摘要:

A strong relationship between aerobic fitness and the aerobic response to repeated bouts of high intensity exercise has been established, suggesting that aerobic fitness is important in determining the magnitude of the oxidative response. The elevation of exercise oxygen consumption (V-dot2) is at least partially responsible for the larger fast component of excess post-exercise oxygen consumption (EPOC) seen in endurance-trained athletes following intense intermittent exercise.Replenishment of phosphocreatine (PCr) has been linked to both fast EPOC and power recovery in repeated efforts. Although31P magnetic resonance spectroscopy studies appear to support a relationship between endurance training and PCr recovery following both submaximal work and repeated bouts of moderate intensity exercise, PCr resynthesis following single bouts of high intensity effort does not always correlate well with maximal oxygen consumption (V-dot2max). It appears that intense exercise involving larger muscle mass displays a stronger relationship between V-dot2maxand PCr resynthesis than does intense exercise utilising small muscle mass.A strong relationship between power recovery and endurance fitness, as measured by the percentage V-dot2maxcorresponding to a blood lactate concentration of 4 mmol/L, has been demonstrated. The results from most studies examining power recovery and V-dot2maxseem to suggest that endurance training and/or a higher V-dot2maxresults in superior power recovery across repeated bouts of high intensity intermittent exercise.Some studies have supported an association between aerobic fitness and lactate removal following high intensity exercise, whereas others have failed to confirm an association. Unfortunately, all studies have relied on measurements of blood lactate to reflect muscle lactate clearance, and different mathematical methods have been used for assessing blood lactate clearance, which may compromise conclusions on lactate removal.In summary, the literature suggests that aerobic fitness enhances recovery from high intensity intermittent exercise through increased aerobic response, improved lactate removal and enhanced PCr regeneration.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS

摘要:

This article traces the history of scientific and empirical interval training. Scientific research has shed some light on the choice of intensity, work duration and rest periods in so-called ‘interval training’. Interval training involves repeated short to long bouts of rather high intensity exercise (equal or superior to maximal lactate steady-state velocity) interspersed with recovery periods (light exercise or rest). Interval training was first described by Reindell and Roskamm and was popularised in the 1950s by the Olympic champion, Emil Zatopek.Since then middle- and long- distance runners have used this technique to train at velocities close to their own specific competition velocity. In fact, trainers have used specific velocities from 800 to 5000m to calibrate interval training without taking into account physiological markers. However, outside of the competition season it seems better to refer to the velocities associated with particular physiological responses in the range from maximal lactate steady state to the absolute maximal velocity. The range of velocities used in a race must be taken into consideration, since even world records are not run at a constant pace.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS

摘要:

The increased number of people taking part in deep water running (DWR) is attributable to the weight-independent characteristic of this form of exercise. Deep water runners should, however, be aware of the respiratory and cardiovascular repercussions that result from exercising in water. It has been well documented that water immersion (WI) alone results in decrements in respiratory and cardiovascular parameters in young individuals immersed in water to the neck. These decrements become more pronounced with exercise, such that maximal oxygen consumption and heart rate (HR) are lower during DWR compared with running on land. Age also seems to influence these parameters; Derion et al. found little to no change in cardiac output, stroke volume and HR during WI in older individuals compared with the decrease experienced in younger individuals. In contrast, gender appears to have no effect on WI or DWR response.Although differences in acute metabolic responses have been observed in numerous studies, training studies examining the effectiveness of using a DWR training programme found that DWR produced equivocal training responses when compared with fit and highly trained individuals running on land. Less convincing evidence has been provided for untrained individuals seeking benefits from a DWR training programme, as some studies showed significant improvements while others did not. There is a current lack of knowledge regarding the use of this form of exercise by frail elderly individuals and/or those with osteoporosis.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS

摘要:

Much of the research that has examined the interaction between metabolism and exercise has been conducted in comfortable ambient conditions. It is clear, however, that environmental temperature, particularly extreme heat, is a major practical issue one must consider when examining muscle energy metabolism. When exercise is conducted in very high ambient temperatures, the gradient for heat dissipation is significantly reduced which results in changes to thermoregulatory mechanisms designed to promote body heat loss. This can ultimately impact upon hormonal and metabolic responses to exercise which act to alter substrate utilisation. In general, the literature examining metabolic responses to exercise and heat stress has demonstrated a shift towards increased carbohydrate use and decreased fat use. Although glucose production appears to be augmented during exercise in the heat, glucose disposal and utilisation appears to be unaltered. In contrast, glycogen use has been consistently demonstrated to be augmented during exercise in the heat. This increase in glycogenolysis is observed via both aerobic and anaerobic pathways. Although several hypotheses have been proposed as mechanisms for the substrate shift towards greater carbohydrate metabolism during exercise and heat stress, recent work suggests that an augmented sympatho-adrenal response and intramuscular temperature may be responsible for such a phenomenon.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS

摘要:

The popularity of fast pitch softball in the US and throughout the world is well documented. Along with this popularity, there has been a concomitant increase in the number of injuries. Nearly 52% of cases qualify as major disabling injuries requiring 3 weeks or more of treatment and 2% require surgery. Interestingly, 75% of injuries occur during away games and ≈31% of traumas occur during nonpositional and conditioning drills. Injuries range from contusions and tendinitis to ligamentous disorders and fractures. Although head and neck traumas account for 4 to 12% of cases, upper extremity traumas account for 23 to 47% of all injuries and up to 19% of cases involve the knee.Approximately 34 to 42% of injuries occur when the athlete collides with another individual or object. Other factors involved include the quality of playing surface, athlete's age and experience level, and the excessive physical demands associated with the sport. Nearly 24% of injuries involve base running and are due to poor judgement, sliding technique, current stationary base design, unorthodox joint and extremity position during ground impact and catching of cleats. The increasing prevalence of overtraining syndrome among athletes has been attributed to an unclear definition of an optimal training zone, poor communication between player and coach, and the limited ability of bone and connective tissue to quickly respond to match the demands of the sport. This has led routinely to arm, shoulder and lumbar instability, chronic nonsteroidal anti-inflammatory drug (NSAID) use and time loss injuries in 45% of pitching staff during a single season.Specific attention to a safer playing environment, coaching and player education, and sport-specific training and conditioning would reduce the risk, rate and severity of fast pitch traumas. Padding of walls, backstops, rails and dugout areas, as well as minimising use of indoor facilities, is suggested to decrease the number of collision injuries. Coaches should be cognisant of overtraining, vary day-to-day training routines to decrease repetitive musculoskeletal stress, focus on motor skills with equal emphasis on speed and efficiency of movement, and use drills that reinforce sport-specific, decision making processes to minimise mental mistakes. Conditioning programs that emphasise a combination of power, acceleration, flexibility, technical skill, functional capacity and injury prevention are recommended. Due to the limited body of knowledge presently available on this sport, a greater focus on injury surveillance would provide a clearer picture of injury causation and effective management procedures, leading toward safer participation and successful player development.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS