Determinants of age-related decline in walking speed in older women.

Background: Walking speed is reduced with aging. However, it is not certain whether the reduced walking speed is associated with physical and coordination fitness. This study explores the physical and coordination determinants of the walking speed decline in older women. Methods: One-hundred-eighty-seven active older women (72.2 ± 6.8 years) were asked to perform a 10-m walk test (self-selected and maximal walking speed) and a battery of the Senior fitness test: lower body strength, lower body flexibility, agility/dynamic balance, and aerobic endurance. Two parameters characterized the walking performance: closeness to the modeled speed minimizing the energetic cost per unit distance (locomotor rehabilitation index, LRI), and the ratio of step length to step cadence (walk ratio, WR). For dependent variables (self-selected and maximal walking speeds), a recursive partitioning algorithm (classification and regression tree) was adopted, highlighting interactions across all the independent variables. Results: Participants were aged from 60 to 88 years, and their self-selected and maximal speeds declined by 22% and 26% (p < 0.05), respectively. Similarly, all physical fitness variables worsened with aging (muscle strength: 33%; flexibility: 0 to -8 cm; balance: 22%; aerobic endurance: 12%; all p < 0.050). The predictors of maximal walking speed were only WR and balance. No meaningful predictions could be made using LRI and WR as dependent variables. Discussion: The results suggest that at self-selected speed, the decrease in speed itself is sufficient to compensate for the age-related decline in the motor functions tested; by contrast, lowering the WR is required at maximal speed, presumably to prevent imbalance. Therefore, any excessive lowering of LRI and WR indicates loss of homeostasis of walking mechanics and invites diagnostic investigation.

Effects of Postactivation Performance Enhancement on The Vertical Jump in High-Level Volleyball Athletes.

The objective of this study was to evaluate the effects of a training session with and without an intervention of postactivation performance enhancement (PAPE) on countermovement jump (CMJ) height, perceived recovery status (PRS), and ratings of perceived exertion (RPEs), followed by a specific volleyball training session. The sample consisted of sixteen professional male volleyball players, with an average age of 26.8±6.1 years and average height of 195.9±6.7 cm, randomly divided into a group with PAPE intervention (GPAPE) (n=8), and a control group (CTRL) without PAPE intervention (n=8). The control group carried out the training session with plyometric exercises, and the GPAPE added conditioning protocols for PAPE to plyometric training, followed by a technical tactical volleyball session. At the end of the training session, there was an increase of 16.3% in the height of the CMJ in the GPAPE, while the CTRL showed a decrease of 5% in the height of the CMJ. PRS and RPE variables did not differ between the groups. It was concluded that PAPE had a positive effect on the height of the vertical jump after plyometric training, which was maintained until the end of the technical and tactical volleyball session.

Can Prolongate Use of Social Media Immediately Before Training Worsen High Level Male Volleyball Players' Visuomotor Skills?

Our aim was to analyze the effect of mental fatigue caused by prolonged social media use on high-level volleyball players' visuomotor skills. Eighteen high-level male young volleyball players participated in this randomized, counterbalanced, crossover design. All participants underwent a 2-week experiment in which we measured their response times when performing a visuomotor task with and without mental fatigue inducement through repeated use of social media immediately before training sessions. In the control condition, participants watched TV for 30-minutes, and in the social media condition, they used a social media app (Instagram®) on smartphones for 30-minutes. We found a significant Condition x Time interaction on visuomotor task response time (p = 0.03), but there was no significant main effect of either Time or Condition. Mental fatigue, induced by repeated app-based social media use for 30-minutes immediately before training sessions, affected elite male volleyball players' visuomotor skills.

Relationship between vertical jumping ability and endurance capacity with internal training loads in professional volleyball players during preseason.

BACKGROUND: This study aimed to quantify internal training load and changes in vertical jumping ability and endurance capacity of professional volleyball players during the preseason, and to explore relationships between players' physical qualities at the beginning of the preseason with internal training load accumulated during the first two weeks of training. METHODS: Sixteen male professional volleyball players from a team participating in the Brazilian National Super League took part in the study. Before and after a 10-week preseason, their vertical jumping ability and endurance capacity were assessed by squat jump, countermovement jump without and with arm swing, and YoYo endurance test, level 1. The internal training load was quantified by the session rating of perceived exertion method. Results were analyzed using analysis of variance, magnitude-based inference and Pearson's correlation. RESULTS: The internal training load varied between 1388±111 arbitrary units (a.u.) and 3852±149 a.u., and performance in all the tests was positively changed (small to moderate effect sizes) at end of preseason training. Significant (P<0.05) very large and large correlations were observed between squat jump (r=-0.81) and YoYo endurance test (r=-0.64) performances and internal training load accumulated during the first two training weeks, respectively. CONCLUSIONS: The internal training load and training strategies undertaken by the investigated team were effective to improve players' vertical jumping ability and endurance capacity. Coaches need to improve these physical qualities of volleyball players in order to improve their tolerance to training.

Jump performance and mechanics after a regular training bout in elite volleyball players.

BACKGROUND: Volleyball is a complex intermittent sport characterized by short explosive technical movements, many of which involve vertical jumping. The assessment of mechanical jumping variables in relation to both injury prevention and performance enhancement through the use of wearable technologies is becoming a new training tool among professional volleyball players. METHODS: The present study aimed to assess the vertical jumping mechanics before and after a controlled load (volume and intensity) of a routine volleyball training session among male professional players. Twelve male elite professional volleyball players (23.7±4.9 years, 198.1±6.2 cm, 92.2±10.3 kg) of national and international level belonging to the same Brazilian first league team were recruited. Biomechanical analysis of vertical unilateral countermovement jump (CMJ) and bilateral CMJ tests were performed before and after a routine training session of these players at their usual training court. An inertial orientation sensor placed at the third lumbar vertebra was employed for biomechanical data collection. RESULTS: In relation to the unilateral CMJ, a 10% decrease (P=0.02) in the vertical ground reaction force after training compared to pretraining values was observed. However, no significant differences were observed in the remaining outcomes. Regarding the bilateral CMJ, no significant differences were observed in all assessed outcomes. CONCLUSIONS: Our findings showed no evidence of fatigue after a controlled regular in season volleyball training session in professional players. In addition, this volleyball training session induced a significant reduction in the vertical ground reaction force during unilateral CMJ in volleyball players.

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.

Factors influencing self-selected walking speed in fibrotic interstitial lung disease.

This study aimed to investigate the walking economy and possible factors influencing self-selected walking speed (SSWS) in patients with fibrotic interstitial lung disease (ILD) compared to controls. In this study, 10 patients with ILD (mean age: 63.8 ± 9.2 years, forced expiratory volume in the first second: 56 ± 7% of predicted) and 10 healthy controls underwent resting pulmonary function tests, cardiopulmonary exercise, and submaximal treadmill walking tests at different speeds. The walking economy was assessed by calculating the cost-of-transport (CoT). Dynamic stability was assessed by stride-to-stride fluctuations using video recordings. Patients with ILD showed reduced peak oxygen uptake with a tachypneic breathing pattern and significant oxygen desaturation during exercise. The CoT did not differ between the groups (p = 0.680), but dyspnea and SpO2 were higher and lower, respectively, in patients with ILD at the same relative speeds. SSWS was reduced in ILD patients (2.6 ± 0.9 vs. 4.2 ± 0.4 km h-1 p = 0.001) and did not correspond to the energetically optimal walking speed. Dynamic stability was significantly lower in patients with ILD than in healthy controls, mainly at lower speeds. Patients with ILD presented a similar cost of transport compared to healthy controls; however, they chose lower SSWS despite higher walking energy expenditure. Although walking stability and dyspnea were negatively affected, these factors were not associated with the slower walking speed chosen by individuals with ILD.

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.

Responses to progressive exercise in subjects with chronic dyspnea and inspiratory muscle weakness.

INTRODUCTION: Inspiratory muscle weakness (IMW) is a potential cause of exertional dyspnea frequently under-appreciated in clinical practice. Cardiopulmonary exercise testing (CPET) is usually requested as part of the work-up for unexplained breathlessness, but the specific pattern of exercise responses ascribed to IMW is insufficiently characterized. OBJECTIVES: To identify the physiological and sensorial responses to progressive exercise in dyspneic patients with IMW without concomitant cardiorespiratory or neuromuscular diseases. METHODS: Twenty-three subjects (18 females, 55.2 ± 16.9 years) complaining of chronic daily life dyspnea (mMRC = 3 [2-3]) plus maximal inspiratory pressure < the lower limit of normal and 12 matched controls performed incremental cycling CPET. FEV1/FVC<0.7, significant abnormalities in chest CT or echocardiography, and/or an established diagnosis of neuromuscular disease were among the exclusion criteria. RESULTS AND CONCLUSION: Patients presented with reduced aerobic capacity (peak V̇O2: 79 ± 26 vs 116 ± 21 %predicted), a tachypneic breathing pattern (peak breathing frequency/tidal volume = 38.4 ± 22.7 vs 21.7 ± 14.2 breaths/min/L) and exercise-induced inspiratory capacity reduction (-0.17 ± 0.33 vs 0.10 ± 0.30 L) (all P < .05) compared to controls. In addition, higher ventilatory response (ΔV̇E/ΔV̇CO2 = 34.1 ± 6.7 vs 27.0 ± 2.3 L/L) and symptomatic burden (dyspnea and leg discomfort) to the imposed workload were observed in patients. Of note, pulse oximetry was similar between groups. Reduced aerobic capacity in the context of a tachypneic breathing pattern, inspiratory capacity reduction and preserved oxygen exchange during progressive exercise should raise the suspicion of inspiratory muscle weakness in subjects with otherwise unexplained breathlessness.

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.

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.

Physiological Predictors of Maximal Incremental Running Performance.

PURPOSE: The aim of this study was to verify whether physiological components [vertical jumps (Squat Jump - SJ and Countermovement Jump - CMJ), eccentric utilization ratio (EUR) of vertical jumps, running economy (RE), metabolic cost (C MET ), first and second ventilatory threshold (VT1 and VT2) maximal oxygen uptake (VO2MAX)] can predict maximal endurance running performance. METHODS: Twenty male runners performed maximal vertical jumps, submaximal running at constant speeds, and maximal incremental running test. Before, we measured anthropometric parameters (body mass and height) and registered the training history and volume. SJ and CMJ tests were evaluated prior to running tests. Initially, the oxygen uptake (VO2) was collected at rest in the orthostatic position for 6 min. Soon after, a 10-min warm-up was performed on the treadmill at 10 km⋅h-1, followed by two 5-min treadmill rectangular tests at 12 and 16 km⋅h-1 monitored by a gas analyzer. After that, the runners performed a maximal incremental test, where the VT1, VT2, and VO2MAX were evaluated, as well as the maximum running speed (vVO2MAX). Thus, RE and C MET were calculated with data obtained during rectangular running tests. Multivariate stepwise regression analyses were conducted to measure the relationship between independent variables (height and power of SJ and CMJ, EUR; RE and C MET 12 and 16 km⋅h-1 ; VT1, VT2, and VO2MAX), as predictors of maximal running performance (vVO2MAX), with significance level at α = 0.05. RESULTS: We found that VO2MAX and RE at 16 km⋅h-1 predict 81% of performance (vVO2MAX) of endurance runners (p < 0.001). CONCLUSION: The main predictors of the maximal incremental running test performance were VO2MAX and RE.

Mechanical and energetic determinants of impaired gait following stroke: segmental work and pendular energy transduction during treadmill walking.

Systems biology postulates the balance between energy production and conservation in optimizing locomotion. Here, we analyzed how mechanical energy production and conservation influenced metabolic energy expenditure in stroke survivors during treadmill walking at different speeds. We used the body center of mass (BCoM) and segmental center of mass to calculate mechanical energy production: external and each segment's mechanical work (Wseg). We also estimated energy conservation by applying the pendular transduction framework (i.e. energy transduction within the step; Rint). Energy conservation was likely optimized by the paretic lower-limb acting as a rigid shaft while the non-paretic limb pushed the BCoM forward at the slower walking speed. Wseg production was characterized by greater movements between the limbs and body, a compensatory strategy used mainly by the non-paretic limbs. Overall, Wseg production following a stroke was characterized by non-paretic upper-limb compensation, but also by an exaggerated lift of the paretic leg. This study also highlights how post-stroke subjects may perform a more economic gait while walking on a treadmill at preferred walking speeds. Complex neural adaptations optimize energy production and conservation at the systems level, and may fundament new insights onto post-stroke neurorehabilitation.This article has and associated First Person interview with the first author of the paper.

Factors Affecting Training and Physical Performance in Recreational Endurance Runners.

Endurance running has become an immensely popular sporting activity, with millions of recreational runners around the world. Despite the great popularity of endurance running as a recreational activity during leisure time, there is no consensus on the best practice for recreational runners to effectively train to reach their individual objectives and improve physical performance in a healthy manner. Moreover, there are lots of anecdotal data without scientific support, while most scientific evidence on endurance running was developed from studies observing both recreational and professional athletes of different levels. Further, the transference of all this information to only recreational runners is difficult due to differences in the genetic predisposition for endurance running, the time available for training, and physical, psychological, and physiological characteristics. Therefore, the aim of this review is to present a selection of scientific evidence regarding endurance running to provide training guidelines to be used by recreational runners and their coaches. The review will focus on some key aspects of the training process, such as periodization, training methods and monitoring, performance prediction, running technique, and prevention and management of injuries associated with endurance running.

The Entrainment Frequency of Cardiolocomotor Synchronization in Long-Distance Race Emerges Spontaneously at the Step Frequency.

In forced conditions, where the heart rate and step frequency have been matched, cardiolocomotor synchronization (CLS) has been recognized. However, knowledge about the occurrence of CLS and its triggers in sports gesture in real contexts is little known. To address this gap, the current study tested the hypothesis that CLS in running spontaneous conditions would emerge at entrainment bands of muscle activation frequencies associated with a freely chosen step frequency. Sixteen male long-distance runners undertook treadmill assessments running ten three-minute bouts at different speeds (7, 7.5, 8, 9, 10, 11, 12, 13, 14, and 15 km⋅h-1). Electrocardiography and surface electromyography were recorded simultaneously. The center frequency was the mean of the frequency spectrum obtained by wavelet decomposition, while CLS magnitude was determined by the wavelet coherence coefficient (WCC) between the electrocardiography and center frequency signals. The strength of CLS affected the entrainment frequencies between cardiac and muscle systems, and for WCC values greater than 0.8, the point from which we consider the emerging CLS, the entrainment frequency was between 2.7 and 2.8 Hz. The CLS emerged at faster speeds (13-15 km⋅h-1) most prevalently but did not affect the muscle activation bands. Spontaneous CLS occurred at faster speeds predominantly, and the entrainment frequencies matched the locomotor task, with the entrainment bands of frequencies emerging around the step frequencies (2.7-2.8 Hz). These findings are compatible with the concept that interventions that determine optima conditions of CLS may potentiate the benefits of the cardiac and muscle systems synchronized in distance runners.

Effects of Nordic walking training on quality of life, balance and functional mobility in elderly: A randomized clinical trial.

PURPOSE: There is physiological and biomechanical evidence suggesting a possible advantage of using poles in walking training programs. The purpose of this proof-of-concept study was to test the hypothesis that untrained elderly training Nordic walking for eight weeks will show higher improvements on the functional mobility, quality of life and postural balance than that training without poles; more likely to occur in self-selected walking speed (primary outcome), and the locomotor rehabilitation index than the quality of life, the static balance and the dynamic stability. It was a two-arm randomized sample- and load-controlled study. METHODS: Thirty-three untrained older people were randomly assigned into Nordic walking (n = 16, age: 64.6±4.1 years old) and free walking (n = 17, age: 68.6±3.9 years old) training groups. RESULTS: Improvements in the self-selected walking speed (primary outcome, p = 0.011, ES = 0.42 95%CI -0.31 to 1.16), locomotor rehabilitation index (p = 0.013, ES = 0.36; (95%CI -0.39 to 1.10), quality of life (p<0.05), static balance (p<0.05) and dynamic variability (p<0.05) were found in both groups. CONCLUSIONS: The hypothesis was not supported, our findings indicated that after 8 weeks, the Nordic walking training did not result in greater improvements than free walking training for the primary outcome (self-selected walking speed) and most of the secondary outcomes (including locomotor rehabilitation index, static balance, dynamic stability, and psychological and social participation domains of quality of life). TRIAL REGISTRATION: ClinicalTrials.gov NCT03096964.

Pilates training improves 5-km run performance by changing metabolic cost and muscle activity in trained runners.

PURPOSE: Strength training improves distance running economy and performance. This finding is based predominantly on maximal and explosive strength programmes applied to locomotor muscles, particularly on the lower limbs. It is not certain whether a minimization of metabolic cost (Cmet) and an improvement in running performance is feasible with strength training of the postural and trunk muscles. METHODS: Using kinematic, neuromuscular and metabolic measurements of running at two different speeds before and after a 12-week Pilates training programme, we tested the hypothesis that core training might improve the running Cmet and performance of trained runners. Thirty-two individuals were randomly assigned to the control group (CG, n = 16) or the Pilates group (PG, n = 16). RESULTS: Confirming our hypothesis, a significant improvement (p<0.05) was observed for running performance in the PG (pre: 25.65±0.4 min; post: 23.23±0.4 min) compared to the CG (pre: 25.33±0.58 min; post: 24.61±0.52 min). Similarly, the PG (4.33±0.07 J.kg-1.m-1) had better responses than the CG (4.71±0.11 J.kg-1.m-1) during post-training for Cmet. These findings were accompanied by decreased electromyographic activity of the postural muscles at submaximal running intensities in the PG. CONCLUSIONS: Overall, these results provide a rationale for selecting strength training strategies that target adaptations on specific postural and locomotor muscles for trained distance runners.

Effects of load carriage on physiological determinants in adventure racers.

Adventure racing athletes need run carrying loads during the race. A better understanding of how different loads influence physiological determinants in adventure racers could provide useful insights to gauge training interventions to improve running performance. We compare the maximum oxygen uptake (VO2max), the cost of transport (C) and ventilatory thresholds of twelve adventure running athletes at three load conditions: unloaded, 7 and 15% of body mass. Twelve healthy men experienced athletes of Adventure Racing (age 31.3 ± 7.7 years, height 1.81 ± 0.05 m, body mass 75.5 ± 9.1 kg) carried out three maximal progressive (VO2max protocol) and three submaximal constant-load (running cost protocol) tests, defined in the following quasi-randomized conditions: unloaded, 7% and, 15% of body mass. The VO2max (unload: 59.7 ± 5.9; 7%: 61.7 ± 6.6 and 15%: 64.6 ± 5.4 ml kg-1 min-1) did not change among the conditions. While the 7% condition does neither modify the C nor the ventilatory thresholds, the 15% condition resulted in a higher C (5.2 ± 0.9 J kg-1 m-1; P = 0.001; d = 1.48) than the unloaded condition (4.0 ± 0.7 J kg-1 m-1). First ventilatory threshold was greater at 15% than control condition (+15.5%; P = 0.003; d = 1.44). Interestingly, the velocities on the severe-intensity domain (between second ventilatory threshold and VO2max) were reduced 1% equivalently to 1% increasing load (relative to body mass). The loading until 15% of body mass seems to affect partially the crucial metabolic and ventilatory parameters, specifically the C but not the VO2max. These findings are compatible with the concept that interventions that enhance running economy with loads may improve the running performance of adventure racing's athletes.

Aspectos biomecânicos da locomoção de pessoas com doença de Parkinson: revisão narrativa / Biomechanical aspects of locomotion people with Parkinson's disease: review study / Aspectos biomecánicos de la locomoción de personas con enfermedad de Parkinson: una revisión

Resumo A presente revisão narrativa tem por objetivo analisar os aspectos biomecânicos da locomoção e os efeitos de intervenções nos padrões da marcha de pessoas com doença de Parkinson (DP). Fez-se uma pesquisa bibliográfica no banco de dados dos sistemas SciELO e PubMed, com as seguintes palavras: human locomotion, biomechanics, pathologic gait e Parkinson's disease, em periódicos nacionais e internacionais. Concluímos que as principais alterações biomecânicas são nos parâmetros espaçotemporais, como menor comprimento de passada e estabilidade dinâmica, além da baixa ativação muscular nos músculos propulsores, bem como menor velocidade autosselecionada da marcha. Fazem-se necessários protocolos de treinamento de caminhada que considerem esses parâmetros para auxiliar a reabilitação da marcha de pessoas com DP.

Abstract The purpose of this review was to analyze the biomechanical aspects of walking in individuals with Parkinson's disease (PD), as well as to examine the effects of intervention on gait pattern of PD. We carried out a bibliographic search on electronic databases SciELO and PubMed, using the following words: human locomotion, biomechanics, pathologic gait e Parkinson's disease, in national and international scientific journals. The main alterations on walking biomechanics are related to spatiotemporal parameters, lower stride length and dynamical stability, as well as reduced electromyographic activation on propulsion muscles and lower self-selected speed. These outcomes seem to be important targets in walking training protocols for rehabilitation of gait in PD.

Resumen La presente revisión tiene por objetivo analizar los aspectos biomecánicos de la locomoción y los efectos de las intervenciones en los patrones de la marcha en personas con enfermedad de Parkinson (EP). Se realizó una investigación bibliográfica en las bases de datos SciELO y PubMed, utilizando las siguientes palabras:human locomotion, biomechanics, pathologic gait y Parkinson's disease, en revistas nacionales e internacionales indexadas. Se llegó a la conclusión de que las principales alteraciones biomecánicas se encuentran en los parámetros espacio-temporales, como menor longitud de la zancada y estabilidad dinámica, además de una baja activación electromiográfica de los músculos propulsores, como menor velocidad autoseleccionada de la marcha. Estos resultados convierten en necesarios protocolos de entrenamiento de la marcha que tengan en cuenta estos parámetros para la rehabilitación de personas con EP.

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.