ISSN:0112-1642    

DOI:10.2165/00007256-199519040-00001

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

ISSN:0112-1642    

DOI:10.2165/00007256-199519040-00002

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryThe triathlon is a 3-event endurance sport in which athletes compete sequentially in swimming, cycling and running. The primary determinant of success is the ability to sustain a high rate of energy expenditure for prolonged periods of time. Exercise training-induced physiological adaptations in virtually all systems of the body allow the athlete to accomplish this. Aerobic capacity (measured as maximal oxygen uptake, V̇O2max), economy of motion (submaximal V̇O2) and fractional utilisation of maximal capacity (%V̇O2max) reflect the integrated responses of these physiological adaptations.Numerous studies have reported relatively high mean V̇O2max) values for various groups of triathletes that are comparable to those reported for athletes in single-event endurance sports and clearly above those reported for untrained individuals. In shorter distance triathlons and in studies using recreational (rather than elite) triathletes, V̇O2maxis related to performance in the corresponding event of the triathlon (e.g. tethered swimming V̇O2maxwith swim time). In longer events and with more elite triathletes, V̇O2maxCorrelates less well with performance. The physiological adaptations that correspond to and facilitate improved V̇O2maxoccur centrally in the cardiovascular system, centred on increased maximal cardiac output, and peripherally in the metabolic systems, centred around increased arterio-venous O2(a-v O2) difference.While a high V̇O2maxin individuals is clearly of importance to triathlon performance, energy output must be sustained for long periods of time, making economy of motion also very important. Studies suggests that competitive swimmers have better swimming economy than triathletes. However, since many triathletes have previously been competitive swimmers this finding is questionable. The finding suggests that triathletes from nonswimming backgrounds would benefit from improving swimming technique rather than concentrating training workouts solely on distance. In cycling and running, comparison studies have not been done. Economy of motion in swimming, cycling and running have all been found to be correlated with comparable event performance. Training to improve swimming economy can be done without prior exercise, but training to improve cycling and running economy should take the multimode nature of a triathlon into consideration. That is, swimming should precede cycling economy training, and cycling should precede running economy training. Cardiovascular, metabolic and neuromuscular adaptations are the main physiological correlates of improved movement economy.Since exercise-induced stress on most physiological systems is based on relative, rather than absolute, exercise intensity, training and racing intensities are frequently quantified as a percentage of maximal capacity or %V̇O2max. Several studies of triathletes have examined the role of %V̇O2maxin triathlon performance, and have found relatively high correlations for each of the triathlon events with event-specific fractional utilisations. The %V̇O2maxaccessible is governed by several physiological systems, but most importantly by the lactate threshold. For the triathlete, lactate thresholds during swimming, cycling and running may all occur at different energy outputs, percentages of maximal capacity and heart rates. Lactate thresholds, therefore, must be measured independently in each of the 3 sports.In addition to V̇O2maxmovement economy and fractional utilisation of maximal capacity, considerations of energy balance, fluid and electrolyte balance as well as cardiac function over time are important for the success of the triathlete. The triathlete must maintain energy stores on a day-to-day basis during training and be able to generate energy at a high rate during the race. Likewise, fluid and electrolyte balance must be maintained daily as well as during the race. Continued and appropriate cardiovascular function is necessary for the transport of nutrients and oxygen, as well as for heat dissipation. Physiological considerations for triathlon training and racing are in many ways similar to those underlying successful performance of single-event endurance activities. However, because of the combination of skills and energy demands, the triathlon remains a unique physiological stress. Much remains to be investigated regarding the optimal physiological adaptations necessary for optimal and safe triathlon performance.

ISSN:0112-1642    

DOI:10.2165/00007256-199519040-00003

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryMiddle distance running involves popular race distances with performance dependent on a number of physiological factors. The physiological characteristics of successful runners are different from those of sprinters and long distance runners. Maximal oxygen uptake (V̇O2max), running economy and the anaerobic threshold are variables that have been shown to limit performance during long distance running, and rapid velocity and anaerobic variables have been shown to limit performance during sprinting. Success with middle distance running is dependent on an integrative contribution from aerobic and anaerobic variables which allows a runner to maintain a rapid velocity during a race. The relative contributions of the 2 energy systems are functions of distance, intensity and the physiological abilities of the runner. Middle distance runners can be successful with physiological profiles that include a variety of aerobic and anaerobic capabilities, and this characteristic separates them from long distance runners.

ISSN:0112-1642    

DOI:10.2165/00007256-199519040-00004

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryThe endocrine equilibrium which regulates reproductive function in women can be affected by physical and psychological factors. Blood levels of hormones depend on a balance between production, metabolism and clearance rates. Intensive physical exercise may affect this balance via different mechanisms, such as stress associated with competition, dieting, reduction of body fat and body weight, production of heat or hypoxia.Women who engage in regular high intensity exercise may be at risk, as a consequence of these hormonal changes, of developing menstrual disturbances such as oligomenorrhoea, delayed menarche and amenorrhoea. Impaired production of gonadotrophins, which leads to luteal phase deficiency and anovulation, is a common hormonal finding with exercise-induced menstrual disturbances, but several other hormones may show significant alterations.In this article we have reviewed the recent literature on the effects of intensive physical exercise on the menstrual cycle, on some important physical parameters such as bone mineral density and bodyweight, and on those hormones (gonadotrophins, prolactin, melatonin, opioid peptides and steroids) which regulate, directly or indirectly, the reproductive function in women.

ISSN:0112-1642    

DOI:10.2165/00007256-199519040-00005

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryFemale athletes are at increased risk for certain sports-related injuries, particularly those involving the knee. Factors that contribute to this increased risk are the differences in sports undertaken and in gender anatomy and structure. Gender differences include baseline level of conditioning, lower extremity alignment, physiological laxity, pelvis width, tibial rotation and foot alignment. Sports like gymnastics and cheerleading create a noncontact environment, but can result in significant knee injuries. In quick stopping and cutting sports, females have an increased incidence of anterior cruciate ligament (ACL) injury by noncontact mechanisms. Patellofemoral (PF) disorders are also very common in female athletes.Awareness of these facts helps the sports medicine professional make an accurate diagnosis and institute earlier treatment-focused rehabilitation with or without surgery. Further prospective and retrospective research is needed in areas of epidemiology, mechanisms, severity and types of knee injuries. The goal is to lessen the severity of certain knee injuries and to prevent others.

ISSN:0112-1642    

DOI:10.2165/00007256-199519040-00006

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS