Static Balance in Hereditary Spastic Paraplegias: a Cross-sectional Study.

Motor and somatosensory pathway dysfunction due to degeneration of long tracts in hereditary spastic paraplegias (HSP) indicates that postural abnormalities may be a relevant disease feature. However, balance assessments have been underutilized to study these conditions. How does the static balance of individuals with HSP with eyes open and closed differ from healthy controls, and how does it relate to disease severity? This cross-sectional case-control study assessed the static balance of 17 subjects with genetically confirmed HSP and 17 healthy individuals, evaluating the center of pressure (COP) variables captured by a force platform. The root-mean-square of velocities and mean of displacements amplitudes in mediolateral and anteroposterior axes were correlated with disease severity. All COP parameters' performances were significantly impaired in HSP subjects compared to controls (p < 0.001 for all comparisons). COP with eyes open and closed differed for all variables within the HSP group, whereas in the control group, differences were observed only for anteroposterior velocity and amplitude. Spastic Paraplegia Rating Scale presented moderate direct correlations with the most COP variables (Rho = - 0.520 to - 0.736). HSP individuals presented significant postural instability with eyes open and to a greater extent with eyes closed, corroborating the clinical findings of somatosensorial and proprioceptive pathways dysfunction. The degrees of proprioceptive and motor impairments are mutually correlated, suggesting that similar pathophysiological mechanisms operate for the degeneration of these long tracts. COP parameters can be seen as disease severity biomarkers of HSP, and they should be assessed in future clinical trials.

Postural adjustments and perceptual responses of Nordic running: concurrent effects of poles and irregular terrain.

PURPOSE: In the natural environment, humans must continuously negotiate irregular and unpredictable terrain. Recently, the poles have been extensively used during trial running events. However, we know little about how humans adjust posture and bilateral coordination to use poles in irregular terrain. Here, we compared kinematics, bilateral coordination and perceptual responses between regular (compact dust) and irregular terrain (medium-length grass) during running at preferred speed with and without poles. METHODS: In this transversal observational study, thirteen young healthy adults (8 men; mean ± SD; age 29.1 ± 8.0 years, body mass 76.8 ± 11.4 kg; height 1.75 ± 0.08 m) were evaluated during running at a self-selected comfortable speed with and without poles on regular and irregular terrains. RESULTS: Our results show that, despite more flexed pattern on lower-limb joints at irregular terrain, the usage of poles was not enough to re-stabilize the bilateral coordination. Also, the perceived exertion was impaired adding poles to running, probably due to more complex movement pattern using poles in comparison to free running, and the invariance in the bilateral coordination. CONCLUSION: Besides the invariability of usage poles on bilateral coordination and lower-limb kinematics, the runners seem to prioritize postural stability over lower limb stiffness when running in medium-length grass given the larger range of ankle and knee motion observed in irregular terrain. Further investigations at rougher/hilly terrains will likely provide additional insights into the neuromotor control strategies used to maintain the stability and on perceptual responses using poles during running.

Pendular mechanism determinants and elastic energy usage during walking of obese and non-obese children.

The mechanical and metabolic responses of walking by obese children are not yet well understood. The objectives of this study were (1) to compare the pendular mechanism (recovery, phase shift by α and ß values, and ratio between forward and vertical mechanical work), the maximum possible elastic energy usage and the bilateral coordination during walking between non-obese and obese children, and (2) to verify if the bilateral coordination could contribute to understanding the pendular mechanism and elastic energy usage in these populations. Nine obese (six female, 8.7 ± 0.5 years, 1.38 ± 0.04 m, 44.4 ± 6.3 kg and 24.1 ± 3.50 kg/m2 ) and eight non-obese (four female, 7.4 ± 0.5 years, 1.31 ± 0.08 m, 26.6 ± 2.1 kg and 16.4 ± 1.40 kg/m2 ) children were analysed during walking on a treadmill at five speeds: 1, 2, 3, 4 and 5 km/h. The results indicated that although the mechanical energy response of the centre of mass during walking is similar between obese and non-obese children, the obese children showed a lower pendulum-like mechanism and greater elastic energy usage during level walking. Therefore, obese children seem to use more elastic energy during walking compared to non-obese children, which may be related to their apparent higher positive work production during the double support phase. Finally, bilateral coordination presented high values at slow speeds in both groups and requires further attention due to its association with falls. NEW FINDINGS: What is the central question of this study? Are there any differences of the pendular and elastic mechanisms and bilateral coordination during walking between non-obese and obese children? What is the main finding and its importance? To our knowledge, this study is the first to analyse the mechanical energy usage and the bilateral coordination of obese and non-obese children during walking. Obese children had a lower pendular recovery mechanism and used more elastic energy compared to non-obese children. The bilateral coordination was higher at slow speeds in both groups and requires further attention due to its association with falls.

Energetic responses of head-out water immersion at different temperatures during post-exercise recovery and its consequence on anaerobic mechanical power.

PURPOSE: While exercise recovery may be beneficial from a physiological point of view, it may be detrimental to subsequent anaerobic performance. To investigate the energetic responses of water immersion at different temperatures during post-exercise recovery and its consequences on subsequent anaerobic performance, a randomized and controlled crossover experimental design was performed with 21 trained cyclists. METHOD: Participants were assigned to receive three passive recovery strategies during 10 min after a Wingate Anaerobic Test (WAnT): control (CON: non-immersed condition), cold water immersion (CWI: 20 â„ƒ), and hot water immersion (HWI: 40 â„ƒ). Blood lactate, cardiorespiratory, and mechanical outcomes were measured during the WAnT and its recovery. Time constant (τ), asymptotic value, and area under the curve (AUC) were quantified for each physiologic parameter during recovery. After that, a second WAnT test and 10-min recovery were realized in the same session. RESULTS: Regardless the water immersion temperature, water immersion increased [Formula: see text] (+ 18%), asymptote ([Formula: see text]+ 16%, [Formula: see text] + 13%, [Formula: see text] + 17%, HR + 16%) and AUC ([Formula: see text]+ 27%, [Formula: see text] + 18%, [Formula: see text] + 20%, HR + 25%), while decreased [Formula: see text] (- 33%). There was no influence of water immersion on blood lactate parameters. HWI improved the mean power output during the second WAnT (2.2%), while the CWI decreased 2.4% (P < 0.01). CONCLUSION: Independent of temperature, water immersion enhanced aerobic energy recovery without modifying blood lactate recovery. However, subsequent anaerobic performance was increased only during HWI and decreased during CWI. Despite higher than in other studies, 20 °C effectively triggered physiological and performance responses. Water immersion-induced physiological changes did not predict subsequent anaerobic performance.

Determinants of Dual-task Gait Speed in Older Adults with and without Parkinson's Disease.

Mobility difficulties for people with Parkinson's disease (PwPD) are more pronounced when they perform a simultaneous cognitive task while walking. Although it is known that neurodegeneration results in widespread motor and brain impairments, few studies have comprehensively examined possible physical and mental determinants of dual task walking in PwPD. In this cross-sectional study, we aimed to investigate if and how muscle strength (sit-to-stand 30-sec test), cognition (mini-mental state examination) and functionality (timed up and go test) affect walking performance (10-meter walking test) with and without arithmetic dual task from older adults with and without Parkinson's disease. Walking speed was reduced by 16% and 11% with arithmetic dual task for PwPD (from 1.07±0.28 to 0.91±0.29 m.s-1, p<0.001) and older adults (from 1.32±0.28 to 1.16±0.26 m.s-1, p=0.002) compared to essential walking. The cognitive state was similar among the groups, but it was only associated with the dual-task walking speed in PwPD. In PwPD, lower limb strength was the better predictor of speed, whereas mobility was more related to it in older adults. Therefore, future exercise interventions aiming to improve walking in PwPD should consider these findings to maximize their effectiveness.

Quantifying physiological and biomechanical responses of shallow water walking: a systematic review and meta-analysis.

Detecting the physiological and biomechanical alterations in shallow water walking (SWW) due to water depth and speed is important for health professionals to perform accurate exercise prescription. This systematic review with meta-analysis aimed to investigate the acute physiological and biomechanical responses of SWW at different immersion depths in comparison to dry land walking. The main result (initial search: 1960 studies; systematic review: 42 studies; meta-analysis: 22 studies) indicated that metabolic power was higher in the immersion depth levels of xiphoid process (standardized mean differences (SMD) = 0.90; 95% confidence intervals (CI): 0.26 to 1.54) and waist (SMD = 3.35; 95% CI: -0.18 to 6.87) in comparison to dry land. SWW at xiphoid and waist depths seems to be an adequate exercise if the objective is to increase the energy expenditure and cardiovascular demand while the lower limb impact forces are reduced in comparison to dry land walking. PROSPERO registration: CRD42018113040.

Progression of Functional Gait in Hereditary Spastic Paraplegias.

Hereditary spastic paraplegias (HSP) are characterized by progressive deterioration of axonal projections of upper motor neurons leading to abnormal locomotion. The clinical course of HSP as well as the definition of the best instruments to assess its progression is largely unknown. The aim of this study was to investigate the progression of functional gait in individuals with HSP and to define sensitivity to change, minimal clinically important difference (MCID), and validity of timed functional tests of gait (TFT). The study was constituted of two phases: a cross-sectional study and a prospective cohort of 18 months. Twenty-five patients (17 being SPG4), and twenty-five age- and sex-matched control individuals performed TFT. Spastic paraplegia rating scale (SPRS), ten-meter walking test (10MWT), timed up and go test (TUG), both at self-selected and maximal walking speeds, and six-minute walking test (6MWT) were performed on baseline in both groups and after 18 months of follow-up only in the HSP cohort. In the cross-sectional analysis, all TFTs performances were greatly impaired in HSP patients compared to controls. After 18 months of follow-up, TFTs did not differ significantly from baseline in the statistical analysis, with some tests showing more frequent improvement than worsening. We have provided effect size measures and MCID for the evaluated instruments. HSPs clearly compromised TFTs performances, which were valid instruments for assessing disease severity. However, TFTs and SPRS did not capture the very slow motor evolution of HSPs, reinforcing the necessity of additional biomarkers of disease progression.

Biomechanical responses of Nordic walking in people with Parkinson's disease.

In healthy adults, Nordic walking (NW) is known to increase the external mechanical energy fluctuations, though the external work is unaltered due to an improved pendulum-like recovery in comparison with free walking (FW). We aimed to compare mechanical, pendulum-like, and spatiotemporal parameters of gait at different speeds with and without NW poles in people with Parkinson's disease and healthy controls. The study included 11 people (aged 65.6 ± 7.0 years) with idiopathic Parkinson's disease, scoring between 1 and 1.5 on the Hoehn and Yahr scale (H&Y), and nine healthy controls (aged 70.0 ± 5.6 years). All the people were experienced Nordic walkers. Walking tests were performed at 1.8 km h-1 and 4.7 km h-1 , on eight 3D force platforms on a walkway. We found greater pendulum-like energy recovery (p < 0.05) in the Parkinson group during NW than in FW, while external mechanical work remained similar (p > 0.05). People with Parkinson's disease showed a major increase in vertical and forward energy fluctuations using poles than in healthy controls. In addition, the Parkinson group showed increased stride frequency and reduced stride length compared to controls in the NW and FW conditions. Our findings partly justify the lower walking economy in Parkinson's disease due to reduced pendulum-like mechanism at commonly used speeds. NW alters gait mechanics similarly in Parkinson group and healthy control, increasing the total mechanical work. Therefore, NW can be a compelling strategy for rehabilitation because of its potential for improving functional mobility, increasing pendulum-like mechanism in Parkinson's disease.

Transfer of strength training to running mechanics, energetics, and efficiency.

To examine the effects of increased strength on mechanical work, the metabolic cost of transport (Cost), and mechanical efficiency (ME) during running. Fourteen physically active men (22.0 ± 2.0 years, 79.3 ± 11.1 kg) were randomized to a strength-training group (SG, n = 7), who participated in a maximal strength training protocol lasting 8 weeks, and a control group (CG, n = 7), which did not perform any training intervention. Metabolic and kinematic data were collected simultaneously while running at a constant speed (2.78 m·s-1). The ME was defined as the ratio between mechanical power (Pmec) and metabolic power (Pmet). The repeated measures two-way ANOVA did not show any significant interaction between groups, despite some large effect sizes (d): internal work (Wint, p = 0.265, d = -1.37), external work (Wext, p = 0.888, d = 0.21), total work (Wtot, p = 0.931, d = -0.17), Pmec (p = 0.917, d = -0.17), step length (SL, p = 0.941, d = 0.24), step frequency (SF, p = 0.814, d = -0.18), contact time (CT, p = 0.120, d = -0.79), aerial time (AT, p = 0.266, d = 1.12), Pmet (p = 0.088, d = 0.85), and ME (p = 0.329, d = 0.54). The exception was a significant decrease in Cost (p = 0.047, d = 0.84) in SG. The paired t-test and Wilcoxon test only detected intragroup differences (pre- vs. post-training) for SG, showing a higher CT (p = 0.041), and a lower Cost (p = 0.003) and Pmet (p = 0.004). The results indicate that improved neuromuscular factors related to strength training may be responsible for the higher metabolic economy of running after 8 weeks of intervention. However, this process was unable to alter running mechanics in order to indicate a significant improvement in ME.

Mechanical work as a (key) determinant of energy cost in human locomotion: recent findings and future directions.

NEW FINDINGS: What is the topic of this review? This narrative review explores past and recent findings on the mechanical determinants of energy cost during human locomotion, obtained by using a mechanical approach based on König's theorem (Fenn's approach). What advances does it highlight? Developments in analytical methods and their applications allow a better understanding of the mechanical-bioenergetic interaction. Recent advances include the determination of 'frictional' internal work; the association between tendon work and apparent efficiency; a better understanding of the role of energy recovery and internal work in pathological gait (amputees, stroke and obesity); and a comprehensive analysis of human locomotion in (simulated) low gravity conditions. ABSTRACT: During locomotion, muscles use metabolic energy to produce mechanical work (in a more or less efficient way), and energetics and mechanics can be considered as two sides of the same coin, the latter being investigated to understand the former. A mechanical approach based on König's theorem (Fenn's approach) has proved to be a useful tool to elucidate the determinants of the energy cost of locomotion (e.g., the pendulum-like model of walking and the bouncing model of running) and has resulted in many advances in this field. During the past 60 years, this approach has been refined and applied to explore the determinants of energy cost and efficiency in a variety of conditions (e.g., low gravity, unsteady speed). This narrative review aims to summarize current knowledge of the role that mechanical work has played in our understanding of energy cost to date, and to underline how recent developments in analytical methods and their applications in specific locomotion modalities (on a gradient, at low gravity and in unsteady conditions) and in pathological gaits (asymmetric gait pathologies, obese subjects and in the elderly) could continue to push this understanding further. The recent in vivo quantification of new aspects that should be included in the assessment of mechanical work (e.g., frictional internal work and elastic contribution) deserves future research that would improve our knowledge of the mechanical-bioenergetic interaction during human locomotion, as well as in sport science and space exploration.

Effect of photobiomodulation therapy on performance and running economy in runners: A randomized double-blinded placebo-controlled trial.

The objective of this study was to evaluate effects of photobiomodulation therapy (PBMT) on the 3000 m running performance (primary outcome), running economy (RE), metabolic cost and ratings of perceived exertion during running (secondary outcomes). Twenty male endurance athletes performed 4-min treadmill rectangular test at 12 km.h-1 monitored by a gas analyser. After that, PBMT or placebo in each lower limb was applied, followed performed a maximum test of 3000 m. Immediately after 3000 m test, the athletes repeated the treadmill test. Another application of PBMT/placebo was done after the treadmill test, and athletes went back to the laboratory 24 h later to repeat the treadmill test. After a 72 h interval, athletes repeated all procedures with another treatment intervention (PBMT/placebo). Athletes performed the 3000 m running test ~7s faster when treated with PBMT with similar effort score compared placebo condition. The RE remains unchanged immediately post 3000 m running test, nonetheless RE measured post-24 h improved by 5% with PBMT application without changes in metabolic cost. The PBMT pre- and post-conditioning enhanced the 3000 m running performance and improved RE 24 h following the 3000 m test. However, no changes on ratings of perceived exertion and metabolic cost with the application of PBMT.

Correlations Between Jump Performance in Block and Attack and the Performance in Official Games, Squat Jumps, and Countermovement Jumps of Professional Volleyball Players.

ABSTRACT: Berriel, GP, Schons, P, Costa, RR, Oses, VHS, Fischer, G, Pantoja, PD, Kruel, LFM, and Peyré-Tartaruga, LA. Correlations between jump performance in block and attack and the performance in official games, squat jumps, and countermovement jumps of professional volleyball players. J Strength Cond Res 35(12S): S64-S69, 2021-The jump used in performance tests must be chosen according to the specificity. The aims of the present study were to analyze the correlations between height and reach of block and attack jumps and the effectiveness of such actions in official games and also the relationship between height and reach of attack and block jumps and the height achieved in squat jump (SJ), countermovement jump (CMJ), and CMJ with an arms swing (CMJA). Thirteen, male, professional volleyball players who competed in the Brazilian Volleyball Super League participated in this study. Evaluations of height and reach of attack and block jumps and height of SJ, CMJ, and CMJA were performed. Attack and block effectiveness were evaluated in 8 official games. Pearson's product-moment correlation coefficient was used, and the significance level was set at α ≤ 0.05. Attack jump height correlated with attack effectiveness in the games (r = 0.57; p = 0.05). Block jump height presented a very large correlation with SJ height (r = 0.82; p < 0.01), and attack jump height presented a very large correlation with CMJ height (r = 0.86; p < 0.01). Success in attack actions is directly associated with the athlete's ability to perform a vertical jump. Moreover, SJ, CMJ, and CMJA tests provided information of great applicability for the volleyball players' needs. Because of the relevance of the results, these tests should be included in the assessment routine of professional volleyball players.

Kinematic Comparison of the Roundhouse Kick Between Taekwondo, Karate, and Muaythai.

ABSTRACT: Diniz, R, Del Vecchio, FB, Schaun, GZ, Oliveira, HB, Portella, EG, da Silva, ES, Formalioni, A, Campelo, PCC, Peyré-Tartaruga, LA, and Pinto, SS. Kinematic comparison of the roundhouse kick between taekwondo, karate, and muaythai. J Strength Cond Res 35(1): 198-204, 2021-The roundhouse kick (RHK) is frequently executed in taekwondo, karate, and muaythai because of its high technical effectiveness during combat. The purpose of this study was to compare kinematic characteristics during RHK performance between taekwondo, karate, and muaythai athletes. Forty-seven male athletes (25.5 ± 4.7 years, 1.75 ± 0.1 m, and 75.8 ± 11.5 kg) volunteered to participate (taekwondo: 17; karate: 15; and muaythai: 15). Self-selected distance from target, mean and peak fifth metatarsus linear velocity (LV5mean; LV5peak), mean and peak hip (HAVmean; HAVpeak) and knee (KAVmean; KAVpeak) angular velocities, as well as target linear acceleration (TLA) were analyzed with a 3D video motion analysis system. Comparisons between modalities were performed with 1-way analysis of variances and Bonferroni's post hoc test (α = 0.05). Self-selected distance was lower in muaythai compared with taekwondo and karate (p < 0.001). Also, karate had greater LV5mean compared with muaythai (p = 0.001), and muaythai showed higher HAVmean than karate (p = 0.011). In addition, HAVpeak was greater in muaythai than in taekwondo and karate (p < 0.001). No differences were found for KAVmean, KAVpeak, and TLA. Although it is similarly described between modalities, RHK showed distinct kinematic characteristics between taekwondo, karate, and muaythai. Based on these results, coaches and athletes can improve their RHK technique according to the specificities of each combat sport. Specifically, it is suggested that combat strategies should aim to increase the distance from the opponent during combat for muaythai athletes, whereas taekwondo and karate athletes should focus on decreasing it.

When mechanical work meets energetics: Obese versus non-obese children walking.

NEW FINDINGS: What is the central question of this study? The aim was to compare the cost of transport and mechanical work between obese and non-obese children at different walking speeds. What is the main finding and its importance? Our data show that the cost of transport, mechanical efficiency and work are similar and directly mass dependent in obese and non-obese children. The optimal walking speed (most economical walking speed) is reduced in obese children. ABSTRACT: Although studies have shown the influence of gait biomechanics on the metabolic economy in obese adults and adolescents, little is known regarding obese children. We compared the metabolic cost of transport, apparent mechanical efficiency and gait biomechanics (assessed by mechanical energy fluctuations) in obese children (n = 12; mean ± SD: 8.6 ± 0.51 years of age, 1.38 ± 0.04 m, 44.6 ± 6.65 kg, 24.1 ± 3.50 kg m-2 ) and age- and sex-matched non-obese children (n = 12, 7.8 ± 0.90 years of age, 1.31 ± 0.08 m, 26.8 ± 2.24 kg, 16.4 ± 1.40 kg m-2 ) while walking at different speeds (from 1 to 5 km h-1 ) on a treadmill. We found that the mechanical efficiency was higher at 3 km h-1 compared with the remaining speeds for both groups (P < 0.05). Although the internal mechanical work has been greater in obese compared with non-obese children at 4 and 5 km h-1 , the external, total mechanical work and the mechanical efficiency remained similar between obese and non-obese children at all speeds. Likewise, the cost of transport was similar in the two groups, although the optimal walking speed was an average of 0.4 km h-1 slower in obese children. Clearly, these results show that the walking economy is associated with the total mechanical work in obese and non-obese children. Finally, the reduced functional mobility in obese children observed in previous studies seems to be associated with a reduction in optimal walking speed in comparison to non-obese children.

Can Samba and Forró Brazilian rhythmic dance be more effective than walking in improving functional mobility and spatiotemporal gait parameters in patients with Parkinson's disease?

BACKGROUND: Parkinson's disease (PD) causes motor and nonmotor disorders in patients. Unlike aerobic training, potential adaptations from the practice of dance are less understood in PD, particularly compared with better known exercise modes. This study aimed to verify and compare the effects of a Brazilian dance program, inspired by Samba and Forrró rhythms, and a walking program on functional mobility and spatiotemporal gait parameters in patients with PD. METHODS: Eighteen participants with PD were divided into a dance group (DG) and a walking group (WG) and were assessed before and after an intervention period of 24 1-h sessions, performed twice per week for 12 weeks. The timed-up-and-go test (TUG) and walking kinematics at self-selected speed (SSS) and fast speed (FS) were determined. The generalized estimating equation method was used to compare the DG and WG pre- and post-intervention and to evaluate the group*time interaction (α <  0.05). RESULTS: Both groups demonstrated a significant improvement in TUG test at SSS (p = 0.02; effect size [ES] = 0.42) and FS (p = 0.02; ES = 0.24). In general, spatiotemporal parameters remained unchanged, except at SSS, in which the DG increased the stride frequency (p = 0.011; ES = 0.72). At FS, the swing time demonstrated a significant group*time interaction (p <  0.001; ES = 1.10), in which the two groups exhibited different behaviors: DG decreased (p = 0.015) and WG increased (p = 0.012). CONCLUSIONS: Functional mobility improved similarly in both groups. The results suggest that a 12-week program of Brazilian dance was sufficient to produce improvements in functional mobility and gait in individuals with PD. TRIAL REGISTRATION: This study is registered with the International Clinical Trial Registry under number NCT03370315 . Registered December 28, 2017 - Retrospectively registered.

Estimates of Running Ground Reaction Force Parameters from Motion Analysis.

We compared running mechanics parameters determined from ground reaction force (GRF) measurements with estimated forces obtained from double differentiation of kinematic (K) data from motion analysis in a broad spectrum of running speeds (1.94-5.56 m⋅s-1). Data were collected through a force-instrumented treadmill and compared at different sampling frequencies (900 and 300 Hz for GRF, 300 and 100 Hz for K). Vertical force peak, shape, and impulse were similar between K methods and GRF. Contact time, flight time, and vertical stiffness (kvert) obtained from K showed the same trend as GRF with differences < 5%, whereas leg stiffness (kleg) was not correctly computed by kinematics. The results revealed that the main vertical GRF parameters can be computed by the double differentiation of the body center of mass properly calculated by motion analysis. The present model provides an alternative accessible method for determining temporal and kinetic parameters of running without an instrumented treadmill.

Water-Based Concurrent Training Improves Peak Oxygen Uptake, Rate of Force Development, Jump Height, and Neuromuscular Economy in Young Women.

The study investigated the effects of different intrasession exercise sequences on the cardiorespiratory and neuromuscular adaptations induced by water-based concurrent training in young subjects. Twenty-six healthy young women (25.1 ± 2.9 years) were placed into 2 water-based concurrent training groups: resistance before (RA, n = 13) or after (AR, n = 13) aerobic training. Subjects trained resistance and aerobic training during 12 weeks, 2 times per week performing both exercise types in the same training session. Peak oxygen uptake (V[Combining Dot Above]O2peak), rate of force development (RFD) obtained during an isometric peak torque knee extension protocol, jump height, and neuromuscular economy (normalized electromyography at 80% of pretraining knee extension isometric peak torque) in young women were determined. After training, there was a significant increase (p < 0.001) in both RA and AR in the V[Combining Dot Above]O2peak, with no differences between groups (7 vs. 5%). The maximal isometric knee extension RFD showed significant increases (p = 0.003) after training (RA: 19 vs. AR: 30%), and both groups presented similar gains. In addition, the countermovement jump height also increased (p = 0.034) after training (RA: 5% vs. AR: 6%), with no difference between groups. After training, there were significant improvements on vastus lateralis (p < 0.001) (RA: -13% vs. AR: -20%) and rectus femoris (p = 0.025) (RA: -17% vs. AR: -7%) neuromuscular economy, with no difference between groups. In conclusion, 12 weeks of water-based concurrent training improved the peak oxygen uptake, RFD, jump height, and neuromuscular economy in young women independent from the intrasession exercise sequence.

Effects of Fatigue on Running Mechanics: Spring-Mass Behavior in Recreational Runners After 60 Seconds of Countermovement Jumps.

The purpose of this study was to investigate the effects of acute fatigue on spring-mass model (SMM) parameters among recreational runners at different speeds. Eleven participants (5 males and 6 females) performed running trials at slower, self-selected, and faster speeds on an indoor track before and after performing a fatigue protocol (60 s of countermovement jumps). Maximal vertical force (Fmax), impact peak force (Fpeak), loading rate (LR), contact time (Tc), aerial time (Ta), step frequency (SF), step length (SL), maximal vertical displacement of the center of mass (ΔZ), vertical stiffness (Kvert), and leg work (Wleg) were measured using a force plate integrated into the track. A significant reduction (-43.1 ± 8.6%; P < .05) in mechanical power during jumps indicated that the subjects became fatigued. The results showed that under fatigue conditions, the runners adjusted their running mechanics at slower (≈2.7 ms-1; ΔZ -12% and SF +3.9%; P < .05), self-selected (≈3.3 ms-1; SF +3%, SL -6.8%, Ta -16%, and Fmax -3.3%; P < .05), and faster (≈3.6 ms-1 SL -6.9%, Ta -14% and Fpeak -9.8%; P < .05) speeds without significantly altering Kvert (P > .05). During constant running, the previous 60 s of maximal vertical jumps induced mechanical adjustments in the spatiotemporal parameters without altering Kvert.

Effects of Fatigue on Running Mechanics: Spring-Mass Behavior in Recreational Runners After 60 Seconds of Countermovement Jumps.

The purpose of this study was to investigate the effects of acute fatigue on spring-mass model (SMM) parameters among recreational runners at different speeds. Eleven participants (5 males and 6 females) performed running trials at slower, self-selected, and faster speeds on an indoor track before and after performing a fatigue protocol (60 s of countermovement jumps). Maximal vertical force (Fmax), impact peak force (Fpeak), loading rate (LR), contact time (Tc), aerial time (Ta), step frequency (SF), step length (SL), maximal vertical displacement of the center of mass (Z), vertical stiffness (Kvert), and leg work (Wleg) were measured using a force plate integrated into the track. A significant reduction (-43.1 ± 8.6%; P < .05) in mechanical power during jumps indicated that the subjects became fatigued. The results showed that under fatigue conditions, the runners adjusted their running mechanics at slower (2.7 ms-1; Z -12% and SF +3.9%; P < .05), self-selected (3.3 ms-1; SF +3%, SL -6.8%, Ta -16%, and Fmax -3.3%; P < .05), and faster (3.6 ms-1 SL -6.9%, Ta -14% and Fpeak -9.8%; P < .05) speeds without significantly altering Kvert (P > .05). During constant running, the previous 60 s of maximal vertical jumps induced mechanical adjustments in the spatiotemporal parameters without altering Kvert.

Using heart rate to prescribe physical exercise during head-out water immersion.

The purpose of this study was to compare and correlate the effect of age group, sex, depth of water immersion, and the heart rate (HR) assessed out of the water on the HR behavior in individuals subjected to head-out water immersion. A total of 395 healthy individuals of both sexes, aged between 07 and 75 years, underwent vertical head-out water immersion. Heart rate was assessed out of the water in the supine and orthostatic (OHR) positions and at immersion depths corresponding to the ankle, knee, hip, umbilicus, xiphoid process, acromion, neck, and also the neck with the arms out of the water. The formula (ΔHR = OHR - HR immersion depth) was used to calculate the reduction in HR at each immersion depth. No age-based or sex-based differences in HR were found. The greater the depth of the water, the greater was the decrease in HR (p < 0.05); however, no differences were found between the HR values obtained below the depth corresponding to the umbilicus. Similarly, there was a significant relationship between OHR and ΔHR measured at levels below the depth corresponding to the umbilicus (e.g., xiphoid process level: r = 0.62; p < 0.05). Therefore, this study suggests to appropriately prescribe the intensity of water-based exercise intensity performed during vertical immersion: OHR should be measured before the individual entering the aquatic environment; ΔHR should be measured according to the depth at which exercise is to be performed, and we suggest an adaptation to Karvonen's HRmax prediction formula (predicted HRmax: 220 - age - ΔHR) to prescribe and control the intensity of the exercise performed during vertical immersion.