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BACKGROUND: The goal of this study was to verify whether anthropometric, physiological and neuromuscular factors, as well as training characteristics, could predict cycling performance during maximal incremental and time-to-exhaustion tests. METHODS: Twenty cyclists were evaluated: Anthropometric variables, knee extensor muscle activation and architecture, training history, and training volume were assessed. Second ventilatory threshold (VT
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Rendimiento Atlético , Ciclismo , Consumo de Oxígeno , Humanos , Ciclismo/fisiología , Masculino , Adulto , Rendimiento Atlético/fisiología , Consumo de Oxígeno/fisiología , Prueba de Esfuerzo , Músculo Esquelético/fisiología , Antropometría , Músculo Cuádriceps/fisiología , Adulto JovenRESUMEN
Structural alterations of the triceps surae and Achilles tendon (AT) can promote plantarflexion weakness one-year following an AT repair, influencing the activation strategies of the Gastrocnemius Medialis (GM) muscle. However, this is yet to be demonstrated. We aimed to determine whether patients with plantar flexion weakness one-year after AT repair show altered GM spatial activation. In this cross-sectional and case-control study, ten middle-aged men (age 34 ± 7 years old, and 12.9 ± 1.1 months post-surgery) with a high AT total rupture score who attended conventional physiotherapy for six months after surgery, and ten healthy control men (age 28 ± 9 years old), performed maximal and submaximal (40, 60 and 90%) voluntary isometric plantarflexion contractions on a dynamometer. The peak plantar flexor torque was determined by isokinetic dynamometry and the GM neuromuscular activation was measured with a linear surface-electromyography (EMG) array. Overall EMG activation (averaged channels) increased when the muscle contraction levels increased for both groups. EMG spatial analysis in AT repaired group showed an increased activation located distally at 85-99%, 75-97%, and 79-97% of the electrode array length for 40%, 60%, and 90% of the maximal voluntary isometric contractions, respectively. In conclusion, patients with persistent plantar flexion weakness after AT rupture showed higher distal overactivation in GM.
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Tendón Calcáneo , Traumatismos del Tobillo , Traumatismos de los Tendones , Masculino , Persona de Mediana Edad , Humanos , Adulto , Adulto Joven , Tendón Calcáneo/cirugía , Tendón Calcáneo/fisiología , Estudios de Casos y Controles , Estudios Transversales , Articulación del Tobillo/fisiología , Músculo Esquelético/fisiología , Electromiografía , Contracción Isométrica/fisiologíaRESUMEN
ABSTRACT: Glänzel, MH, Rodrigues, DR, Petter, GN, Pozzobon, D, Vaz, MA, and Geremia, JM. Foam rolling acute effects on myofascial tissue stiffness and muscle strength: a systematic review and meta-analysis. J Strength Cond Res 37(4): 951-968, 2023-Foam rolling (FR) is widely used in rehabilitation and physical training. However, the effects of FR on myofascial tissue stiffness and muscle strength remain unclear. This study aimed to perform a systematic review with meta-analysis of trials that tested the FR acute effects during warm-up on the myofascial tissue stiffness and muscle strength in healthy adults or athletes. This systematic review (CRD42021227048) was performed according to Cochrane's recommendations, with searches performed in PubMed, Web of Science, Embase, and PEDro databases. Syntheses of included studies' data were performed, and the PEDro scale was used to assess the methodological quality of the studies. Certainty of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluations approach. Twenty included studies assessed trunk and thigh fascial tissue stiffness, and thigh and calf muscle stiffness, whereas muscle strength was assessed in the knee extensors and flexors, and plantar flexors muscles. Qualitative analysis showed decreases in fascial ( n = 2) and muscle ( n = 5) stiffness after FR. However, the meta-analysis showed no effects of FR on myofascial tissue stiffness. Both qualitative and quantitative analyses showed no effects of FR on isometric muscle strength, eccentric torque, and rate of force development. However, the knee extensor concentric torque increased after FR. Foam rolling increases the knee extensor concentric torque, but it does not acutely change the myofascial tissue stiffness and isometric muscle strength. However, evidence of these studies provides low certainty to state that FR does not change these parameters. Therefore, high methodological quality studies should be performed to better ascertain the effects of FR on the myofascial tissue stiffness and muscle strength.
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Rodilla , Músculo Esquelético , Adulto , Humanos , Músculo Esquelético/fisiología , Rodilla/fisiología , Articulación de la Rodilla/fisiología , Extremidad Inferior , Fuerza Muscular/fisiología , Rango del Movimiento Articular/fisiologíaRESUMEN
OBJECTIVE: To verify the effects of replacing exercises targeted on core/hip muscles by exercises targeted on leg/foot muscles in a rehabilitation program for patellofemoral pain (PFP). DESIGN: Randomized Controlled Trial. PARTICIPANTS: Fifty women with PFP. METHODS: PFP participants were randomized into the standard rehabilitation group (SRG, n = 25) or distal exercise group (DEG, n = 25). Knee pain, patient-reported function, dynamic knee valgus and muscle strength were measured at baseline and after six and twelve weeks of the program start. RESULTS: SRG and DEG presented similar responses to rehabilitation (except for muscle strengthening). Knee pain reduced after 6 weeks (SRG: -37.7%, ES = 1.23; DEG: -30%, ES = 0.93) and 12 weeks (SRG: -47.4%, ES = 1.53; DEG: -43.3%, ES = 1.46). Patient-reported function improved after 6 weeks (SRG: +7.3%, ES = 0.45; DEG: +3.8%, ES = 0.22) and 12 weeks (SRG: +14.1%, ES = 0.80; DEG: +8.8%, ES = 0.50). Dynamic knee valgus reduced after 12 weeks (SRG: -29.7%, ES = 0.38; DEG: -34.5%, ES = 0.32). Both groups experienced increases in knee extension strength (SRG: +9%, ES = 0.28; DEG: +6%, ES = -0.29), but only SRG had strength gains for hip abduction (+10%, ES = 0.36) and extension (+11%, ES = 0.44). CONCLUSION: Exercises targeted on core/hip muscles can be replaced by exercises targeted on leg/foot muscles in a lower limb exercise-based rehabilitation program for women with PFP. CLINICAL TRIAL REGISTRATION: NCT03663595.
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Síndrome de Dolor Patelofemoral , Femenino , Humanos , Pierna , Fuerza Muscular/fisiología , Terapia por Ejercicio , Músculo Esquelético , Extremidad Inferior , DolorRESUMEN
BACKGROUND: The mechanical energy required to drive the cranks during cycling depends on concentric and eccentric muscle actions. However, no study to date provided clear evidence on how workload levels affect concentric and eccentric muscle actions during cycling. Therefore, the aim of this study was to investigate the workload effects on the timing of lower limb concentric and eccentric muscle actions, and on joint power production. METHODS: Twenty-one cyclists participated in the study. At the first session, maximal power output (PO
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Contracción Muscular , Carga de Trabajo , Ciclismo/fisiología , Electromiografía , Humanos , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Músculo Cuádriceps/fisiologíaRESUMEN
INTRODUCTION: The aim of this study was to evaluate the intra and inter-rater and inter-analyzer reliability of neuromuscular variables and functional tests. METHODS: Cross-sectional crossover design. Two independent raters and analyzers evaluated twenty-two healthy subjects. Knee-extensor strength was assessed from three maximal voluntary isometric contractions. Muscle activation was obtained from the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) muscles. VL and RF muscles' architecture [fascicle length (FL), pennation angle (PA), muscle thickness (MT)] was obtained at rest by ultrasound. The time from five sit-to-stand (STS) trials, and the distance from the 6-min walk test (6MWT) were obtained. Intraclass correlation coefficient was determined and classified as strong (r = 0.75-1.00), moderate (r = 0.40-0.74), and weak (r < 0.40). RESULTS: Strong intra-rater reliability values were observed for strength (r = 0.97), muscle activation [VL (r = 0.91); RF (r = 0.92); VM (r = 0.80)], VL [FL (r = 0.90); PA (r = 0.94); MT (r = 0.99)] and RF [MT (r = 0.85)] muscle architecture, STS (r = 0.95), and 6MWT (r = 0.98). Inter-rater reliability also presented strong values for strength (r = 0.97), muscle activation [VL (r = 0.94); RF (r = 0.79); VM (r = 0.78)], muscle architecture VL [PA (r = 0.81) and MT (r = 0.88)] and RF [MT (r = 0.80)], STS (r = 0.93), and 6MWT (r = 0.98). A moderate correlation VL muscle architecture [FL (r = 0.69)]. Inter-analyzer muscle architecture reliability presented strong VL [FL (r = 0.77); PA (r = 0.76); MT (r = 0.91)] and RF [MT (r = 0.99)]. CONCLUSION: The high intra and inter-rater and inter-analyzer reliability values for most variables is evidence that they can be used for clinical evaluation. Muscle architecture might need a longer training period by different raters and analyzers to increase reliability.
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Articulación de la Rodilla , Rodilla , Estudios Transversales , Electromiografía , Humanos , Articulación de la Rodilla/diagnóstico por imagen , Músculo Esquelético , Músculo Cuádriceps/diagnóstico por imagen , Reproducibilidad de los ResultadosRESUMEN
Neuromuscular electrical stimulation (NMES) applied to skeletal muscles is an effective rehabilitation and exercise training modality. However, the relatively low muscle force and rapid muscle fatigue induced by NMES limit the stimulus provided to the neuromuscular system and subsequent adaptations. We hypothesize that adaptations to NMES will be enhanced by the use of specific stimulation protocols and adjuvant interventions.
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Adaptación Fisiológica , Fatiga Muscular , Estimulación Eléctrica , Ejercicio Físico , Humanos , Músculo EsqueléticoRESUMEN
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.
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Terapia por Luz de Baja Intensidad , Resistencia Física/efectos de la radiación , Carrera/fisiología , Adulto , Estudios Cruzados , Método Doble Ciego , Metabolismo Energético/efectos de la radiación , Prueba de Esfuerzo , Humanos , Masculino , Consumo de Oxígeno , Percepción/efectos de la radiación , Esfuerzo Físico/efectos de la radiaciónRESUMEN
ABSTRACT The aim of this study was to review the literature on the effects of muscle fatigue generated by different cycling protocols, on the kinetics and kinematics of the crank cycle. Twenty-two studies were included in the review. The establishment of the fatigue processes caused an increase in the resulting and effective forces (all tests), together with the pedaling efficiency (incremental and constant tests). In addition, fatigue caused joint changes in the lower limbs (increased range of motion in the ankle and reduced contribution to total torque) in different cycling tests. Therefore, these pedaling strategies may be related to the maintenance of muscle work to postpone the cyclists' exhaustion.
RESUMO O objetivo deste estudo foi revisar a literatura sobre os efeitos da fadiga muscular gerada por diferentes protocolos de ciclismo, sobre a cinética e cinemática do ciclo de pedalada. Vinte e dois estudos foram incluídos na revisão. A instauração dos processos de fadiga provocou aumento das forças resultante e efetiva (todos os testes), em conjunto com a eficiência de pedalada (testes incremental e constante). Além disso, a fadiga provocou mudanças articulares dos membros inferiores (aumento da amplitude articular do tornozelo e redução da sua contribuição para o torque total), em diferentes testes de ciclismo. Estas estratégias de pedalada podem estar relacionadas à manutenção do trabalho muscular para postergar a exaustão dos ciclistas.
RESUMEN El objetivo de este estudio fue revisar la literatura sobre los efectos de la fatiga muscular generada por diferentes protocolos de ciclismo, sobre la cinética y cinemática del ciclo de pedaleo. Veintidós estudios se incluyeron en la revisión. El establecimiento de los procesos de fatiga provocó un aumento de las fuerzas resultantes y efectivas (todas las pruebas), junto con la eficiencia del pedaleo (prueba incremental y constante). Además, la fatiga provocó cambios articulares en los miembros inferiores (mayor rango de movimiento en el tobillo y menor contribución al torque total) en diferentes pruebas de ciclismo. Estas estrategias de pedaleo pueden estar relacionadas con el mantenimiento del trabajo muscular para posponer el agotamiento de los ciclistas.
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Studies have suggested that older individuals are more fatigable than young adults when power loss, measured during single-joint contractions, is considered the fatigue index; however, age-related differences in fatigue considering power measurements during multi-joint movements (e.g., cycling) have not been fully elucidated yet. This study examined age-related differences in dynamic and isometric measures of fatigue in response to three cycling exercises. Ten young (27⯱â¯4â¯years) and ten old (74⯱â¯4â¯years) men performed exercises on different days, 30-s Wingate, 10-min at severe-intensity, and 90-min at moderate-intensity. Dynamic measures-maximal power, torque, and velocity-were assessed after cycling and during recovery (1-8â¯min post-exercise) through 7-s cycling sprints and isometric force and fatigue etiology (central and peripheral components) through isometric contractions. There were no age-related differences in the relative reduction of dynamic and isometric measures following the Wingate and moderate-intensity tasks. Maximal power, isometric force, and indices of peripheral function (e.g., high-frequency doublet) decreased more in young compared with older individuals after the severe-intensity exercise (all pâ¯<â¯.05). The only observed age-related difference in the recovery of NM fatigue was a slower recovery of power and torque from 1 to 8â¯min (pâ¯<â¯.05) and at 4â¯min (pâ¯=â¯.015), respectively, in younger males after the Wingate. Age-related fatigue and recovery depend on the fatiguing exercise intensity and duration and on the fatigue assessment mode. This study provides novel information on age-related neuromuscular fatigue responses to multi-joint dynamic exercises performed at different intensities and durations.
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Fatiga Muscular , Músculo Esquelético , Electromiografía , Ejercicio Físico , Humanos , Contracción Isométrica , Masculino , TorqueRESUMEN
Lanferdini, FJ, Manganelli, BF, Lopez, P, Klein, KD, Cadore, EL, and Vaz, MA. Echo intensity reliability for the analysis of different muscle areas in athletes. J Strength Cond Res 33(12): 3353-3360, 2019-Skeletal muscles' echo intensity (EI) is used as a parameter to evaluate muscle damage and muscle quality after exercise or training. However, recent muscle EI studies have used regions of interest (ROIs) of different sizes for assessing muscle damage and muscle quality, which may lead to different results if the different ROIs from the same muscle are not reliable. Although a maximum rectangular ROI (RET-ROI), included in the muscles' anatomical cross-sectional area, can be used to represent the maximum muscle ROI (MAX-ROI), no studies were found that investigated the reliability of the evaluations of different ROIs for the EI of superficial vs. deep muscles of the thigh. In addition, no studies have evaluated different ROIs in cyclists, at different days and analyzed by different raters. The aim of this study was to evaluate the EI reliability of rectus femoris (RF) and vastus intermedius (VI) muscles of cyclists. Twenty cyclists visited the laboratory 4 times for the evaluation of RF and VI muscles transversal ultrasound images. Echo intensity was determined from grayscale mean values by 2 examiners who performed the analysis with 3 different ROIs: MAX-ROI, RET-ROI, and 1-cm ROI (1CM-ROI). The between-ROI EI data reliability showed a strong correlation in both RF (r ≥ 0.79) and VI (r ≥ 0.87) muscles. Bland-Altman tests demonstrated high agreement among RF ROI muscle areas (p > 0.05), with no agreement between the VI areas (p < 0.05). Only the RF muscle MAX-ROI, RET-ROI, and 1CM-ROI areas are similar for EI analysis, with no similarities for the same VI muscle areas.
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Músculo Cuádriceps/diagnóstico por imagen , Ultrasonografía/métodos , Adulto , Ciclismo , Humanos , Masculino , Variaciones Dependientes del Observador , Músculo Cuádriceps/patología , Reproducibilidad de los Resultados , Muslo , Adulto JovenRESUMEN
BACKGROUND: Muscular parameters have been considered to influence gait of older adults, but it is still unclear which specific lower limb muscular parameters correlate with kinematics of overground and obstacle crossing in older adults. RESEARCH QUESTION: What lower limb muscular parameters correlate and explain kinematics of overground walking and obstacle crossing ability in the elderly? METHODS: Muscle structure was evaluated in 15 older individuals (75.4⯱â¯5 years) through measures of architecture (muscle thickness, fascicle length, and pennation angle) and muscle quality (echo intensity) from lower limb muscles (vastus lateralis, biceps femoris, rectus femoris, tibialis anterior, and gastrocnemius medialis). Muscle function was assessed through isometric strength of hip, knee and ankle joint muscles. Gait kinematics (toe and heel clearances, step length and gait speed) was evaluated during walking with and without obstacle crossing at preferred and maximal gait speeds. Correlation and regression analyses were performed considering a significance level of 0.05. RESULTS: Isometric strength did not correlate with gait kinematics and gait speed. Tibialis anterior thickness correlated with lead limb toe clearance, and vastus lateralis thickness with gait speed and step length. Vastus lateralis echo intensity correlated with step length and gait speed. SIGNIFICANCE: Tibialis anterior and vastus lateralis muscles deserve attention in physical training to improve gait of older adults. Specifically, tibialis anterior should receive more attention on exercise programs aiming at improvement of obstacle crossing, and knee extensors when aiming at improving gait speed and step length.
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Marcha/fisiología , Contracción Isométrica/fisiología , Extremidad Inferior/fisiología , Músculo Esquelético/fisiología , Caminata/fisiología , Anciano , Anciano de 80 o más Años , Articulación del Tobillo/fisiología , Fenómenos Biomecánicos , Estudios Transversales , Electromiografía , Femenino , Humanos , Masculino , Músculo Esquelético/anatomía & histologíaRESUMEN
PURPOSE: The purpose of this study was to investigate the effects of photobiomodulation therapy (PBMT) combined with resistance training on knee extensors muscle mass, strength and functional capacity in elderly men. METHODS: In this randomized double-blinded placebo-controlled trial, healthy elderly men (age 60-80 years) completed 12 weeks of resistance training (2×/week) with application of placebo (n = 13) or active PBMT (n = 11) on quadriceps muscles (850 nm, 240 J per limb) before each training session. Leg press and knee extension one-repetition maximum (1RM) tests, isometric and concentric peak torques, rectus femoris (RF) and vastus lateralis (VL) muscle thickness, timed up-and-go (TUG) and chair rise-to-standing (CRS) tests were performed before and after the intervention period. RESULTS: There were significant improvements in all outcomes for both groups (p < 0.05), except for RF muscle thickness for the placebo group (p = 0.09). Large effect sizes (ES > 0.8) were observed for leg press and leg extension 1RM and CRS tests for both groups, as well as for TUG test for PBMT group. Isokinetic peak torque for both groups and TUG for placebo group had moderate increases (ES > 0.5). Muscle thicknesses and isometric peak torque had small increases (ES > 0.2) in both groups. Both null hypothesis analysis and magnitude-based inference support similar effects of PBMT and placebo treatments. CONCLUSION: Different than previously evidenced in young subjects, PBMT with the parameters used in this study did not provide any additional benefits in comparison to placebo application on muscle mass, strength and functional capacity of healthy elderly men engaged in a resistance training program.
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Terapia por Luz de Baja Intensidad/métodos , Músculo Esquelético/fisiología , Entrenamiento de Fuerza/métodos , Anciano , Anciano de 80 o más Años , Humanos , Rodilla/fisiología , Terapia por Luz de Baja Intensidad/efectos adversos , Masculino , Persona de Mediana Edad , Fuerza Muscular , Músculo Esquelético/efectos de la radiaciónRESUMEN
This study aimed to analyze the effects of Mat Pilates on isokinetic torque of the lower limbs in elderly women. Fourteen elderly women (Age 62 ± 3 yr) participated in 12 weeks of Mat Pilates training (60-min sessions, 3 times per week). Repetitions increased every 4 weeks and the difficulty of exercises progressed from beginner to intermediate and advanced. Peak torque was assessed before (week -4 and week 0, considered as a control period) and after 6 and 12 weeks of a periodized Mat Pilates intervention. The results showed significant improvements (p < 0.05) in concentric and eccentric peak torque of knee flexors muscles, hip flexor and extensor muscles after 12 weeks. Mechanical work showed significant improvement (p < 0.05) for knee extensor muscles during eccentric contractions after week 12, for hip extensor muscles during concentric contractions week 12, and for flexor muscles during concentric and eccentric contractions after week 12. We conclude that the periodization of Mat Pilates induced significant improvements in multiple isokinetic torque parameters.
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Técnicas de Ejercicio con Movimientos/métodos , Articulación de la Rodilla/fisiología , Fuerza Muscular/fisiología , Músculo Esquelético/fisiología , Torque , Anciano , Fenómenos Biomecánicos , Femenino , Humanos , Persona de Mediana Edad , Rango del Movimiento Articular/fisiología , Salud de la MujerRESUMEN
Ribeiro-Alvares, JB, Marques, VB, Vaz, MA, and Baroni, BM. Four weeks of Nordic hamstring exercise reduce muscle injury risk factors in young adults. J Strength Cond Res 32(5): 1254-1262, 2018-The Nordic hamstring exercise (NHE) is a field-based exercise designed for knee-flexor eccentric strengthening, aimed at prevention of muscle strains. However, possible effects of NHE programs on other hamstring injury risk factors remain unclear. The purpose of this study was to investigate the effects of a NHE training program on multiple hamstring injury risk factors. Twenty physically active young adults were allocated into 2 equal-sized groups: control group (CG) and training group (TG). The TG was engaged in a 4-week NHE program, twice a week, 3 sets of 6-10 repetitions; while CG received no exercise intervention. The knee flexor and extensor strength were assessed through isokinetic dynamometry, the biceps femoris long head muscle architecture through ultrasound images, and the hamstring flexibility through sit-and-reach test. The results showed that CG subjects had no significant change in any outcome. TG presented higher percent changes than CG for hamstring isometric peak torque (9%; effect size [ES] = 0.27), eccentric peak torque (13%; ES = 0.60), eccentric work (18%; ES = 0.86), and functional hamstring-to-quadriceps torque ratio (13%; ES = 0.80). The NHE program led also to increased fascicle length (22%; ES = 2.77) and reduced pennation angle (-17%; ES = 1.27) in biceps femoris long head of the TG, without significant changes on muscle thickness. In conclusion, a short-term NHE training program (4 weeks; 8 training sessions) counteracts multiple hamstring injury risk factors in physically active young adults.
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Ejercicio Físico/fisiología , Músculos Isquiosurales/fisiología , Articulación de la Rodilla/fisiología , Traumatismos de la Pierna/prevención & control , Traumatismos de los Tejidos Blandos/prevención & control , Adolescente , Adulto , Femenino , Humanos , Masculino , Fuerza Muscular/fisiología , Músculo Esquelético/fisiología , Factores de Riesgo , Torque , Adulto JovenRESUMEN
Some evidence supports that low-level laser therapy (LLLT) reduces neuromuscular fatigue, so incrementing sports performance. A previous randomized controlled trial of our group showed increased exercise tolerance in male competitive cyclists treated with three different LLLT doses (3, 6, and 9 J/diode; or 135, 270, and 405 J/thigh) before time-to-exhaustion cycling tests. Now, the present study was designed to evaluate the effects of these LLLT doses on the VO2 kinetics of athletes during cycling tests. Twenty male competitive cyclists (29 years) participated in a crossover, randomized, double-blind, and placebo-controlled trial. On the first day, the participants performed an incremental cycling test to exhaustion to determine maximal oxygen uptake (VO2MAX) and maximal power output (POMAX), as well as a familiarization with the time-to-exhaustion test. In the following days (2 to 5), all participants performed time-to-exhaustion tests at POMAX. Before the exhaustion test, different doses of LLLT (3, 6, and 9 J/diode; or 135, 270, and 405 J/thigh, respectively) or placebo were applied bilaterally to the quadriceps muscle. All exhaustion tests were monitored online by an open-circuit spirometry system in order to analyze the VO2 amplitude, VO2 delay time, time constant (tau), and O2 deficit. Tau and O2 deficit were decreased with LLLT applications compared to the placebo condition (p < 0.05). No differences (p > 0.05) were found between the experimental conditions for VO2 amplitude and VO2 delay time. In conclusion, LLLT decreases tau and O2 deficit during time-to-exhaustion tests in competitive cyclists, and these changes in VO2 kinetics response can be one of the possible mechanisms to explain the ergogenic effect induced by LLLT.
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Ciclismo , Terapia por Luz de Baja Intensidad/métodos , Consumo de Oxígeno , Adulto , Estudios Cruzados , Método Doble Ciego , Ejercicio Físico/fisiología , Prueba de Esfuerzo , Humanos , Cinética , MasculinoRESUMEN
Evidence indicates that low-level laser therapy (LLLT) minimizes fatigue effects on muscle performance. However, the ideal LLLT dosage to improve athletes'performance during sports activities such as cycling is still unclear. Therefore, the goal of this study was to investigate the effects of different LLLT dosages on cyclists'performance in time-to-exhaustion tests. In addition, the effects of LLLT on the frequency content of the EMG signals to assess fatigue mechanisms were examined. Twenty male competitive cyclists participated in a crossover, randomized, double-blind, placebo-controlled trial. They performed an incremental cycling test to exhaustion (on day 1) followed by 4 time-to-exhaustion tests (on days 2-5) at their individual maximal power output. Before each time-to-exhaustion test, different dosages of LLLT (135, 270, and 405 J/thigh, respectively) or placebo were applied at the quadriceps muscle bilaterally. Power output and muscle activation from both lower limbs were recorded throughout the tests. Increased performance in time-to-exhaustion tests was observed with the LLLT-135 J (â¼22 s; P < .01), LLLT-270 J (â¼13 s; P = .03), and LLLT-405 J (â¼13 s; P = .02) compared to placebo (149 ± 23 s). Although LLLT-270 J and LLLT-405 J did not show significant differences in muscle activation compared with placebo, LLLT-135 J led to an increased high-frequency content compared with placebo in both limbs at the end of the exhaustion test (P ≤ .03). In conclusion, LLLT increased time to exhaustion in competitive cyclists, suggesting this intervention as a possible nonpharmacological ergogenic agent in cycling. Among the different dosages, LLLT-135 J seems to promote the best effects.
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Ciclismo/fisiología , Terapia por Luz de Baja Intensidad , Fatiga Muscular/efectos de la radiación , Resistencia Física/fisiología , Adulto , Estudios Cruzados , Método Doble Ciego , Prueba de Esfuerzo , Humanos , Masculino , Fatiga Muscular/fisiología , Músculo Cuádriceps/fisiología , Músculo Cuádriceps/efectos de la radiaciónRESUMEN
Previous studies have been limited to describe asymmetries during pedalling and suggest possible repercussion on performance and/or injury risks. However, few studies have presented strategies to mitigate asymmetries. The purpose of this study was to assess the effectiveness of a pedalling retraining intervention to reduce bilateral pedal force asymmetries. Twenty cyclists were assessed and 10 enrolled in a pedalling retraining method receiving visual and verbal feedback of pedal forces. The asymmetry index was computed for comparison of bilateral peak pedal forces and used during retraining (12 trials at 70% of peak power). Significantly larger asymmetry was observed for asymmetrical cyclists at the first three trials (P < 0.01 and ES = 1.39), which was reduced when post-retraining was compared to measures from symmetrical cyclists (P = 0.69 and ES = 0.18). Cyclists with larger asymmetry (>20%) in bilateral pedal forces reduce their asymmetries using sessions of pedalling retraining and achieve asymmetry indices similar to symmetrical cyclists.
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Rendimiento Atlético/fisiología , Ciclismo/fisiología , Extremidad Inferior/fisiología , Acondicionamiento Físico Humano/métodos , Fenómenos Biomecánicos , Retroalimentación , Humanos , MasculinoRESUMEN
OBJECTIVE: Spasticity poststroke leads to muscle weakness and soft tissue contracture, however, it is not clear how muscle properties change due this motor neural disorder. The purpose was to compare medial gastrocnemius muscle architecture and mechanical properties of the plantarflexor muscles between stroke survivors with spasticity and healthy subjects. METHODS: The study included 15 stroke survivors with ankle spasticity and 15 healthy subjects. An isokinetic dynamometer was used for the evaluation of maximal isometric plantarflexor torque and images of the medial gastrocnemius muscle were obtained using ultrasonography. Images were collected at rest and during a maximum voluntary contraction. RESULTS: The affected limb showed reduced fascicle excursion (0.9 ± 0.7 cm), shorter fascicle length, and reduced muscle thickness (0.095 ± 0.010% of leg length and 1.18 ± 0.20 cm, at rest) compared to contralateral (1.6 ± 0.4 cm, 0.106 ± 0.015% of leg length and 1.29 ± 0.24 cm, respectively) and to healthy participants (1.8 ± 0.7 cm, 0.121 ± 0.019% of leg length and 1.43 ± 0.22 cm, respectively). The contralateral limb showed lower force (between 32 and 40%) and similar architecture parameters compared to healthy participants. CONCLUSION: The affected limb had a different muscle architecture that appears to result in lower force production. The contralateral limb showed a decrease in force compared to healthy participants due to the other neural impairments than muscle morphology. Spasticity likely leds to adaptations of muscle architecture in the affected limb and in force reductions in both limbs of stroke survivors.
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Tobillo/fisiopatología , Hemiplejía/fisiopatología , Espasticidad Muscular/fisiopatología , Músculo Esquelético/patología , Músculo Esquelético/fisiopatología , Accidente Cerebrovascular/fisiopatología , Anciano , Femenino , Hemiplejía/etiología , Humanos , Masculino , Microscopía Acústica , Persona de Mediana Edad , Espasticidad Muscular/diagnóstico por imagen , Espasticidad Muscular/etiología , Músculo Esquelético/diagnóstico por imagen , Accidente Cerebrovascular/complicaciones , Sobrevivientes , TorqueRESUMEN
Humans preferentially recruit limbs to functionally perform a range of daily tasks, which may lead to performance asymmetries. Because initial training status plays an important role in the rate of progression during resistance training, could asymmetries between the preferred and nonpreferred limbs lead to different magnitudes of strengthening during a resistance training program? This issue motivated this study, in which 12 healthy and physically active men completed a 4-week control period followed by a 12-week isokinetic resistance training program, performed twice a week, including 3-5 sets of 10 maximal eccentric contractions for each limb. Every 4 weeks, knee extensor peak torques at concentric, isometric, and eccentric tests were measured using an isokinetic dynamometer and the sum of quadriceps muscle thickness was determined by ultrasound images. Before training, concentric peak torque was similar between limbs but isometric and eccentric peak torques were significantly smaller in the nonpreferred compared with the preferred limb (4.9 and 5.8%, respectively). Bilateral strength symmetry remained constant throughout the training period for concentric tests. For eccentric and isometric tests, symmetry was reached at the fourth and eighth training weeks, respectively. After 12 weeks, between-limb percent nonsignificant differences were -0.62% for isometric and -1.93% for eccentric tests. The sum of knee extensor muscle thickness had similar values before training and presented similar changes throughout the study for both the preferred and the nonpreferred limbs. In conclusion, the nonpreferred limb presents higher strength gain than the preferred limb at the initial phase of an isokinetic resistance training program, and this increased strength gain is not associated with muscle hypertrophy.