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Karate athletes strategically use lower-limb techniques in combat, with the roundhouse kick (mawashi geri) being highly effective in kumite. To quickly improve the technical performance before training or competitions, conditioning activities (CAs) are often utilized. Recently, Whole-Body Vibration (WBV) has emerged as a potential conditioning activity (CA). This study aimed to analyze the acute effects of WBV as a CA on the performance of the mawashi geri. The sample included sixteen male karate athletes. The study had a familiarization and two experimental sessions: one with WBV and the other without (NWBV), conducted randomly and counterbalanced, each preceded and followed by a mawashi geri assessment on a force platform. During the CA intervention, the participants performed four sets of isometric half-squats on a vibration platform at a frequency of 26 Hz and an amplitude of 4 mm in the WBV condition, while the platform was off in the NWBV condition. A significant reduction in the mawashi geri attack phase time was observed under the WBV condition [pre: 0.31 ± 0.03 s; post: 0.30 ± 0.03 s] compared to the NWBV condition [pre: 0.31 ± 0.04 s; post: 0.32 ± 0.03 s] (p = 0.02). However, no differences were noted regarding the impact force or other kinetic variables between the conditions. Therefore, WBV did not increase the performance of the kinetic and kinematic variables of the mawashi geri in karate athletes, but it is possible that there is a positive effect on attack time, suggesting that further studies with different vibration protocol configurations would be beneficial. [ABSTRACT FROM AUTHOR]

Featured Application: The proposed moving camera method allows for 2D kinematical swimming analysis with no field of view limitation and with better accuracy and precision than those using a single static camera. Despite its limitations, 2D kinematical analysis remains a simple and valid alternative for swimming analysis. This analysis is limited by the length of the field of view, and the reconstruction errors are proportional to the calibrated area. A possible solution for these problems is the usage of moving cameras that allow for tracking an object across a larger area without the concerns of the calibration area. The purpose of this study was to verify the viability of the utilization of moving cameras for underwater 2D kinematical analysis. Two calibration processes were evaluated: (i) obtaining the extrinsic parameters for every frame based on pool markers (M1) and; (ii) constraining the degrees of freedom of the camera's movements and tracking translation based on the principal point (M2). M1 obtained better accuracy in reconstructing the coordinates of static markers (mean error: 12.1 against 14.2 mm from a static camera) and in the estimation of the rod length (−2.6 vs. 12.6 mm). M2 obtained better accuracy when evaluating the distance between the points (−0.3 mm) than that for position estimation (58.6 mm). The results indicate that moving cameras are a viable alternative for 2D underwater kinematic analysis, but M2 had limitations about real position extraction. [ABSTRACT FROM AUTHOR]

Purpose. The present study aimed to describe the main characteristics of Brazilian surfers and their injuries, and to analyze the probability of developing injuries according to skill level, experience in surfing, training volume, and age. Methods. A total of 1829 Brazilian surfers answered an electronic survey about their characteristics and previous and current injuries. The association between participant characteristics and percentage of injuries was investigated using a chi-squared test. The statistical significance of the results was assumed at a p-value < 0.05. The prevalence ratio (PR) was also calculated to illustrate the probability of having injuries. Results. Most surfers are men (84.2%), young adults (72.0%), with more than 2 years of experience in surfing (60.7%), with an intermediate level of skill (49.3%), recreational surfers (99.2%), and who practice surfing 1 to 2 days a week (79.7%) for 1 to 3 hours a day (65.9%). About 55.5% of the participants were already affected by an injury or had some surfing-related pain. In the last 12 months, 52.2% of surfers suffered injuries. For both, more than 50% of injuries occurred in the lower limbs. Brazilian surfers with higher skill levels, time of experience, hours per day of surf training, and age presented higher prevalence ratios of previous and current injuries. Conclusions. In summary, Brazilian surfers are predominantly male, young adults, and non-competitive athletes. The most injured anatomical region in this group is the lower limbs. Contrary to expectation, higher experience and skill levels might not act as protective factors against injuries due to increased training volume. [ABSTRACT FROM AUTHOR]

Aim: The authors investigated how the Arena Powerskin R-EVO Closed Back swimsuit and Arena Carbon Triwetsuit (full-sleeve wetsuit), both approved by the Fédération Internationale de Natation (FINA) regulations, affect biomechanics and energetics of 3 elite female open water (OW) swimmers at maximal and 4 submaximal swimming intensities. Methods: Three elite female OW swimmers (OW1 = 24 y, 1.64 m, 60 kg; OW2 = 23 y, 1.69 m, 65 kg; OW3 = 27 y, 1.63 m, 64.5 kg) were tested 1 week prior to a FINA/CNSG (China National Sports Group) Marathon Swim World Series event and 40 days before the 18th FINA World Championships 2019. Each OW swimmer completed 2 identical testing sessions, one with a swimsuit and other with a wetsuit, involving shoulder flexion power output assessed from medicine-ball throw, maximal performance and drag coefficient assessment, and an incremental intermittent swim test at 4 different relative intensities. Results: Estimated peak oxygen uptake was 4.4 L·min−1 for OW1, 5.6 L·min−1 for OW2, and 5.0 L·min−1 for OW3. Despite a distinct behavior observed on index of coordination for OW3, a null index of synchronization, increased stroke rate (mean difference = 2%–8%), reduced drag factor (minimum = −14%; maximum = −30%), lower energy cost (mean difference = −2% to −6%), and faster performance (mean difference = 2% to 3%) were observed with the wetsuit compared with swimsuit for all elite OW swimmers. Conclusion: The wetsuit enhances submaximal swimming performance, and this increase is dependent on the OW swimmer's characteristics. The higher stroke rate and lower stroke length detected with wetsuit could be related to movement constraints imposed by the suit. [ABSTRACT FROM AUTHOR]

Introduction: People with chronic low back pain have functional disability associated with a decrease in productivity with major socioeconomic consequences. Resistance training is a form of exercise treatment that has been proposed to mitigate the problems caused by low back pain. It is recommended that the resistance training exercises focus on the posterior chain muscles and that the fragile condition of this population be considered. To the best of our knowledge, no study has yet investigated the effects of an acute resistance training session on pain and functional disability, considering such recommendations for people with non-specific chronic low back pain. Objective: Our aim was to assess the effects of a single resistance training session on pain and functional disability in people with non-specific chronic low back pain. Methods: 31 subjects of both genders with non-specific chronic low back pain took part in the study. Participants were randomized into two groups: the resistance training group (RTG) and the control group (CG). The RTG underwent a single exercise session. Results: The RTG showed a significant (p=0.001) decrease in perceived pain (5.9±1.6 versus 4.9±1.8) and a significant (p=0.016) decrease in functional disability (25.6±6.3 versus 20.5±4.1), after the resistance training session. The CG did not show significant differences (p=0.190) in perceived pain (6.9±1.7 versus 7.4±1.9)and in functional disability (26.8±7.8 versus 27.8 ±9.2), after the final assessment. The RTG showed a significant (p=0.001) increase in strength between the initial and final assessments (47.7 ±26.6kgf versus 60.2 ±31.4kgf) while the CG did not show any differences. Conclusion: A single resistance training session reduces pain and functional disability in people with chronic non-specific low back pain. [ABSTRACT FROM AUTHOR]

Intra- and inter-cycle velocity variations are of utmost importance for achieving enhanced swimming performances. However, intra-cycle events can impact and interfere with the subsequent cycles, making relevant to study several consecutive cycles allowing a better understanding of this possibility. We have assessed front crawl intra- and inter-cyclic velocity variations and overall biomechanical variables in sprint front crawl swimming. Twenty-seven elite swimmers performed 25 m all-out front crawl, were videotaped using moving cameras placed at the sagittal plane and were grouped according to their sprint mean velocity. Coefficient of variation, root mean square error and mean velocity differences between two consecutive paired cycles allowed assessing intra- and inter-cycle velocity variations. Visual inspection was performed to analyse possible variability causes and independent-measures t-test allowed comparing groups. Sprint front crawl was characterised by intra- (11.12 ± 2.98) and inter-cycle velocity variation (2.27 ± 0.80 of inter-cycle velocity coefficient of variation and 0.031 ± 0.014 of root mean square error), with no differences between fastest and slowest swimmers. Front crawl intra-cycle velocity variation was not related to mean velocity and cycle sequence but considered swimmers’ personal strategy. Despite some abnormal oscillations within cycles, inter-cycle velocity variation was not caused by intra-cycle velocity variation, mean velocity or cycle sequence. [ABSTRACT FROM AUTHOR]

The popularization of whole-body mechanical vibration training has made necessary to consider safety aspects of whole-body vibration training. In order to understand how vibration affects the human body, two important indices are calculated from acceleration data: transmissibility and estimated Vibration Dose Value (eVDV). This study aims to compare the acceleration and transmissibility to the head (TH) between different frequencies of WBV in the isometric semi-squat exercise as well as to classify the acceleration and eVDV from normative values established in literature. Twenty-four individuals (25.65 ± 5.22 years; 84.44 ± 21.91 kg; 1.73.80 ± 0.21 m; 14.28 ± 6.27% fat) who exercise regularly participated in the study. There were four, 30-second repetitions of semi-squatting in the frequencies of 5 Hz, 15 Hz, and 22 Hz, with a 30-second rest between the repetitions. One frequency per day was applied over the course of three days. The acceleration was previously measured at the base of the platform at each frequency and then measured in the head. A one-way ANOVA parametric test with repeated measures was performed to compare the acceleration and transmissibility to the head between frequencies, considering a significance equal to p<0.05. The 5 Hz frequency presented lower values of acceleration and higher transmissibility to the head in relation to the other frequencies. The training protocol adopted in this study can be considered safe regarding transmissibility to the head. On the other hand, considering the ISO-2631 normative values, the protocol can be considered uncomfortable regarding estimated Vibration Dose Value. As to the frequencies used, 5 Hz is more applicable considering acceleration and estimated Vibration Dose Value; however, it presents higher transmissibility to the head. [ABSTRACT FROM AUTHOR]

It has been postulated that the mechanical and neurophysiological effects induced by stretching decrease maximal muscle strength and power. Additionally, the reduction in neural input and muscle stiffness can affect the joint stabilization process. However, there is no evidence available to support this hypothesis. Thus, the aim of this study is to analyze the influence of static stretching on dynamic joint stability. Twenty physically active female university students (22.8 ± 5.3 years; 58 ± 8.8 kg; 1.62 ± 0.07 m) performed a series of static-passive stretching exercises for the peroneus longus and brevis muscles (four repetitions of 30 s). Before and after the stretches, electromyography was performed on both muscles during simulated ankle sprain. Mathematical algorithms calculate the latency and the electromyography activity (RMS). After stretching, the latency increased from 66ms to 73 ms (p = 0.003) for the peroneus brevis muscle and from 70 ms to 79 ms (p = 0.001) for the peroneus longus muscle. The RMS, calculated 100 ms after the simulation, decreased in the peroneus brevis muscle, from 25.05 to 18.16 (p = 0.001), and in the peroneus longus muscle, from 22.84 to 15.61 (p = 0.001). Muscle stretching changed the motor responses of both muscles. The increase in latency and the decrease in RMS indicate that static stretching influences the neuromuscular function involved in the joint stabilization process. [ABSTRACT FROM AUTHOR]

Background: Knee pain during stair managing is a common complaint among individuals with PFP and can negatively affect their activities of daily living. Gait modification programs can be used to decrease patellofemoral pain. Immediate effects of a stair descent distal gait modification session that intended to emphasize forefoot landing during stair descent are described in this study. Objectives: To analyze the immediate effects of a distal gait modification session on lower extremity movements and intensity of pain in women with patellofemoral pain during stair descent. Method: Nonrandomized controlled trial. Sixteen women with patellofemoral pain were allocated into two groups: (1) Gait Modification Group (n = 8); and 2) Control Group (n = 8). The intensity of pain (visual analog scale) and kinematics of knee, ankle, and forefoot (multi-segmental foot model) during stair descent were assessed before and after the intervention. Results: After the gait modification session, there was an increase of forefoot eversion and ankle plantarflexion as well as a decrease of knee flexion. An immediate decrease in patellofemoral pain intensity during stair descent was also observed. Conclusion: The distal gait modification session changed the lower extremity kinetic chain strategy of movement, increasing foot and ankle movement contribution and decreasing knee contribution to the task. An immediate decrease in patellofemoral pain intensity during stair descent was also observed. To emphasize forefoot landing may be a useful intervention to immediately relieve pain in patients with patellofemoral pain during stair descent. Clinical studies are needed to verify the gait modification session effects in medium and long terms. [ABSTRACT FROM AUTHOR]

The purpose of this study was to verify the acute effect of different vibration frequencies on countermovement jump (CMJ) performance after Whole Body Vibration (WBV) training. The sample consisted of 24 men who attended the laboratory to perform a WBV protocol, each day with a different vibration frequency (5, 15, 22, or 30 Hz). The sessions consisted of a warm-up, 3 CMJ attempts, followed by WBV training that consisted of 4 x 30 sec with a 30-sec interval between sets. The CMJ was again performed (3 attempts 1 min and 3 attempts 5 min post WBV). Analyzing the performance delta values for Δ5CMJ (height 5 min after WBV - height pre WBV), the frequency of 22 Hz presented higher delta than 30 Hz (1.11 ± 2.61 vs. -0.71 ± 2.61 cm; P=0.03). When comparing the highest performance with baseline, regardless of the vibration frequency, there was a difference for both 1 min (36.8 ± 4.69 vs. 34.92 ± 5.04 cm; P=0.01) as for 5 min (36.84 ± 5.19 vs. 34.92 ± 5.04 cm; P=0.01). Despite the better performance at 22 Hz compared to 30 Hz, analysis between the highest and baseline performance suggests that each individual may have a specific frequency to which the neuromuscular system is more responsive. [ABSTRACT FROM AUTHOR]

The aim of this study was to verify if the mechanical vibration in the exercise of isometric push-up affects the electrical activity of muscles of the upper limbs and the time until the exhaustion. The subjects were 13 experienced strength-training volunteers (25.52 ± 4.44 yrs). The push-up exercise with vibration of 20 Hz (V20) was accomplished until the exhaustion in one day and on another day without vibration (V00). The electromyographic activity (EMG) of the triceps brachii (TRB) and pectoralis (PT) was measured. There was no difference in the exercise duration between V20 and V00 (P = 0.954), but in the analysis of the complete signal, the Root Mean Square (RMS) of the TRB and PT was higher in V20 compared to V00 (P = 0.015, P = 0.018, respectively) and the Median Frequency (FMA) of the EMG was not different between the situations. The partial analysis of the EMG signal showed that in both muscles RMS was bigger in the 10 last sec (10f) and the FMA significantly lower in 10f compared to initial 10 sec. The findings indicate that the frequency vibration of 20 Hz increased the electrical activity of the upper limb muscles, but did not change the performance of strength resistance. [ABSTRACT FROM AUTHOR]