the acute effect of (a) a drop jump (DJ) protocol with 1 set per 5 repetitions and (b) a DJ protocol with 2 sets per 5 repetitions on countermovement jump (CMJ) height performance in volleyball players at recovery times of (a) 2 minutes, (b) 6 minutes, and (c) 12 minutes. The subjects were 10 male Division I college volleyball players. They were instructed to perform a pretest of 3 CMJs and then randomly assigned to perform (a) a DJ protocol with 1 set per 5 repetitions and (b) a DJ protocol with 2 sets per 5 repetitions. After the DJ, 3 CMJs were completed in 2, 6, and 12 minutes. A 2-way repeated-measures analysis of variance was used to examine the differences between training volumes and recovery times in CMJ height (H(CMJ)) and maximum ground reaction force. Both DJ training volumes significantly increased the H(CMJ). The H(CMJ) at post 2 minutes was greater than those at the pretest (p = 0.008), post 6 minutes (p = 0.004), and post 12 minutes (p = 0.002). In addition, the H(CMJ) at post 6 minutes was significantly greater than that at post 12 minutes (p = 0.018). Drop jumps in lower volume (e.g., within 10 repetitions) and short recovery time (e.g., within 2 minutes) can produce a positive acute effect on CMJ performance.