RESUMEN
OBJECTIVES: The aim was to determine whether daily muscle electrical stimulation (ES) and streptomycin treatment would have positive or negative effects on trabecular bone mass in disuse rats. METHODS: Seven-week-old male F344 rats were randomly divided into five groups of eight animals each: an age-matched control group (CON); a sciatic denervation group (DN); a DN + direct electrical stimulation group (DN+ES); a DN + streptomycin treatment group (DN+SM); and a DN+ES+SM group. The tibialis anterior (TA) muscles in all ES groups were stimulated with 16mA at 10Hz for 30 min/day, six days/week, for one week. Bone volume and structure were evaluated using micro-CT, and histological examinations of the tibiae were performed. RESULTS: Direct ES significantly reduced the disuse-induced trabecular bone loss. Osteoid thickness were also significantly greater in the ES groups than in the DN group. Micro CT and histomorphological parameters were significantly lower in the DN+ES+SM group than in the DN+ES group, while there were no significant differences between the DN and DN+SM groups. CONCLUSIONS: These results suggest that ES-induced muscle force reduced trabecular bone loss, and streptomycin treatment did not induce bone loss, but attenuated the effects of ES-induced muscle force on reducing the loss of disused bone.
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Huesos/efectos de los fármacos , Estimulación Eléctrica/métodos , Trastornos Musculares Atróficos/patología , Inhibidores de la Síntesis de la Proteína/farmacología , Estreptomicina/farmacología , Animales , Huesos/diagnóstico por imagen , Desnervación , Modelos Animales de Enfermedad , Electromiografía , Masculino , Trastornos Musculares Atróficos/diagnóstico por imagen , Ratas , Ratas Endogámicas F344 , Microtomografía por Rayos XRESUMEN
OBJECTIVES: We aimed to determine the intensity of muscle stimulation required to prevent structural failure as well as bone and skeletal muscle loss after denervation-induced disuse. METHODS: Seven-week-old rats (weight, 198-225 g) were randomly assigned to age-matched groups comprising control (CON), sciatic nerve denervation (DN) or direct electrical stimulation (ES) one day later [after denervation] with 4, 8 and 16 mA at 10 Hz for 30 min/day, six days/week, for one or three weeks. Bone architecture and mean osteoid thickness in histologically stained tibial sections and tension in tibialis anterior muscles were assessed at one and three weeks after denervation. RESULTS: Direct ES with 16 mA generated 23-30% maximal contraction force. Denervation significantly decreased trabecular bone volume fraction, thickness and number, connectivity density and increased trabecular separation in the DN group at weeks one and three. Osteoid thickness was significantly greater in the ES16 group at week one than in the DN and other ES groups. Trabecular bone volume significantly correlated with muscle weight. CONCLUSIONS: Relatively low-level muscle contraction induced by low-frequency, high-intensity electrical muscle stimulation delayed trabecular bone loss during the early stages (one week after DN) of musculoskeletal atrophy due to disuse.
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Resorción Ósea/prevención & control , Músculo Esquelético/fisiología , Trastornos Musculares Atróficos/fisiopatología , Tibia/fisiopatología , Animales , Desnervación , Modelos Animales de Enfermedad , Terapia por Estimulación Eléctrica , Masculino , Ratas , Ratas Wistar , Microtomografía por Rayos XRESUMEN
The present study aimed to determine the intra-abdominal pressure during front crawl swimming at different velocities in competitive swimmers and to clarify the relationships between stroke indices and changes in intra-abdominal pressure. The subjects were 7 highly trained competitive collegiate male swimmers. Intra-abdominal pressure was measured during front crawl swimming at 1.0, 1.2 and 1.4 m · s(-1) and during the Valsalva maneuver. Intra-abdominal pressure was taken as the difference between minimum and maximum values, and the mean of 6 stable front crawl stroke cycles was used. Stroke rate and stroke length were also measured as stroke indices. There were significant differences in stroke rate among all velocities (P < 0.05). However, there was no significant difference in stroke length by velocity. Significant within-subject correlations between intra-abdominal pressure and stroke rate or stroke length (P < 0.01) were observed, although there were no significant correlations between intra-abdominal pressure and stroke indices when controlling for swimming velocity. These findings do not appear to support the effectiveness of trunk training performed by competitive swimmers aimed at increasing intra-abdominal pressure.
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Abdomen/fisiología , Presión , Natación/fisiología , Adolescente , Humanos , Recto/fisiología , Maniobra de Valsalva , Adulto JovenRESUMEN
OBJECTIVE: The present study aimed to clarify the structural recovery, and to compare the time course of morphological changes in trabeculae and the process of bone mass change in rat tibiae following temporary immobilization of hind limb by sciatic neurectomy or nerve freezing. METHODS: In 11-week-old male Fischer 344 rats, 4-5 mm of the sciatic nerve was removed (neurectomy group) or frozen by 5-second application of a stainless steel rod immersed in liquid nitrogen (nerve-freezing group). Quantitative changes in cancellous bone were assessed by histomorphometry. RESULTS: The results clarified that: trabecular bone volume (BV/TV) decreases until 3 weeks after denervation, and in the nerve-freezing group, it then increases from week 4, recovering to pre-surgery levels by week 10 (no recovery was seen in the neurectomy group); in the initial phase of bone atrophy, the decrease in BV/TV is more gradual in the nerve-freezing group than in the neurectomy group; and changes in trabecular architecture in the bone atrophy-recovery process are strongly associated with changes in trabecular thickness. CONCLUSION: The findings suggested that after transient injury by nerve freezing and subsequent recovery of neuromuscular function, bone tissue undergoes recovery from bone loss, but that trabeculae may not show complete structural recovery.
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Remodelación Ósea/fisiología , Tibia/patología , Animales , Atrofia/etiología , Atrofia/patología , Desnervación , Modelos Animales de Enfermedad , Masculino , Ratas , Ratas Endogámicas F344 , Nervio Ciático/cirugía , Tibia/inervación , TiempoRESUMEN
Previous studies reported that aerobic-type exercise such as walking or cycling with blood flow restriction (BFR) has been shown to elicit increases in leg muscle hypertrophy and strength, as well as improved aerobic capacity. Although previous studies investigated cardiovascular responses during a relatively short duration of exercise (â¼5 min), the effects of prolonged leg muscular BFR have remained unknown. The purpose of this study was to examine the cardiovascular effects of longer duration low intensity exercise combined with BFR. Eight men performed 30 min of exercise at 40% of a predetermined maximal oxygen uptake under both BFR and normal flow (CON) conditions. Cardiovascular parameters were measured at rest and every 10 min during exercise. The main findings were that 1) the SV and HR did not change significantly between 10 to 30 min of exercise in BFR and CON conditions, although BFR-induced reduction of SV and increased HR were found at 10 min exercise compared with normal flow, 2) blood pressure was increased at 10 min of exercise in BFR compared to the CON, however the blood pressure decreased gradually with BFR from 10 to 30 min of exercise, and 3) blood lactate and RPE increased gradually during exercise with BFR. In conclusion, our results suggest that the BFR-induced reduction of SV and increased HR within the first 10 min of exercise are representative of changes in these parameters.
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Ejercicio Físico/fisiología , Pierna/irrigación sanguínea , Flujo Sanguíneo Regional/fisiología , Entrenamiento de Fuerza/métodos , Resistencia Vascular/fisiología , Adulto , Presión Sanguínea/fisiología , Gasto Cardíaco/fisiología , Ecocardiografía Doppler , Prueba de Esfuerzo , Tolerancia al Ejercicio/fisiología , Frecuencia Cardíaca/fisiología , Hemodinámica/fisiología , Humanos , Ácido Láctico/sangre , Pierna/diagnóstico por imagen , Masculino , Consumo de Oxígeno/fisiología , Adulto JovenRESUMEN
In the present study, we aimed to determine whether response training shortens visuo-motor related time in athletes performing a simple reaction task. 14 healthy male athletes were included in the study. Subjects were randomly divided into 2 groups: a training group, which underwent response training consisting of a mastication task in response to a visual signal, and a non-training (control) group, which did not undergo response training. Pre-motor time and transcranial magnetic stimulation over the primary motor cortex for recording motor evoked potentials were measured in the control group, and before and after the response training session in the training group. Both pre-motor time and visuo-motor related time, but not motor evoked potential latency, were significantly reduced after response training in the training group. Subjects who had a longer visuo-motor related time before training showed a greater reduction in visuo-motor related time after training. These results suggest that visuo-motor related time before training could be useful as a predictor of the reduction in reaction time following response training.
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Atletas , Desempeño Psicomotor/fisiología , Tiempo de Reacción , Adolescente , Potenciales Evocados Motores , Humanos , Masculino , Masticación , Factores de Tiempo , Estimulación Magnética Transcraneal , Adulto JovenRESUMEN
We investigated the expression of vascular endothelial growth factor (VEGF) and its receptors (Flt-1 and KDR/Flk-1) during muscle regeneration by immunohistochemistry and real-time RT-PCR. On days 5 and 7 after the induction of injury, VEGF and Flt-1 were detected in the cytoplasm and KDR/Flk-1 in the cytoplasm and on cell membranes of the same regenerating muscle fibers. The levels of these proteins in the regenerating muscle fibers gradually decreased until day 20. In contrast, these proteins were not detected in the fibers of normal muscle. This suggests that regenerating muscle fibers express VEGF and its receptors in response to injury. In addition, we found that the VEGF mRNA transcript transiently increased after 12 h of muscle injury and then returned to the basal levels observed in normal muscles on day 1. The expression of Flt-1 and KDR/Flk-1 mRNA transcripts also peaked on day 3 and then returned to the basal levels observed in normal muscles on day 10. These findings suggest that regenerating muscle fibers are an important source of VEGF and that VEGF signaling through Flt-1 and KDR/Flk-1 may be involved in the process of muscle regeneration in vivo.
Asunto(s)
Músculo Esquelético/metabolismo , Regeneración , Factor A de Crecimiento Endotelial Vascular/metabolismo , Receptor 1 de Factores de Crecimiento Endotelial Vascular/metabolismo , Receptor 2 de Factores de Crecimiento Endotelial Vascular/metabolismo , Animales , Peso Corporal , Membrana Celular/metabolismo , Citoplasma/metabolismo , Congelación , Inmunohistoquímica , Masculino , Ratones , Músculo Esquelético/patología , Músculo Esquelético/fisiopatología , Músculo Esquelético/cirugía , Tamaño de los Órganos , ARN Mensajero/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal , Factores de TiempoRESUMEN
Capillary supply of skeletal muscle decreases during denervation. To gain insight into the regulation of this process, we investigated capillary supply and gene expression of angiogenesis-related factors in mouse gastrocnemius muscle following denervation for 4 months. Frozen transverse sections were stained for alkaline phosphatase to detect endogenous enzyme in the capillary endothelium. The mRNA for angiogenesis-related factors, including hypoxia inducible factor-1alpha (HIF-1alpha), vascular endothelial growth factor (VEGF), kinase insert domain-containing receptor/fetal liver kinase-1 (KDR/Flk-1), fms-like tyrosine kinase (Flt-1), angiopoietin-1 and tyrosine kinase with Ig and epidermal growth factor(EGF) homology domain 2 (Tie-2), was analysed using a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). The fibre cross-sectional area after denervation was about 20% of the control value, and the capillary to fibre ratio was significantly lower in denervated than in control muscles. The number of capillaries around each fibre also decreased to about 40% of the control value. These observations suggest that muscle capillarity decreases in response to chronic denervation. RT-PCR analysis showed that the expression of VEGF mRNA was lower in denervated than in control muscles, while the expression of HIF-1alpha mRNA remained unchanged. The expression levels of the KDR/Flk-1 and Flt-1 genes were decreased in the denervated muscle. The expression levels of angiopoietin-1 but not Tie-2 genes were decreased in the denervated muscle. These findings indicate that reduction in the expression of mRNAs in the VEGF/KDR/Flk-1 and Flt-1 as well as angiopoietin-1/Tie-2 signal pathways might be one of the reasons for the capillary regression during chronic denervation.
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Proteínas Angiogénicas/metabolismo , Capilares/citología , Desnervación Muscular/métodos , Proteínas Musculares/metabolismo , Músculo Esquelético/irrigación sanguínea , Músculo Esquelético/inervación , Neovascularización Fisiológica/fisiología , Animales , Regulación de la Expresión Génica/fisiología , Masculino , Ratones , Ratones Endogámicos ICR , Músculo Esquelético/citología , Músculo Esquelético/metabolismoRESUMEN
PURPOSE: The purpose of this study was to determine the primary factors causing the differential oxygen uptake (VO2) response at submaximal intensities between one-legged and two-legged exercise, and whether peak oxygen uptake (VO2peak) increases in proportion to the increase in active muscle mass. METHODS: Two different types of exercise were used for this experiment, each requiring a different movement, a different method of stabilizing posture, and, finally, a different limiting VO2peak. In experiment 1, nine male subjects performed one-legged cycling (OLC) and two-legged cycling exercise (TLC) at a pedaling rate of 80 rpm. The exercise intensity was first set at 80 W and was increased by 40 W every 3 min until exhaustion. In experiment 2, six healthy male subjects performed one-legged knee-extension (OKE) and two-legged knee-extension (TKE) exercise at a rate of 50 contractions per minute. The knee-extension exercise was done at constant work rates for a 3-min session in OKE or a 4-min session in TKE. The exercise bouts were performed intermittently at four to seven different submaximal intensities and VO2 was determined at each intensity in all exercises. RESULTS: At submaximal intensities, VO2 in relation to work rate of one-legged exercise was more steep than those of two-legged exercise, and the mean values of VO2 were significantly higher in one-legged exercise than those in two-legged exercise in both knee extension and cycling exercise. Mean values of VO2peak for two-legged exercise were significantly higher than that for one-legged exercise (P < 0.01); however, it was much lower than two times of that for one-legged exercise even in knee extension exercise where the VO2peak would be limited peripherally. CONCLUSION: The findings of this study suggest that the differential VO2 response between one-legged and two-legged exercise would be attributed not only to the difference in force application throughout the exercise movement and to the effect of a postural component but also to the inhibited circulatory response caused by the multiple limb exercise. In addition, it was supposed that VO2peak does not increase in proportion to the exercising muscle mass even during smaller muscle activity where the cardiac pumping capacity has not reached its upper limit.
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Prueba de Esfuerzo , Tolerancia al Ejercicio/fisiología , Consumo de Oxígeno , Oxígeno/sangre , Adulto , Humanos , Pierna , Modelos Lineales , MasculinoRESUMEN
PURPOSE: Swimmers swim faster using hand paddles. In this study the effect of maximal performance using hand paddles on aerobic and anaerobic energy release during supramaximal swimming was examined by comparing the maximal accumulated O2 deficit, and the aerobic and anaerobic energy release during exhaustive swimming with paddles (P) to swimming without paddles (hands only, H). METHODS: The subjects were six trained college male swimmers. Experiments were carried out in a swimming flume. The water flow rate was set before each exercise bout such that exhaustion occurred in 30 s, 1 min, or 2-3 min. Accumulated O2 deficit during exercise was determined by the accumulated oxygen demand minus the accumulated O2 uptake. RESULTS: Water flow rates at which maximal accumulated O2 deficit was obtained were significantly higher in P than that in H. However, mean values of maximal accumulated O2 deficit during H and P were 2.40+/-0.42 L and 2.32+/-0.37 L, respectively, and there was no significant difference between these two values. Furthermore, during the supramaximal swimming to exhaustion in 30 s, 1 min, or 2-3 min, both accumulated O2 uptake and accumulated O2 deficit did not significantly differ between these conditions, although mean water flow rates of these supramaximal swimming bouts were significantly higher in P than those in H again. CONCLUSIONS: These results suggest that the faster swimming speed accomplished with hand paddles does not affect metabolic responses and that it may be realized by recruitment of roughly the same muscle mass. Therefore, the ability to swim faster with hand paddles might mainly be attributed to other than metabolic factors, i.e., a higher propelling efficiency.
Asunto(s)
Metabolismo Energético/fisiología , Natación/fisiología , Adulto , Anaerobiosis/fisiología , Ejercicio Físico/fisiología , Humanos , Masculino , Mecánica RespiratoriaRESUMEN
PURPOSE: Competitive pool swimming events range in distance from 50 to 1500 m. Given the difference in performance times (+/- 23-1000 s), the contribution of the aerobic and anaerobic energy systems changes considerably with race distance. In training practice the regression line between swimming distance and time (Distance = critical velocity x time + anaerobic swimming capacity) is used to determine the individual capacity of the aerobic and anaerobic metabolic pathways. Although there is confidence that critical velocity and anaerobic swimming capacity are fitness measures that separate aerobic and anaerobic components, a firm theoretical basis for the interpretation of these results does not exist. The purpose of this study was to evaluate the critical power concept and anaerobic swimming capacity as measures of the aerobic and anaerobic capacity using a modeling approach. METHODS: A systems model was developed that relates the mechanics and energetics involved in front crawl swimming performance. From actual swimming flume measurements, the time dependent aerobic and anaerobic energy release was modeled. Data derived from the literature were used to relate the energy cost of front crawl swimming to swimming velocity. A balance should exist between the energy cost to swim a distance in a certain time and the concomitant aerobic and anaerobic energy release. The ensuing model was used to predict performance times over a range of distances (50-1500 m) and to calculate the regression line between swimming distance and time. RESULTS AND CONCLUSIONS: Using a sensitivity analysis, it was demonstrated that the critical velocity is indicative for the capacity of the aerobic energy system. Estimates of the anaerobic swimming capacity, however, were influenced by variations in both anaerobic and aerobic energy release. Therefore, it was concluded that the anaerobic swimming capacity does not provide a reliable estimate of the anaerobic capacity.
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Umbral Anaerobio , Metabolismo Energético/fisiología , Resistencia Física/fisiología , Natación/fisiología , Adolescente , Adulto , Fenómenos Biomecánicos , Humanos , Masculino , Modelos Teóricos , Factores de TiempoRESUMEN
To evaluate the magnitude of the stress on the aerobic and the anaerobic energy release systems during high intensity bicycle training, two commonly used protocols (IE1 and IE2) were examined during bicycling. IE1 consisted of one set of 6-7 bouts of 20-s exercise at an intensity of approximately 170% of the subject's maximal oxygen uptake (VO2max) with a 10-s rest between each bout. IE2 involved one set of 4-5 bouts of 30-s exercise at an intensity of approximately 200% of the subject's VO2max and a 2-min rest between each bout. The accumulated oxygen deficit of IE1 (69 +/- 8 ml.kg-1, mean +/- SD) was significantly higher than that of IE2 (46 +/- 12 ml.kg-1, N = 9, p < 0.01). The accumulated oxygen deficit of IE1 was not significantly different from the maximal accumulated oxygen deficit (the anaerobic capacity) of the subjects (69 +/- 10 ml.kg-1), whereas the corresponding value for IE2 was less than the subjects' maximal accumulated oxygen deficit (P < 0.01). The peak oxygen uptake during the last 10 s of the IE1 (55 +/- 6 ml.kg-1.min-1) was not significantly less than the VO2max of the subjects (57 +/- 6 ml.kg-1.min-1). The peak oxygen uptake during the last 10 s of IE2 (47 +/- 8 ml.kg-1.min-1) was lower than the VO2max (P < 0.01). In conclusion, this study showed that intermittent exercise defined by the IE1 protocol may tax both the anaerobic and aerobic energy releasing systems almost maximally.
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Ciclismo/fisiología , Metabolismo Energético , Adulto , Umbral Anaerobio/fisiología , Análisis de Varianza , Ergometría , Tolerancia al Ejercicio , Humanos , Modelos Lineales , Masculino , Consumo de Oxígeno/fisiología , Resistencia Física , Descanso/fisiologíaRESUMEN
This study consists of two training experiments using a mechanically braked cycle ergometer. First, the effect of 6 wk of moderate-intensity endurance training (intensity: 70% of maximal oxygen uptake (VO2max), 60 min.d-1, 5 d.wk-1) on the anaerobic capacity (the maximal accumulated oxygen deficit) and VO2max was evaluated. After the training, the anaerobic capacity did not increase significantly (P > 0.10), while VO2max increased from 53 +/- 5 ml.kg-1 min-1 to 58 +/- 3 ml.kg-1.min-1 (P < 0.01) (mean +/- SD). Second, to quantify the effect of high-intensity intermittent training on energy release, seven subjects performed an intermittent training exercise 5 d.wk-1 for 6 wk. The exhaustive intermittent training consisted of seven to eight sets of 20-s exercise at an intensity of about 170% of VO2max with a 10-s rest between each bout. After the training period, VO2max increased by 7 ml.kg-1.min-1, while the anaerobic capacity increased by 28%. In conclusion, this study showed that moderate-intensity aerobic training that improves the maximal aerobic power does not change anaerobic capacity and that adequate high-intensity intermittent training may improve both anaerobic and aerobic energy supplying systems significantly, probably through imposing intensive stimuli on both systems.
Asunto(s)
Umbral Anaerobio/fisiología , Consumo de Oxígeno , Educación y Entrenamiento Físico/métodos , Resistencia Física/fisiología , Adulto , Humanos , MasculinoRESUMEN
In the present study, we determined both anaerobic capacity (the maximal accumulated oxygen deficit) and maximal oxygen uptake (VO2max) during arm stroke (A), leg kicking (K), and whole body swimming (S), and compared them. The subjects were six trained college swimmers (two male and four female), aged 20 +/- 1 years. To determine VO2max for A, K and S, VO2max was measured during a 6-min swim at constant water flow rates. VO2 was measured by the Douglas bag method. Anaerobic capacity was determined by accumulated oxygen deficit during exercise lasting 2-3 min according to the methods of Medbø et al. Mean values of VO2max during A, K and S were 2.53 +/- 0.37 L min-1, 2.93 +/- 0.37 L min-1, and 3.23 +/- 0.43 L min-1, respectively. Those in A and K corresponded to 78.2% and 91.0% of that in S. Mean values of anaerobic capacity during A, K and S were 2.15 +/- 0.31 L, 2.52 +/- 1.08 L and 2.99 +/- 0.52 L, respectively. Those in A and K corresponded to 73.3% and 81.7% of that in S. Both VO2max and anaerobic capacity in S were much lower than the sum of A and K, corresponding to only 59.3% and 65.9%, respectively. These results suggest that the total energy production during S is lower than simply the sum of A and K because the potentials of both the anaerobic and aerobic energy releasing processes in the muscle groups involved in A and K cannot be fully reached during S.
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Consumo de Oxígeno/fisiología , Natación/fisiología , Adulto , Aerobiosis/fisiología , Anaerobiosis/fisiología , Brazo , Ejercicio Físico/fisiología , Femenino , Humanos , Pierna , MasculinoRESUMEN
The present study aimed to determine whether vasoconstriction in active calf occurring during combined exercise diminished or persisted when added low- and high-intensity elbow flexion exercise ceased and single leg exercise continued. Six active women (mean age, 21.2 years) participated in this study. During 10-min plantar flexion exercise at 10% of maximum voluntary contraction (MVC), elbow flexion exercise at 10% MVC was added over the 3rd and 4th min. Calf blood flow did not change significantly upon superimposition and cessation of this elbow flexion exercise. However, when elbow flexion exercise at 50% MVC was added during the 7th and 8th min, calf blood flow above the resting value (2.23 +/- 0.23 mL 100 mL-1 min-1) decreased significantly (P < 0.05) from 6.72 +/- 0.87 (6th min) to 5.14 +/- 1.36 mL 100 mL-1 min-1 after 2 min of combined exercise and was accompanied by a similar change in the non-exercising calf blood flow value. The vascular conductance of the exercising calf decreased significantly (P < 0.01) from 6.48 +/- 1.08 (6th min) to 3.11 +/- 1.27 mL 100 mL-1 min-1 mmHg-1 at the end of the 2nd min of combined plantar flexion exercise with elbow flexion exercise at 50% MVC. After elbow flexion exercise at 50% MVC was discontinued and plantar flexion exercise at 10% MVC alone was performed, the vascular conductance in the exercising calf remained significantly low for the next 2 min. These results indicate that the vasoconstriction induced by adding high-intensity arm exercise is persistent, suggesting a major contribution of metabo-receptor-mediated vasoconstriction rather than central command- and mechano-receptor-mediated vasoconstriction.
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Articulación del Codo/fisiología , Movimiento/fisiología , Músculo Esquelético/irrigación sanguínea , Músculo Esquelético/fisiología , Vasoconstricción/fisiología , Adulto , Velocidad del Flujo Sanguíneo , Presión Sanguínea/fisiología , Femenino , Frecuencia Cardíaca/fisiología , Humanos , Pierna/irrigación sanguínea , Pierna/fisiología , Contracción Muscular/fisiología , Consumo de Oxígeno , Pletismografía , Rango del Movimiento ArticularRESUMEN
The purpose of this study was to examine whether cardiorespiratory responses to combined rhythmic exercise (60 contractions.min-1) was affected by different combinations of upper and lower limb exercise in seven healthy women. Six different rhythmic exercises were compared: 6-min rhythmic handgrip at 10% of isometric maximal voluntary contraction (MVC) (H10); 6-min rhythmic plantar flexion at 10% MVC (P10); exhausting rhythmic handgrip at 50% MVC (H50); exhausting rhythmic plantar flexion at 50% MVC (P50); H50 was added to P10 (P10H50); and P50 was added to H10 (H10P50). Exercise duration, after handgrip was combined with plantar flexion (P10H50), was shorter than that of H50, although the exercise duration of H10P50 was not significantly different from P50. No significant difference was found between the difference from rest in oxygen uptake (delta VO2) during H10P50 and the sum of delta VO2 during H10 and P50. Also, the differences from rest in forearm blood flow (delta FBF) and calf blood flow (delta CBF) during H10P50 were not significantly different from delta FBF in H10 and from delta CBF in P50. In contrast, delta VO2 in P10H50 was lower than the sum of delta VO2 in P10 and H50 (P < 0.05), and delta FBF in P10H50 was lower than that in H50 (P < 0.05), while delta CBF was not significantly different between P10H50 and P10. The changes in heart rate from rest (delta HR) during the combined exercises were lower than the sums of delta HR in the corresponding single exercises (P < 0.05). These results demonstrated an inhibitory summation of several cardiorespiratory responses to combined exercise resulting in a reduction in exercise performance which would seem to occur easily when upperlimb exercise is added to lower limb exercise.
Asunto(s)
Ejercicio Físico/fisiología , Antebrazo , Corazón/fisiología , Pierna , Respiración/fisiología , Adulto , Femenino , Antebrazo/irrigación sanguínea , Fuerza de la Mano , Frecuencia Cardíaca , Humanos , Contracción Isométrica , Pierna/irrigación sanguínea , Contracción Muscular , Consumo de OxígenoRESUMEN
To compare maximal cardio-respiratory stress between swim-bench exercise (SB) and arm stroke (AS), peak oxygen uptake (VO2peak) was measured in six trained swimmers. The SB was performed at stroke frequency of 50.min-1. Oxygen uptake (VO2) was measured during exercise at 3-min constant exercise intensities in SB and at 4-min constant water flow rates in AS. We measured a steady-state VO2 within 3 or 4 min after the beginning of each exercise. The exercise intensity or the water flow rate was increased by 14.7 W or by 0.05 m.s-1, respectively, until a levelling-off of VO2 was observed. The VO2 was measured by the Douglas bag method. Heart rate (HR) and blood lactate concentration ([la-]b) were determined at the exercise intensity and the water flow rate at which VO2peak was obtained. At submaximal levels, VO2 increased in proportion to exercise intensity for SB and to the water flow rate for AS. A levelling-off of VO2 was observed in all subjects for both kinds of exercise. The VO2peak during SB [2.13 (SD 0.25)1.min-1] was significantly lower than that during AS [2.72 (SD 0.39)1.min-1] and corresponded to 78.9 (SD 7.0)% of AS VO2peak. Maximal HR during SB was also significantly lower than that during AS. No significant differences between SB and AS were found for either pulmonary ventilation or [la-]b. The peak exercise duration in SB [2.4 (SD 0.5) min] was significantly shorter than that in As [3.6 (SD 0.5) min]. These results would suggest that even though both kinds of exercise use the muscles of the upper body, active muscle groups involved during SB are different and/or smaller, and maximal stress on the cardio-respiratory system is lower when compared to AS.
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Ejercicio Físico/fisiología , Consumo de Oxígeno/fisiología , Natación , Adulto , Brazo/fisiología , Corazón/fisiología , Frecuencia Cardíaca/fisiología , Humanos , Lactatos/sangre , Ácido Láctico , Masculino , Mecánica Respiratoria/fisiología , Relación Ventilacion-Perfusión/fisiologíaRESUMEN
The calf and forearm blood flows (Qcalf and Qforearm respectively), blood pressure, heart rate and oxygen uptake of six men and women were studied during combined leg and handgrip exercise to determine whether a reduction of exercise-induced hyperaemia would occur in the active leg when exhausting rhythmic handgrip exercise at 50% maximal voluntary contraction (MVC) was superimposed upon rhythmic plantar flexion lasting for 10 min at 10% MVC (P10) prior to this combined exercise. The Qcalf and Qforearm were measured by venous occlusion plethysmography during 5-s rests interposed during every minute of P10 exercise and immediately after combined exercise. The muscle sympathetic nerve activity (MSNA) changes were also recorded during leg exercise alone and combined exercise. During plantar flexion performed 60 times.min-1 with a load equal to 10% MVC (P10), Qcalf was maintained at a constant level, which was significantly higher than the resting value (P < 0.001). When rhythmic handgrip contraction at 50% MVC (H50) and P10 were performed simultaneously, the combined exercise was concluded due to forearm exhaustion after a mean of 51.2 (SEM 5.5) s. At exhaustion, Qcalf had decreased significantly from 20.6 (SEM 3.0) ml.100 ml-1.min-1 (10th min during P10 exercise) to 15.3 (SEM) ml.100 ml-1.min-1 (P = 0.001), whereas Qforearm had increased significantly (0.001 < P < 0.01) from 8.6 (SEM 1.9) ml.100 ml-1.min-1 (10th min of P10 exercise) to 26.2 (SEM 3.2) ml.100 ml-1.min-1. The mean blood pressure remained at an almost constant level during the 3rd to 10th min of P10 exercise and increased markedly when H50 was added.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Mano/irrigación sanguínea , Mano/fisiología , Pierna/irrigación sanguínea , Músculos/irrigación sanguínea , Resistencia Física , Esfuerzo Físico , Adulto , Femenino , Humanos , Masculino , Contracción Muscular , Músculos/inervación , Consumo de Oxígeno , Flujo Sanguíneo Regional , Sistema Nervioso Simpático/fisiologíaRESUMEN
Cardiorespiratory responses during arm-stroke-only swimming with and without the aid of paddle were compared in seven trained swimmers. Water flow rate was started at 0.80 m.s-1 and was increased by 0.05 m.s-1 every 2 min up. to 1.00 m.s-1. Subsequently, the flow rate was increased by 0.05 m.s-1 every minute until exhaustion. At given submaximal water flow rates, oxygen uptake, heart rate (fc), pulmonary ventilation (VE) and respiratory frequency (fR) during swimming using hands alone (H) were significantly higher than when aided by paddles (P). There were no significant differences in tidal volume (VT) between H and P. The subjects were able to swim significantly faster using paddles (P < 0.05); however, no significant differences between H and P were found in peak oxygen uptake (VO2peak, Fc, VE, FR, VT and the blood lactate concentration at which VO2peak was obtained (P > 0.05). These results would suggest that the ability to swim faster with paddles does not depend on higher energy production but may be attributed to higher propelling efficiency.
Asunto(s)
Consumo de Oxígeno/fisiología , Natación/fisiología , Adulto , Brazo/fisiología , Fenómenos Biomecánicos , Metabolismo Energético , Frecuencia Cardíaca , Humanos , Masculino , RespiraciónRESUMEN
In order to examine efferent sympathetic nerve control of the peripheral circulation during exercise, muscle sympathetic nerve activity (MSNA), calf blood flow (CBF), heart rate (HR), blood pressure (BP) and oxygen uptake were measured during combined foot and forearm exercise. An initial period of rhythmic foot exercise (RFE) (60 min-1 at 10% of maximal voluntary contraction (MVC) was followed by the addition of rhythmic handgrip exercise (RFE + OCCL) (60 min at 30% of MVC) and by forearm ischaemia after handgrip exercise while continuing RFE (RFE + OCCL). During RFE, CBF in the working leg, HR and oxygen increased respectively by 560%, 121% and 144% when compared with the control rest period, but MSNA (burst rate) was reduced by 13% (P > 0.05) and BP was unchanged. During RFE + RHG, HR, BP and oxygen uptake were greater than during RFE alone. There was no change in CBF, but a significant increase occurred in calf vascular resistance (CVR) and MSNA increased to 121% of the control level. During RFE + OCCL, MSNA, CVR and BP were all higher than during RFE alone, whereas HR and oxygen uptake decreased slightly, although they remained higher than the control values. The increase in CVR in the working leg and the rise in BP during RFE + RHG or RFE + OCCL might be linked to enhancement of MSNA, which may have been reflexly evoked by input from muscle metabolic receptors in the working forearm.