RESUMO
As soluble intercellular adhesion molecule-1 (sICAM-1) was recently hypothesized to be a key player in the mechanisms involved in exercise-induced muscular damage (EIMD), we investigated its circulating concentration changes in athletes before and after EIMD with and without the use of whole-body cryostimulation (WBC; 3â¯minâ¯at -110⯰C) at the exercise end and repeated once a day during 4 days. We previously characterized plasma specimens from 11 endurance athletes who performed twice (randomized crossover design) strenuous running leading to EIMD, followed by passive recovery or WBC. Muscle soreness and inflammatory response were observed in both cases but the use of WBC induced a significant reduction in these responses (PlosOne 2011; 6:e22748). We now found that sICAM-1 concentration slightly increased in both circumstances and remained elevated for 24â¯h (pâ¯<â¯0.01). However, no significant WBC effect was observed concerning sICAM-1 changes indicating that this compound is not a major player both in EIMD and WBC physiological impacts.
Assuntos
Crioterapia/métodos , Exercício Físico/fisiologia , Molécula 1 de Adesão Intercelular/sangue , Músculo Esquelético/lesões , Atletas , Humanos , MasculinoRESUMO
To determine if pre-cooling (PC) following heat-acclimatization (HA) can further improve self-paced endurance performance in the heat, 13 male triathletes performed two 20-km cycling time-trials (TT) at 35 °C, 50% relative humidity, before and after an 8-day training camp, each time with (PC) or without (control) ice vest PC. Pacing strategies, physiological and perceptual responses were assessed during each TT. PC and HA induced moderate (+10 ± 18 W; effect size [ES] 4.4 ± 4.6%) and very large (+28 ± 19 W; ES 11.7 ± 4.1%) increases in power output (PO), respectively. The overall PC effect became unclear after HA (+4 ± 14 W; ES 1.4 ± 3.0%). However, pacing analysis revealed that PC remained transiently beneficial post-HA, i.e., during the first half of the TT. Both HA and PC pre-HA were characterized by an enhanced PO without increased cardio-thermoregulatory or perceptual disturbances, while post-HA PC only improved thermal comfort. PC improved 20-km TT performance in unacclimatized athletes, but an 8-day HA period attenuated the magnitude of this effect. The respective converging physiological responses to HA and PC may explain the blunting of PC effectiveness. However, perceptual benefits from PC can still account for the small alterations to pacing noted post-HA.
Assuntos
Aclimatação/fisiologia , Desempenho Atlético/fisiologia , Ciclismo/fisiologia , Crioterapia/métodos , Temperatura Alta , Resistência Física/fisiologia , Adulto , Regulação da Temperatura Corporal , Estudos Cross-Over , Humanos , Gelo , Masculino , Distribuição Aleatória , Temperatura CutâneaRESUMO
Elite synchronized swimmers follow high-volume training regimen that result in elevated rates of exercise energy expenditure (ExEE). While adequate energy intake (EI) is important to optimize recovery, a number of sport-specific constraints may lead to chronically low energy availability (EA = EI-ExEE). This study aimed to quantify changes in EA, endocrine markers of energy conservation, and perceived fatigue in synchronized swimmers, during a week of baseline training followed by 4 weeks of intensified training (IT). EI, ExEE, and body composition were measured in nine swimmers at Baseline, midpoint (ITWK2 ), and end of IT (ITWK4 ). Waking saliva samples were obtained to measure [leptin]s , [ghrelin]s , and [cortisol]s . Fatigue ratings were provided daily. ExEE increased by 27% during IT. Swimmers increased EI from Baseline to ITWK2 , but decreased it significantly from ITWK2 to ITWK4 . EA, fat mass, and [leptin]s decreased from Baseline to ITWK4 , while [ghrelin]s increased significantly. Fatigue at ITWK4 was inversely correlated with Baseline EI and EA. The significant decrease in EA was accompanied by endocrine signs of energy conservation in elite swimmers. As perceived fatigue was associated with low EA, particular attention should be paid to these athletes' energy intake during phases of heavy training.
Assuntos
Ingestão de Energia , Metabolismo Energético , Fadiga/fisiopatologia , Natação/fisiologia , Atletas , Composição Corporal , Feminino , Grelina/análise , Humanos , Hidrocortisona/análise , Leptina/análise , Condicionamento Físico Humano , Saliva/química , Adulto JovemRESUMO
Exercising in the heat induces thermoregulatory and other physiological strain that can lead to impairments in endurance exercise capacity. The purpose of this consensus statement is to provide up-to-date recommendations to optimise performance during sporting activities undertaken in hot ambient conditions. The most important intervention one can adopt to reduce physiological strain and optimise performance is to heat acclimatise. Heat acclimatisation should comprise repeated exercise-heat exposures over 1-2 weeks. In addition, athletes should initiate competition and training in a euhydrated state and minimise dehydration during exercise. Following the development of commercial cooling systems (eg, cooling-vest), athletes can implement cooling strategies to facilitate heat loss or increase heat storage capacity before training or competing in the heat. Moreover, event organisers should plan for large shaded areas, along with cooling and rehydration facilities, and schedule events in accordance with minimising the health risks of athletes, especially in mass participation events and during the first hot days of the year. Following the recent examples of the 2008 Olympics and the 2014 FIFA World Cup, sport governing bodies should consider allowing additional (or longer) recovery periods between and during events, for hydration and body cooling opportunities, when competitions are held in the heat.
Assuntos
Exercício Físico/fisiologia , Temperatura Alta , Esportes/fisiologia , Aclimatação/fisiologia , Desempenho Atlético/fisiologia , Bebidas , Regulação da Temperatura Corporal/fisiologia , Vestuário , Temperatura Baixa , Exercícios de Desaquecimento/fisiologia , Desidratação/prevenção & controle , Hidratação/métodos , Transtornos de Estresse por Calor/fisiopatologia , Transtornos de Estresse por Calor/prevenção & controle , Humanos , Medicina Esportiva/métodosRESUMO
Exercising in the heat induces thermoregulatory and other physiological strain that can lead to impairments in endurance exercise capacity. The purpose of this consensus statement is to provide up-to-date recommendations to optimize performance during sporting activities undertaken in hot ambient conditions. The most important intervention one can adopt to reduce physiological strain and optimize performance is to heat acclimatize. Heat acclimatization should comprise repeated exercise-heat exposures over 1-2 weeks. In addition, athletes should initiate competition and training in a euhydrated state and minimize dehydration during exercise. Following the development of commercial cooling systems (e.g., cooling vest), athletes can implement cooling strategies to facilitate heat loss or increase heat storage capacity before training or competing in the heat. Moreover, event organizers should plan for large shaded areas, along with cooling and rehydration facilities, and schedule events in accordance with minimizing the health risks of athletes, especially in mass participation events and during the first hot days of the year. Following the recent examples of the 2008 Olympics and the 2014 FIFA World Cup, sport governing bodies should consider allowing additional (or longer) recovery periods between and during events for hydration and body cooling opportunities when competitions are held in the heat.
Assuntos
Aclimatação/fisiologia , Comportamento de Ingestão de Líquido/fisiologia , Exercício Físico/fisiologia , Transtornos de Estresse por Calor/prevenção & controle , Temperatura Alta/efeitos adversos , Esportes/fisiologia , Desempenho Atlético/fisiologia , Regulação da Temperatura Corporal/fisiologia , Desidratação/complicações , Desidratação/prevenção & controle , Desidratação/terapia , Hidratação , Transtornos de Estresse por Calor/etiologia , Transtornos de Estresse por Calor/terapia , HumanosRESUMO
This study compared the effects of a low-frequency electrical stimulation (LFES; Veinoplus(®) Sport, Ad Rem Technology, Paris, France), a low-frequency electrical stimulation combined with a cooling vest (LFESCR ) and an active recovery combined with a cooling vest (ACTCR ) as recovery strategies on performance (racing time and pacing strategies), physiologic and perceptual responses between two sprint kayak simulated races, in a hot environment (â¼32 wet-bulb-globe temperature). Eight elite male kayakers performed two successive 1000-m kayak time trials (TT1 and TT2), separated by a short-term recovery period, including a 30-min of the respective recovery intervention protocol, in a randomized crossover design. Racing time, power output, and stroke rate were recorded for each time trial. Blood lactate concentration, pH, core, skin and body temperatures were measured before and after both TT1 and TT2 and at mid- and post-recovery intervention. Perceptual ratings of thermal sensation were also collected. LFESCR was associated with a very likely effect in performance restoration compared with ACTCR (99/0/1%) and LFES conditions (98/0/2%). LFESCR induced a significant decrease in body temperature and thermal sensation at post-recovery intervention, which is not observed in ACTCR condition. In conclusion, the combination of LFES and wearing a cooling vest (LFESCR ) improves performance restoration between two 1000-m kayak time trials achieved by elite athletes, in the heat.
Assuntos
Vestuário , Temperatura Baixa , Estimulação Elétrica , Temperatura Alta/efeitos adversos , Navios , Esportes/fisiologia , Adulto , Desempenho Atlético/fisiologia , Regulação da Temperatura Corporal/fisiologia , Estudos Cross-Over , Humanos , Masculino , Percepção , Sensação Térmica , Fatores de TempoRESUMO
We investigated the changes in step temporal parameters and spring-mass behaviour during the running phase of a major international triathlon competition. 73 elite triathletes were followed during the 2011 World Championships Grand Final. The running speed, ground contact and flight times were assessed over a 30 m flat section at the beginning of the 4 running laps and towards the finish line, by using a high-frequency camera (300 Hz). The leg and vertical stiffness, and vertical displacement of the mass centre were calculated from step temporal characteristics. A concomitant decrease in running speed, vertical stiffness and leg stiffness was reported during the 4 running laps, except towards the finish line, where these parameters increased. Running biomechanics was not affected between the beginning and the end of the 10 km run, when triathletes were compared for the same running speed (1.68±0.16 m vs. 1.70±0.17 m for step length, 3.18±0.11 Hz vs. 3.16±0.15 Hz for step rate, 12.87±3.14 kN.m - 1 vs.12.76±3.05 kN.m - 1 for Kleg, 31.18±4.71 kN.m - 1 vs.30.74±3.88 kN.m - 1 for Kvert, at lap1 and finish, respectively). Multiple regression models revealed that both step rate change and step length change were correlated with running speed change and that the standardized partial regression coefficient was higher for step length change than for step rate. Independent of the cofounding effect of speed and despite the neuromuscular fatigue previously shown after long-duration events, the lower limb mechanical stiffness and the overall spring-mass regulation were not altered over the 10 km triathlon run in elite competitors. This study showed also that step length explained, to a greater extent than step frequency, the running speed variance in elite triathletes.
Assuntos
Atletas , Desempenho Atlético/fisiologia , Fadiga Muscular/fisiologia , Corrida/fisiologia , Fenômenos Biomecânicos , Comportamento Competitivo/fisiologia , Feminino , Humanos , Masculino , Análise de Regressão , Fatores de TempoRESUMO
The aim of this study was to investigate the physiological demands of Supercross BMX in elite athletes. Firstly athletes underwent an incremental cycling test to determine maximal oxygen uptake (VO2max) and power at ventilatory thresholds. In a second phase, athletes performed alone a simulated competition, consisting of 6 cycling races separated by 30 min of passive recovery on an actual BMX track. Oxygen uptake, blood lactate, anion gap and base excess (BE) were measured. Results indicated that a simulated BMX performed by elite athletes induces a high solicitation of both aerobic (mean peak VO2 (VO2peak): 94.3±1.2% VO2max) and anaerobic glycolysis (mean blood lactate: 14.5±4. 5 mmol x L(-1) during every race. Furthermore, the repetition of the 6 cycling races separated by 30 min of recovery led to a significant impairment of the acid-base balance from the third to the sixth race (mean decrease in BE: -18.8±7.5%, p<0.05). A significant relationship was found between the decrease in BE and VO2peak (r = - 0.73, p<0.05), indicating that VO2peak could explain for 54% of the variation in BMX performance. These results suggest that both oxygen-dependent and -independent fuel substrate pathways are important determinants of BMX performance.
Assuntos
Atletas , Desempenho Atlético/fisiologia , Ciclismo/fisiologia , Consumo de Oxigênio/fisiologia , Adolescente , Comportamento Competitivo , Teste de Esforço , Feminino , Glicólise/fisiologia , Humanos , Ácido Láctico/sangue , Masculino , Adulto JovemRESUMO
PURPOSE: To evaluate spring-mass (SM) behavior and associated electromyographic (EMG) activity during a run to exhaustion following a cycle exercise in trained triathletes. METHODS: Ten triathletes completed four tests: a cycling test to determine VËO(2max); a running test to determine the lactate threshold (LT); a 5 min control run at LT (C-Run) followed after a total recovery period by a cycle-to-run session to exhaustion [30 min of cycling at â¼80% VËO(2max) followed by a run until exhaustion at LT (T-Run)]. SM behavior and EMG signals in nine lower limb muscles were recorded throughout the running sessions. RESULTS: Immediately after cycling, leg stiffness was 12.1% higher than its C-Run value and a concomitant increase of EMG activity of knee extensors was observed during pre-contact. Throughout T-Run, leg stiffness decreased by 7.3%, while knee extensors and ankle flexors activities decreased during pre-contact and braking phases. No significant variations in SM parameters and no significant increase of muscle activity were reported between C-Run and the end of T-Run. CONCLUSION: SM behavior during the cycle-run test was consistent with EMG activity changes. Cessation of exercise was not associated with significant alterations of stiffness values and EMG activity.
Assuntos
Ciclismo/fisiologia , Eletromiografia , Músculo Esquelético/fisiologia , Esforço Físico/fisiologia , Corrida/fisiologia , Adulto , Atletas , Teste de Esforço , Frequência Cardíaca/fisiologia , Humanos , Ácido Láctico/sangue , Extremidade Inferior/fisiologia , Consumo de Oxigênio/fisiologiaRESUMO
The purpose of this study was to analyse the effect of swimmer specialty on energy cost and motor organization. The stroking parameters (velocity, stroke rate, stroke length, stroke index) and the index of coordination (IdC) of 6 elite sprinters were compared with those of 6 elite long-distance swimmers during an incremental swimming exercise test (6x300 m separated by 30 s of passive recovery) that progressively increased the energy cost. Energy cost ( C), with its aerobic ( Caero) and anaerobic ( Canaero) components, was determined by measuring oxygen uptake (VO2) and blood lactate ([La]). Motor organization was assessed by analysis of video recordings from aerial and underwater side-view cameras. The results showed that throughout the test, both groups increased C, Canaero, stroke rate and IdC and decreased Caero and stroke length (all P<0.05). On the mean of the 300-m sets, sprinters had higher values for C (14.8 VS. 12.9 J x kg (-1).m (-1)), Canaero (33.8 VS. 23.4%), [La] (5.9 VS. 3.1 mmol x L (-1)), stroke length (2.31 VS. 2.28 m) and IdC (-11.2 VS. -21.7%) and lower values for Caero (66.2 VS. 79.6%), VO2 net (2 825 VS. 2 903 mL x min (-1)), stroke rate (0.55 VS. 0.62 Hz) and stroke index (2.96 VS. 3.19 m (2) x s (-1)) than long-distance swimmers (all P<0.05). For the same relative intensity, sprinters accumulated more lactate and swam more slowly than long-distance swimmers; they showed greater change in their arm coordination but their swimming economy was lower.
Assuntos
Desempenho Atlético/fisiologia , Natação/fisiologia , Adolescente , Adulto , Braço/fisiologia , Atletas , Fenômenos Biomecânicos , Metabolismo Energético/fisiologia , Humanos , Ácido Láctico/sangue , Masculino , Consumo de Oxigênio/fisiologia , Gravação de Videoteipe , Adulto JovemRESUMO
The aim of this study was two-fold: i) to analyse age-related declines in swimming, cycling, and running performances for Olympic and Ironman triathlons, and ii) to compare age-related changes in these three disciplines between the Olympic and Ironman triathlons. Swimming, cycling, running and total time performances of the top 10 males between 20 and 70 years of age (in 5 years intervals) were analysed for two consecutive world championships (2006 and 2007) for Olympic and Ironman distances. There was a lesser age-related decline in cycling performance (p<0.01) compared with running and swimming after 55 years of age for Olympic distance and after 50 years of age for Ironman distance. With advancing age, the performance decline was less pronounced (p<0.01) for Olympic than for Ironman triathlon in cycling (>55 years) and running (>50 years), respectively. In contrast, an age-related decline in swimming performance seemed independent of triathlon distance. The age-related decline in triathlon performance is specific to the discipline, with cycling showing less declines in performance with age than swimming and running. The magnitude of the declines in cycling and running performance at Ironman distance is greater than at Olympic distance, suggesting that task duration exerts an important influence on the magnitude of the age-associated changes in triathlon performance.
Assuntos
Envelhecimento/fisiologia , Ciclismo/fisiologia , Tolerância ao Exercício/fisiologia , Corrida/fisiologia , Natação/fisiologia , Adolescente , Adulto , Fatores Etários , Idoso , Análise de Variância , Estudos Transversais , Humanos , Masculino , Pessoa de Meia-Idade , Análise e Desempenho de Tarefas , Fatores de Tempo , Adulto JovemRESUMO
PURPOSE: This study investigated the effects of a combined endurance and strength training on the physiological and neuromuscular parameters during a 2-h cycling test. METHODS: Fourteen triathletes were assigned to an endurance-strength training group and an endurance-only training group. They performed three experimental trials before and after training: an incremental cycling test to exhaustion, a maximal concentric lower-limbs strength measurement and a 2-h cycling exercise. Physiological parameters, free cycling chosen cadence and the EMG of Vastus Lateralis (VL) and Rectus Femoris (RF) were analysed during the 2-h cycling task before and after a strength training programme of 5 weeks (three times per week). RESULTS: The results showed that the maximum strength and the isometric maximal voluntary contraction (isoMVC) after training were significantly higher (P<0.01) and lower (P<0.01) than those before training, respectively, in endurance-strength training group and endurance-only group. The physiological variables measured during the cycling tests and the progressive increase (P<0.01) in EMGi(VL) and EMGi(RF) throughout the 2-h cycling test did not differ between the two groups before and after training, except for the variation of EMGi(VL) over the cycle time which was stabilized during the second hour of the 2-h cycling test due to training in endurance-strength training group. The decrease in free cycling chosen cadence observed in pre-training (P<0.01) was also replaced by a steady free cycling chosen cadence for the endurance-strength training group during the second hour of exercise. CONCLUSION: This study confirmed the decrease in the free cycling chosen cadence with exercise duration and demonstrated that a specific combined endurance and strength training can prevent this decrease during a 2-h constant cycling exercise.
Assuntos
Adaptação Fisiológica/fisiologia , Ciclismo/fisiologia , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Resistência Física/fisiologia , Aptidão Física/fisiologia , Treinamento Resistido/métodos , Adulto , Humanos , Masculino , Contração Muscular/fisiologia , Análise e Desempenho de TarefasRESUMO
Knee extensor muscle strength and metabolism were examined in endurance trained young versus master athletes (10 elderly: 62.5+/-4.1 yr and 10 young: 26.2+/-2.4 yr). Before and immediately after a resistance strength training (RST), subjects performed a maximal isometric voluntary contraction (MVC) and a 10-min cycling test at a same relative intensity. During MVC, evoked contractions of the knee extensors muscles were performed to assess neuromuscular properties. Metabolism was assessed using oxygen uptake kinetics model. Before the RST session master athletes showed lower knee extensors MVC values than young subjects (257 vs. 354 N p<0.05) without any difference in oxygen kinetics (respectively for elderly and young: oxygen slow component (VO2(sc)): 231 vs. 214 ml . min(-1) and time constant (tau1): 27.8 vs. 25.1 s, p>0.05). After the RST session, a similar effect of fatigue was observed on muscular properties and oxygen kinetics whatever the group (respectively for elderly and young: MVC: -13.4 vs. -15.9%; VO2(sc): +11.8 vs.+25.2% and tau1: -15.4 vs. -13.9%). Our results suggest that the ability of master athletes to perform exercise at a given intensity is maintained despite a significant loss in strength with ageing.
Assuntos
Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Consumo de Oxigênio/fisiologia , Resistência Física/fisiologia , Adulto , Fatores Etários , Idoso , Desempenho Atlético , Ciclismo/fisiologia , Dióxido de Carbono/metabolismo , Eletromiografia , Teste de Esforço , Humanos , Contração Isométrica/fisiologia , Articulação do Joelho/fisiologia , Masculino , Pessoa de Meia-Idade , Treinamento ResistidoRESUMO
The purpose of this study was to evaluate the accuracy and the repeatability of a new running computer system (RS800sd, Polar, Kempele, Finland) which included the measurement of running speed (RS) and stride rate (SR). Eight well-trained triathletes participated in this study. First, they completed an incremental continuous maximum test on a treadmill (from 12 km x h (-1) to 18 km x h (-1)) at 0% grade. Then the subjects took part in a second test to determine RS800sd intra-reproducibility to evaluate running speed. They ran twice during 5 min at a pace corresponding to their maximal lactate steady-state. During these two tests, RS and SR were recorded by the RS800sd system, by an optical sensor system (for RS) and a force-sensitive device (for SR). No difference was found between the RS800sd system and the reference systems both for RS (ICC=0.95) and SR (ICC=0.69). Moreover RS measures were statistically repeatable. This study provided evidence for the validity of the RS800sd system for measuring the kinematic characteristics of running (speed and frequency). Further investigations are needed to replicate these findings at lower running speeds, notably during walking to assess its capacity to evaluate physical activity in natural conditions.
Assuntos
Computadores , Teste de Esforço/métodos , Corrida/fisiologia , Adulto , Fenômenos Biomecânicos , Humanos , Reprodutibilidade dos TestesRESUMO
The aim of this study was to assess stroke rate variability in elite female swimmers (200-m events, all four techniques) by comparing the semi-finalists at the Athens 2004 Olympic Games (n = 64) and semi-finalists at the French National 2004 Championship (n = 64). Since swimming speed (V) is the product of stroke rate (SR) and stroke length (SL), these three variables and the coefficient of variation of stroke rate (CV(SR)) of the first and second 100 m were determined (V1, V2; SR1, SR2; SL1, SL2; CV(SR)1, CV(SR)2) and differences between the two parts of the events were calculated (DeltaV; DeltaSR; DeltaSL; DeltaCV(SR)). When the results for the four 200-m events were analysed together, SR1, SR2, SL1, and SL2 were higher (alpha = 0.05, P< 0.001) and DeltaV, DeltaSR, and DeltaCV(SR) were lower (P< 0.01) in the Olympic group than in the National group. The Olympic-standard swimmers exhibited faster backstrokes and longer freestyle strokes (P < 0.05). Both CV(SR)1 and CV(SR)2 were lower for freestyle and backstroke races in the Olympic group than in the National group (P < 0.001). Our results suggest that stroke rate variability is dependent on an interaction between the biomechanical requisites of the task (techniques) and the standard of the swimmer.
Assuntos
Desempenho Atlético/fisiologia , Fenômenos Biomecânicos , Natação/fisiologia , Adulto , Feminino , França , Grécia , Humanos , Dinâmica não Linear , Projetos Piloto , Gravação em VídeoRESUMO
The aim of this study was to determine whether or not variable power cycling produced greater neuromuscular fatigue of knee extensor muscles than constant power cycling at the same mean power output. Eight male triathletes (age: 33+/-5 years, mass: 74+/-4 kg, VO2max: 62+/-5 mL kg(-1) min(-1), maximal aerobic power: 392+/-17 W) performed two 30 min trials on a cycle ergometer in a random order. Cycling exercise was performed either at a constant power output (CP) corresponding to 75% of the maximal aerobic power (MAP) or a variable power output (VP) with alternating +/-15%, +/-5%, and +/-10% of 75% MAP approximately every 5 min. Maximal voluntary contraction (MVC) torque, maximal voluntary activation level and excitation-contraction coupling process of knee extensor muscles were evaluated before and immediately after the exercise using the technique of electrically evoked contractions (single and paired stimulations). Oxygen uptake, ventilation and heart rate were also measured at regular intervals during the exercise. Averaged metabolic variables were not significantly different between the two conditions. Similarly, reductions in MVC torque (approximately -11%, P<0.05) after cycling were not different (P>0.05) between CP and VP trials. The magnitude of central and peripheral fatigue was also similar at the end of the two cycling exercises. It is concluded that, following 30 min of endurance cycling, semi-elite triathletes experienced no additional neuromuscular fatigue by varying power (from +/-5% to 15%) compared with a protocol that involved a constant power.
Assuntos
Ciclismo/fisiologia , Contração Muscular/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Resistência Física/fisiologia , Adulto , Análise de Variância , Estimulação Elétrica , Eletromiografia , Humanos , Articulação do Joelho/fisiologia , Masculino , Músculo Esquelético/inervação , TorqueRESUMO
The aim of this study was to investigate the effect of concentric or eccentric fatiguing exercise on cycling pattern. Eleven well trained cyclists completed three sessions of cycling (control cycling test [CTRL], cycling following concentric [CC] or eccentric [ECC] knee contractions) at a mean power of 276.8 +/- 26.6 Watts. Concentric and eccentric knee contractions were performed at a load corresponding to 80 % of one repetition maximum with both legs. Before and after CTRL, CC or ECC knee contractions and after cycling, a maximal voluntary contraction (MVC) test was performed. Cardiorespiratory, mechanical and electromyographic activity (EMG) of the rectus femoris, vastus lateralis and biceps femoris muscles were recorded during cycling. A significant decrease in MVC values was observed after CC and ECC exercises and after the cycling. ECC exercise induced a significant decrease in EMG root mean square during MVC and a decrease in pedal rate during cycling. EMG values of the three muscles were significantly higher during cycling exercise following CC exercise when compared to CTRL. The main finding of this study was that a prior ECC exercise induces a greater neuromuscular fatigue than a CC exercise, and changes in cycling pattern.
Assuntos
Ciclismo/fisiologia , Perna (Membro)/fisiologia , Fadiga Muscular/fisiologia , Adulto , Eletromiografia , Humanos , Masculino , Contração Muscular/fisiologia , Consumo de Oxigênio/fisiologia , TorqueRESUMO
The purpose of this study was to examine the relationship between strength capacity and preferred and optimal cadence in well trained cyclists. Eighteen cyclists participated in this study. Each subject completed three sessions. The initial session was to evaluate the maximal isokinetic voluntary contraction level of lower limb. The second session was an incremental test to exhaustion. During the third session subjects performed a constant cycling exercise (20 min) conducted at five randomly cadences (50, 70, 90, 110 rpm) and at the preferred cadence (FCC) at the power reached at ventilatory threshold. Cardiorespiratory and EMG values were recorded. A metabolic optimum (EOC) was observed at 63.5 +/- 7.8 rpm different from preferred cadence (FCC, 90.6 +/- 9.1 rpm). No difference was found between FCC and the neuromuscular optimal cadence (NOC, 93.5 +/- 4). Significant relationships were found between EOC, NOC and strength capacities (r = - 0.75 and - 0. 63), whereas FCC was only related with VO2max (r = 0.59). The main finding of this study was that during submaximal cycling energetically optimal cadence or neuromuscular optimum in trained cyclists was significantly related with strength capacity and whereas preferred cadence seems to be related with endurance training status of cyclists.
Assuntos
Ciclismo/fisiologia , Força Muscular/fisiologia , Resistência Física/fisiologia , Adulto , França , Humanos , Perna (Membro)/fisiologia , MasculinoRESUMO
OBJECTIVES: To determine whether the integrated electromyographic signal of two lower limb muscles indicates preferred cadence during a two hour cycling task. METHODS: Eight male triathletes performed right isometric maximum voluntary contraction (MVC) knee extension and plantar flexion before (P1) and after (P2) a two hour laboratory cycle at 65% of maximal aerobic power. Freely chosen cadence (FCC) was also determined, also at 65% of maximal aerobic power, from five randomised three minute sessions at 50, 65, 80, 95, and 110 rpm. The integrated electromyographic signal of the vastus lateralis and gastrocnemius lateralis muscles was recorded during MVC and the cycle task. RESULTS: The FCC decreased significantly (p<0.01) from P1 (87.4 rpm) to P2 (68.6 rpm), towards the energetically optimal cadence. The latter did not vary significantly during the cycle task. MVC of the vastus lateralis and gastrocnemius lateralis decreased significantly (p<0.01) between P1 and P2 (by 13.5% and 9.6% respectively). The results indicate that muscle activation at constant power was not minimised at specific cadences. Only the gastrocnemius lateralis muscle was affected by a two hour cycling task (especially at 95 and 110 rpm), whereas vastus lateralis remained stable. CONCLUSION: The decrease in FCC observed at the end of the cycle task may be due to changes in the muscle fibre recruitment pattern with increasing exercise duration and cadence.
Assuntos
Ciclismo/fisiologia , Resistência Física/fisiologia , Adulto , Eletromiografia/métodos , Metabolismo Energético/fisiologia , Teste de Esforço/métodos , Frequência Cardíaca/fisiologia , Humanos , Contração Isométrica/fisiologia , Masculino , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Consumo de Oxigênio/fisiologiaRESUMO
OBJECTIVES: To investigate the effect of cadence selection during the final minutes of cycling on metabolic responses, stride pattern, and subsequent running time to fatigue. METHODS: Eight triathletes performed, in a laboratory setting, two incremental tests (running and cycling) to determine peak oxygen uptake (VO2PEAK) and the lactate threshold (LT), and three cycle-run combinations. During the cycle-run sessions, subjects completed a 30 minute cycling bout (90% of LT) at (a) the freely chosen cadence (FCC, 94 (5) rpm), (b) the FCC during the first 20 minutes and FCC-20% during the last 10 minutes (FCC-20%, 74 (3) rpm), or (c) the FCC during the first 20 minutes and FCC+20% during the last 10 minutes (FCC+20%, 109 (5) rpm). After each cycling bout, running time to fatigue (Tmax) was determined at 85% of maximal velocity. RESULTS: A significant increase in Tmax was found after FCC-20% (894 (199) seconds) compared with FCC and FCC+20% (651 (212) and 624 (214) seconds respectively). VO2, ventilation, heart rate, and blood lactate concentrations were significantly reduced after 30 minutes of cycling at FCC-20% compared with FCC+20%. A significant increase in VO2 was reported between the 3rd and 10th minute of all Tmax sessions, without any significant differences between sessions. Stride pattern and metabolic variables were not significantly different between Tmax sessions. CONCLUSIONS: The increase in Tmax after FCC-20% may be associated with the lower metabolic load during the final minutes of cycling compared with the other sessions. However, the lack of significant differences in metabolic responses and stride pattern between the run sessions suggests that other mechanisms, such as changes in muscular activity, probably contribute to the effects of cadence variation on Tmax