Applied physiology of a triathlon

Nociceptive Processing of Elite Athletes Varies between Sport-Specific Loads: An EEG-Based Study Approach

INTRODUCTION

For the downstream nociceptive processing of elite athletes, recent studies indicate that athletes probably tolerate more pain as compared with a normally active population. Phenotyping the nociceptive processing of athletes in different types of endurance sports can provide insight into training-specific effects, which may help in understanding the long-term effects of specific exercise.

METHODS

Twenty-six elite endurance athletes from the disciplines of rowing, triathlon, and running and 26 age- and sex-matched, recreationally active control subjects who participated in the subjective pain perception and processing of standardized noxious stimuli were investigated by EEG. This included standardized heat pain thresholds (HPT) and contact heat-evoked potentials from heat stimulation, measured with EEG as well as pinprick-evoked potentials from mechanical stimulation.

RESULTS

After noxious stimulation, athletes showed a higher activation of the event-related spectral perturbation (ERSP) patterns in the N2P2 EEG response at the Cz Electrode compared with the controls. After noxious contact heat stimulation, triathletes had a higher ERSP activation compared with the controls, whereas the rowers had a higher ERSP activation after noxious mechanical stimulation. Also, HPT in triathletes were increased despite their increased central activation after thermal stimulation. We found a correlation between increased HPT and training hours and years, although athletes did not differ within these variables.

CONCLUSIONS

Although we were able to identify differences between athletes of different endurance sports, the reasons and implications of these differences remain unclear. The study of sport-specific somatosensory profiles may help to understand the mechanisms of exercise-related long-term effects on pain processing and perception. Furthermore, sport-specific somatosensory effects may support the personalization of exercise interventions and identify risk factors for chronic pain in elite athletes.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise

In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.

Lactobacillus plantarum PS128 Improves Physiological Adaptation and Performance in Triathletes through Gut Microbiota Modulation

A triathlon is an extremely high-intensity exercise and a challenge for physiological adaptation. A triathlete's microbiome might be modulated by diet, age, medical treatments, lifestyle, and exercise, thereby maintaining aerobiosis and optimum health and performance. Probiotics, prebiotics, and synbiotics have been reported to have health-promoting activities (e.g., immunoregulation and cancer prevention). However, few studies have addressed how probiotics affect the microbiota of athletes and how this translates into functional activities. In our previous study, we found that Lactobacillus plantarum PS128 could ameliorate inflammation and oxidative stress, with improved exercise performance. Thus, here we investigate how the microbiota of triathletes are altered by L. plantarum PS128 supplementation, not only for exercise performance but also for possible physiological adaptation. The triathletes were assigned to two groups: an L. plantarum 128 supplement group (LG, 3 × 10¹⁰ colony-forming units (CFU)/day) and a placebo group (PG). Both groups continued with their regular exercise training for the next 4 weeks. The endurance performance, body composition, biochemistries, blood cells, microbiota, and associated metabolites were further investigated. PS128 significantly increased the athletes' endurance, by about 130% as compared to the PG group, but there was no significant difference in maximal oxygen consumption (VO₂max) and composition between groups. The PS128 supplementation (LG) modulated the athlete's microbiota with both significant decreases (Anaerotruncus, Caproiciproducens, Coprobacillus, Desulfovibrio, Dielma, Family_XIII, Holdemania, and Oxalobacter) and increases (Akkermansia, Bifidobacterium, Butyricimonas, and Lactobacillus), and the LG showed lower diversity when compared to the PG. Also, the short-chain fatty acids (SCFAs; acetate, propionate, and butyrate) of the LG were significantly higher than the PG, which might be a result of a modulation of the associated microbiota. In conclusion, PS128 supplementation was associated with an improvement on endurance running performance through microbiota modulation and related metabolites, but not in maximal oxygen uptake.

Effects of Competitive Triathlon Training on Telomere Length

Telomeres act as a mitotic clock and telomere-related senescence has been linked to age-related physiological decline. There is increasing evidence lifestyle factors can influence telomere length (TL). The purpose of this study was to determine the effect of competitive triathlon training on TL. Seven competitive male triathletes and seven recreationally active males participated in the study. Relative TL was measured using quantitative polymerase chain reaction. Physiological parameters key to athletic performance such as maximal oxygen intake, lactate threshold, and running economy were also measured. Triathletes had longer telomeres than the recreationally active (1.257 ± 0.028 vs. 1.002 ± 0.014; p < .0001). Positive association was found between TL and maximal oxygen intake, lactate threshold, and running economy (R² = .677, .683, and .696, respectively). This study indicates that competitive triathlon training buffers against age-related telomere shortening, and there is a correlation between exercise behaviors, higher maximal oxygen intake, and TL.

Sex Difference in Triathlon Performance

This brief review investigates how sex influences triathlon performance. Performance time for both Olympic distance and Ironman distance triathlons, and physiological considerations are discussed for both elite and non-elite male and female triathletes. The relative participation of female athletes in triathlon has increased over the last three decades, and currently represents 25-40% of the total field. Overall, the sex difference in both Olympic and Ironman distance triathlon performance has narrowed across the years. Sex difference differed with exercise mode and exercise duration. For non-elite Ironman triathletes, the sex difference in swimming time (≈12%) is lower than that which was evidenced for cycling (≈15%) and running (≈18%). For elite triathletes, sex difference in running performance is greater for Olympic triathlon (≈14%) than it is for Ironman distance triathlon (≈7%). Elite Ironman female triathletes have reduced the gap to their male counterparts to less than 10% for the marathon. The sex difference in triathlon performance is likely to be due to physiological (e.g., VO2max) and morphological (e.g., % body fat) factors but hormonal, psychological and societal (e.g., lower participation rate) differences should also be considered. Future studies should address the limited evidence relating sex difference in physiological characteristics such as lactate threshold, exercise economy or peak fat oxidation.

Can strenuous exercise harm the heart? Insights from a study of cardiovascular neural regulation in amateur triathletes

Regular exercise is recommended to improve the cardiovascular risk profile. However, there is growing evidence that extreme volumes and intensity of long-term exertion may increase the risk of acute cardiac events. The aim of this study is to investigate the after-effects of regular, strenuous physical training on the cardiovascular neural regulation in a group of amateur triathletes compared to age-matched sedentary controls. We enrolled 11 non-elite triathletes (4 women, age 24±4 years), who had refrained from exercise for 72 hours, and 11 age-matched healthy non-athletes (3 women, age 25±2 years). Comprehensive echocardiographic and cardiopulmonary exercise tests were performed at baseline. Electrocardiogram, non-invasive blood pressure, respiratory activity, and muscle sympathetic nerve activity (MSNA) were continuously recorded in a supine position (REST) and during an incremental 15° step-wise head-up tilt test up to 75° (TILT). Blood samples were collected for determination of stress mediators. Autoregressive spectral analysis provided the indices of the cardiac sympathetic (LF_RR) and vagal (HF_RR) activity, the vascular sympathetic control (LF_SAP), and the cardiac sympatho-vagal modulation (LF/HF). Compared to controls, triathletes were characterized by greater LF_RR, LF/HF ratio, LF_SAP, MSNA, and lower HF_RR at REST and during TILT, i.e. greater overall cardiovascular sympathetic modulation together with lower cardiac vagal activity. Cortisol and adrenocorticotropic hormone concentrations were also higher in triathletes. In conclusion, triathletes were characterized by signs of sustained cardiovascular sympathetic overactivity. This might represent a risk factor for future cardiovascular events, given the known association between chronic excessive sympathetic activity and increased cardiovascular risk.

Swimming and the heart

Exercise training is accepted to be beneficial in lowering morbidity and mortality in patients with cardiac disease. Swimming is a popular recreational activity, gaining recognition as an effective option in maintaining and improving cardiovascular fitness. Swimming is a unique form of exercise, differing from land-based exercises such as running in many aspects including medium, position, breathing pattern, and the muscle groups used. Water immersion places compressive forces on the body with resulting physiologic effects. We reviewed the physiologic effects and cardiovascular responses to swimming, the cardiac adaptations to swim training, swimming as a cardiac disease risk factor modifier, and the effects of swimming in those with cardiac disease conditions such as coronary artery disease, congestive heart failure and the long-QT syndrome.

Age-related changes in ultra-triathlon performances

Background

The age-related decline in performance has been investigated in swimmers, runners and triathletes. No study has investigated the age-related performance decline in ultra-triathletes. The purpose of this study was to analyse the age-related declines in swimming, cycling, running and overall race time for both Triple Iron ultra-triathlon (11.4-km swimming, 540-km cycling and 126.6-km running) and Deca Iron ultra-triathlon (38-km swimming, 1,800-km cycling and 420-km running).

Methods

The age and performances of 423 male Triple Iron ultra-triathletes and 119 male Deca Iron ultra-triathletes were analysed from 1992 to 2010 using regression analyses and ANOVA.

Results

The mean age of the finishers was significantly higher for Deca Iron ultra-triathletes (41.3 ± 3.1 years) compared to a Triple Iron ultra-triathletes (38.5 ± 3.3 years) (P < 0.05). For both ultra-distances, the fastest overall race times were achieved between the ages of 25 and 44 years. Deca Iron ultra-triathletes achieved the same level of performance in swimming and cycling between 25 and 54 years of age.

Conclusions

The magnitudes of age-related declines in performance in the three disciplines of ultra-triathlon differ slightly between Triple and Deca Iron ultra-triathlon. Although the ages of Triple Iron ultra-triathletes were on average younger compared to Deca Iron ultra-triathletes, the fastest race times were achieved between 25 and 44 years for both distances. Further studies should investigate the motivation and training of ultra-triathletes to gain better insights in ultra-triathlon performance.

Age and gender differences in half-Ironman triathlon performances - the Ironman 70.3 Switzerland from 2007 to 2010

Background

To date, the age-related decline and gender differences in performance have been investigated for both Olympic and Ironman distance triathlons, but not for the intermediate distance (ie, the half-Ironman distance triathlon covering 1.9 km swimming, 90 km cycling and 21.1 km running, Ironman 70.3®). We determined the age-related differences in performance and the gender differences for female and male half-Ironman triathletes of 6303 finishers (1115 women and 5188 men) at the Ironman 70.3 Switzerland in Rapperswil, Switzerland, from 2007 to 2010.

Methods

Analyses of variance were used to examine performance trends and differences between the genders.

Results

Gender differences in total event time were affected by age (F = 4.2; P < 0.001). Women achieved their best performance between 25 and 39 years whereas men attained their fastest race times between 18 and 39 years. The gender difference for ages 18–24 years was significantly (P < 0.01) greater compared to older age groups (25–29 years and 40–44 years), and the gender difference for age groups 45–49 years and 50–54 years was significantly (P < 0.01) greater than for those between the ages of 35–39 years.

Conclusion

The present data suggest that the fastest race time in a half-Ironman triathlon was achieved between the age of 25 and 39 years for women and between 18 and 39 years for men. Further studies considering the influences on endurance performance are required to better understand the age and gender interactions in half-Ironman triathlon performances, and these studies may provide valuable information to delineate the difference in performance between female and male half-Ironman triathletes.

European athletes dominate performances in Double Iron ultra-triathlons--a retrospective data analysis from 1985 to 2010

We investigated the participation and performance trends of ultra-endurance triathletes from all nationalities competing in a Double Iron ultra-triathlon (7.6-km swim, 360-km cycle and 84.4-km run) from 1985 to 2010. A total of 1854 athletes participated in 92 Double Iron ultra-triathlons. The majority of the winners came from Europe with 72 victories, followed by North America with 17 victories. The race time for the European ultra-triathletes was 1340 (s=95.3) min, decreasing highly significantly (r (2)=0.28; P<0.0001) across the years. North American ultra-triathletes finished the races within 1556 (s=124.5) min; their race time showed no changes across the years (r (2)=0.045; P=0.07). The race time for the Europeans was highly significantly faster compared to the North Americans (P<0.0001). Future studies should investigate each country in Europe and North America in order to find the country with the largest participation of athletes and their best performance.

The relationships between science and sport: application in triathlon

The relationships between sport sciences and sports are complex and changeable, and it is not clear how they reciprocally influence each other. By looking at the relationship between sport sciences and the "new" (~30-year-old) sport of triathlon, together with changes in scientific fields or topics that have occurred between 1984 and 2006 (278 publications), one observes that the change in the sport itself (eg, distance of the events, wetsuit, and drafting) can influence the specific focus of investigation. The sport-scientific fraternity has successfully used triathlon as a model of prolonged strenuous competition to investigate acute physiological adaptations and trauma, as support for better understanding cross-training effects, and, more recently, as a competitive sport with specific demands and physiological features. This commentary discusses the evolution of the scientific study of triathlon and how the development of the sport has affected the nature of scientific investigation directly related to triathlon and endurance sport in general.

Triathlon related musculoskeletal injuries: The status of injury prevention knowledge

Triathlon is a popular participation sport that combines swimming, cycling and running into a single event. A number of studies have investigated the incidence of injury, profile of injuries sustained and factors contributing to triathlon injury. This paper summarises the published literature in the context of the evidence base for the prevention of triathlon related injuries. Relevant articles on triathlon injuries were sourced from peer-reviewed English language journals and assessed using the Translating Research into Injury Prevention Practice (TRIPP) framework. This review highlights the significant knowledge gap that exists in the published literature describing the incidence of injury, the profile of injuries sustained and evidence for the prevention of injury in triathlon. Despite the number of studies undertaken to address TRIPP Stages 1 and 2 (injury surveillance, aetiology and mechanism of injury), most triathlon studies have been limited by retrospective designs with substantial, and unvalidated, recall periods, inconsistency in the definitions used for a reportable injury and exposure to injury, or a failure to capture exposure data at all. Overall, the paucity of quality, prospective studies investigating the incidence of injury in triathlon and factors contributing to their occurrence has led to an inability to adequately inform the development of injury prevention strategies (TRIPP Stages 3-6) for this sport, a situation that must be rectified if gains are to be made in reducing the burden of triathlon related injury.

Comparação de respostas fisiológicas absolutas e relativas entre ciclistas e triatletas

FUNDAMENTOS E OBJETIVO: O limiar anaeróbio, que pode ser determinado a partir do método ventilatório, tem sido proposto como um marcador de capacidade e como referência para prescrição de treinamento em exercícios de resistência aeróbia. O objetivo deste estudo foi comparar o consumo máximo de oxigênio (VO2MÁX) e o limiar ventilatório (LV) de ciclistas e triatletas, durante teste em cicloergômetro. MÉTODOS: Doze atletas do ciclismo e 13 atletas do triatlo foram submetidos a um teste de esforço máximo, para a determinação do VO2MÁX e LV, que foi mensurado por meio de medida direta, utilizando um ergoespirômetro. O valor do VO2MÁX foi considerado o maior valor mantido durante 30 segundos consecutivos durante o teste. Os equivalentes ventilatórios de oxigênio e de dióxido de carbônico, a pressão parcial de oxigênio e a pressão parcial de CO2 (P ET CO2) foram plotados em um gráfico, em função da carga. A partir desses gráficos, o LV foi determinado usando o critério do aumento dos equivalentes ventilatórios com concomitante redução na P ET CO2. RESULTADOS E CONCLUSÃO: Houve diferença (p < 0,05) para o VO2MÁX (57,72 ± 3,92 e 49,47 ± 5,96kg·ml-1·min-1), VO2 no LV (46,91 ± 5,96 e 42,16 ± 4,97kg·ml-1·min-1) e freqüência cardíaca máxima (FC MÁX) (188,83 ± 12,89 e 174,61 ± 13,79bpm) entre ciclistas e triatletas, respectivamente. Entretanto, não houve diferença para o %VO2MÁX no LV (81,42 ± 7,61 e 85,18 ± 6,87%), freqüência cardíaca correspondente ao LV (168,5 ± 13,79 e 157,23 ± 16,15bpm) e %FC MÁX no LV (89,23 ± 6,98 e 90,05 ± 1,04%) entre ciclistas e triatletas. Concluiu-se que ciclistas e triatletas apresentaram diferenças quanto ao seu condicionamento aeróbio, pois apresentaram adaptações fisiológicas distintas.

Effective force and economy of triathletes and cyclists

The effective force applied on the crank, the index of pedalling effectiveness, and the economy of movement at 60, 75, 90, and 105 rev/min cadences were examined in nine cyclists and eight triathletes. Tests were performed on two days. Maximal oxygen uptake was measured and the second ventilatory threshold was estimated on day 1 using a stationary bicycle. On day 2, the four different cadences were tested at about 5% below the second ventilatory threshold. A strain gauge instrumented clip-less pedal mounted on the bicycle enabled us to measure the normal and tangential forces exerted on the pedal, while the pedal and crank angles were monitored with the aid of a video system. Based on this information, the effective force and the index of pedalling effectiveness were calculated. Cyclists produced significantly more effective force and a higher index of pedalling effectiveness at 60 and 75 rev/min and were significantly more economic at all cadences than triathletes. The significant and positive correlation between effective force and economy at all cadences suggests that improvement of the effective force would reflect on economy.

Does prior 1500-m swimming affect cycling energy expenditure in well-trained triathletes?

The purpose of this study was to determine the effects of a 1,500-m swim on energy expenditure during a subsequent cycle task. Eight well-trained male triathletes (age 26.0 +/- 5.0 yrs; height 179.6 +/- 4.5 cm; mass 71.3 +/- 5.8 kg; VO(2)max 71.9 +/- 7.8 ml.kg(-1).min(-1)) underwent two testing sessions in counterbalanced order. The sessions consisted of a 30-min ride on the cycle ergometer at 75% of maximal aerobic power (MAP), and at a pedaling frequency of 95 rev.min(-1), preceded either by a 1,500-m swim at 1.20 m.s(-1) (SC trial) or by a cycling warm-up at 30% of MAP (C trial). Respiratory and metabolic data were collected between the 3rd and the 5th min, and between the 28th and 30th min of cycling. The main results indicated a significantly lower gross efficiency (13.0%) and significantly higher blood lactate concentration (56.4%), VO(2) (5.0%), HR (9.3%), VE (15.7%), and RF (19.9%) in the SC compared to the C trial after 5 min, p < 0.05. After 30 min, only VE (7.9%) and blood lactate concentration (43.9%) were significantly higher in the SC compared to the C trial, p < 0.05. These results confirm the increase in energy cost previously observed during sprint-distance triathlons and point to the importance of the relative intensity of swimming on energy demand during subsequent cycling.

Hemodynamic and autonomic changes induced by Ironman: prediction of competition time by blood pressure variability

We hypothesized that the extreme endurance exercise of an Ironman competition would lead to long-standing hemodynamic and autonomic changes. We investigated also the possibility of predicting competition performance from baseline hemodynamic and autonomic parameters. We have investigated 27 male athletes before competition, 1 h after, and then for the following week after the competition. The Task Force monitor was used to measure beat-to-beat hemodynamic and autonomic parameters during supine rest and active standing. Heart rate ( P < 0.001) was increased, and stroke index ( P = 0.011), systolic blood pressure ( P = 0.004), diastolic blood pressure ( P < 0.001), total peripheral resistance index ( P < 0.001), and baroreceptor reflex sensitivity ( P < 0.001) were decreased after the competition. The 0.05- to 0.17-Hz band of heart rate and blood pressure variability was increased ( P < 0.001 and P < 0.001, respectively), the 0.17- to 0.40-Hz band of heart rate interval variability was decreased after the competition ( P < 0.001). All parameters returned to baseline values 3 days after the competition. After the competition, the autonomic response to orthostasis was significantly impaired. The 0.05- to 0.17-Hz band of diastolic blood pressure variability before competition and weekly net exercise training, but not the other hemodynamic and autonomic parameters, were related to competition time in multivariate regression analysis (multiple r = 0.70, P < 0.001). The marked hemodynamic and autonomic changes after an ultraendurance race, which are compatible with myocardial depression in the face of sympathetic activation and reduction of afterload, return to baseline after only 1–3 days. Because the 0.05- to 0.17-Hz band of diastolic blood pressure variability contributes to the prediction of competition time, the analysis of blood pressure variability in the frequency domain deserves further study for the prediction of endurance capacity.

Relationship between laboratory-measured variables and heart rate during an ultra-endurance triathlon

The aim of the present study was to examine the relationship between the performance heart rate during an ultra-endurance triathlon and the heart rate corresponding to several demarcation points measured during laboratory-based progressive cycle ergometry and treadmill running. Less than one month before an ultra-endurance triathlon, 21 well-trained ultra-endurance triathletes (mean +/- s: age 35 +/- 6 years, height 1.77 +/- 0.05 m, mass 74.0 +/- 6.9 kg, = 4.75 +/- 0.42 l x min(-1)) performed progressive exercise tests of cycle ergometry and treadmill running for the determination of peak oxygen uptake (VO2peak), heart rate corresponding to the first and second ventilatory thresholds, as well as the heart rate deflection point. Portable telemetry units recorded heart rate at 60 s increments throughout the ultra-endurance triathlon. Heart rate during the cycle and run phases of the ultra-endurance triathlon (148 +/- 9 and 143 +/- 13 beats x min(-1) respectively) were significantly (P < 0.05) less than the second ventilatory thresholds (160 +/- 13 and 165 +/- 14 beats x min(-1) respectively) and heart rate deflection points (170 +/- 13 and 179 +/- 9 beats x min(-1) respectively). However, mean heart rate during the cycle and run phases of the ultra-endurance triathlon were significantly related to (r = 0.76 and 0.66; P < 0.01), and not significantly different from, the first ventilatory thresholds (146 +/- 12 and 148 +/- 15 beats x min(-1) respectively). Furthermore, the difference between heart rate during the cycle phase of the ultra-endurance triathlon and heart rate at the first ventilatory threshold was related to marathon run time (r = 0.61; P < 0.01) and overall ultra-endurance triathlon time (r = 0.45; P < 0.05). The results suggest that triathletes perform the cycle and run phases of the ultra-endurance triathlon at an exercise intensity near their first ventilatory threshold.

Effect of ultramarathon cycling on the heart rate in elite cyclists

OBJECTIVES

To analyse the heart rate (HR) response and estimate the ultraendurance threshold-the optimum maintainable exercise intensity of ultraendurance cycling-in ultraendurance elite cyclists competing in the Race across the Alps.

METHODS

HR monitoring was performed in 10 male elite cyclists during the first Race across the Alps in 2001 (distance: 525 km; cumulative altitude difference: 12 600 m) to investigate the exercise intensity of a cycle ultramarathon and the cardiopulmonary strains involved. Four different exercise intensities were defined as percentages of maximal HR (HR(max)) as follows: recovery HR (HR(re)), <70% of HR(max); moderate aerobic HR (HR(ma)), 70-80%; intense aerobic HR (HR(ia)), 80-90%; and high intensity HR (HR(hi)), >90%.

RESULTS

All athletes investigated finished the competition. The mean racing time was 27 hours and 25 minutes, and the average speed was 18.6 km/h. The mean HR(max) was 186 beats/min, and the average value of measured HRs (HR(average)) was 126 beats/min resulting in a mean HR(average)/HR(max) ratio of 0.68, which probably corresponds to the ultraendurance threshold. The athletes spent 53% (14 hours 32 minutes) of total race time within HR(re), 25% (6 hours 51 minutes) within HR(ma), 19% (5 hours 13 minutes) within HR(ia), and only 3% (49 minutes) within HR(hi), which shows the exercise intensity to be predominantly moderate (HR(re) + HR(ma) = 78% or 21 hours 23 minutes). The HR response was influenced by the course profile as well as the duration. In all subjects, exercise intensity declined significantly during the race, as indicated by a decrease in HR(average)/HR(max) of 23% from 0.86 at the start to 0.66 at the end.

CONCLUSIONS

A substantial decrease (10% every 10 hours) in the HR response is a general cardiovascular feature of ultramarathon cycling, suggesting that the ultraendurance threshold lies at about 70% of HR(max) in elite ultramarathon cyclists.

Coût énergétique de la course à pied lors de l'enchaînement spécifique d'un duathlon

The aim of the present study was to investigate the variability of the energy cost of running (Cr) during a simulated duathlon performed in outdoor conditions by elite duathletes. This duathlon consisted of 5 km of running, 30 km of cycling, and 5 km of running. The main result was the lack of significant difference in Cr between the two running bouts (210 + 10 mL d'O2 km−1•kg−1 vs. 217 ± 10 mL d'O2 km−1•kg−1). This result is different from those observed during a triathlon, where an increase of energy cost of running bout has been reported. Furthermore, during a short-distance duathlon performed by well-trained subjects, none of the physiological (ventilation alteration, metabolic changes, or dehydration) or biomechanical factors that are classically evoked in triathlon research to explain Cr variability seem to be affected by the run-cycle-run transition. These results seem to minimize the negative effect of the cycle-to-run transition during a short-duration event in well-trained subjects. Key words: duathlon, oxygen uptake, cycle-to-run transition, elite performance

[Effects of swimming with a wet suit on energy expenditure during subsequent cycling]

The aim of this study was to investigate the effects of swimming with a wetsuit on energy expenditure during subsequent cycling. Nine well-trained triathletes underwent three submaximal trials. The first trial (SC) consisted of a 750-m swim realised at a competition pace, followed by a 10-min cycling exercise at a power output corresponding to the ventilatory threshold . The two other trials were composed of the same cycling exercise, preceded either by a 750-m swim with a wetsuit (WSC) or by a cycling warm-up (Ctrl). The main results are that the WSC trial was characterised by significantly lower swimming cadence (-14%), heart rate (-11%), and lactate values (-47%) compared to the SC trial, p < 0.05. Moreover, cycling efficiency was significantly higher in the WSC trial compared to the SC trial (12.1% difference, p < 0.05). The lower relative intensity observed during swimming with a wetsuit suggest the relative importance of swimming condition on the total performance in a sprint triathlon.

Specific aspects of contemporary triathlon: implications for physiological analysis and performance

Triathlon competitions are performed over markedly different distances and under a variety of technical constraints. In 'standard-distance' triathlons involving 1.5km swim, 40km cycling and 10km running, a World Cup series as well as a World Championship race is available for 'elite' competitors. In contrast, 'age-group' triathletes may compete in 5-year age categories at a World Championship level, but not against the elite competitors. The difference between elite and age-group races is that during the cycle stage elite competitors may 'draft' or cycle in a sheltered position; age-group athletes complete the cycle stage as an individual time trial. Within triathlons there are a number of specific aspects that make the physiological demands different from the individual sports of swimming, cycling and running. The physiological demands of the cycle stage in elite races may also differ compared with the age-group format. This in turn may influence performance during the cycle leg and subsequent running stage. Wetsuit use and drafting during swimming (in both elite and age-group races) result in improved buoyancy and a reduction in frontal resistance, respectively. Both of these factors will result in improved performance and efficiency relative to normal pool-based swimming efforts. Overall cycling performance after swimming in a triathlon is not typically affected. However, it is possible that during the initial stages of the cycle leg the ability of an athlete to generate the high power outputs necessary for tactical position changes may be impeded. Drafting during cycling results in a reduction in frontal resistance and reduced energy cost at a given submaximal intensity. The reduced energy expenditure during the cycle stage results in an improvement in running, so an athlete may exercise at a higher percentage of maximal oxygen uptake. In elite triathlon races, the cycle courses offer specific physiological demands that may result in different fatigue responses when compared with standard time-trial courses. Furthermore, it is possible that different physical and physiological characteristics may make some athletes more suited to races where the cycle course is either flat or has undulating sections. An athlete's ability to perform running activity after cycling, during a triathlon, may be influenced by the pedalling frequency and also the physiological demands of the cycle stage. The technical features of elite and age-group triathlons together with the physiological demands of longer distance events should be considered in experimental design, training practice and also performance diagnosis of triathletes.

Physiological demands of running during long distance runs and triathlons

The aim of this review article is to identify the main metabolic factors which have an influence on the energy cost of running (Cr) during prolonged exercise runs and triathlons. This article proposes a physiological comparison of these 2 exercises and the relationship between running economy and performance. Many terms are used as the equivalent of 'running economy' such as 'oxygen cost', 'metabolic cost', 'energy cost of running', and 'oxygen consumption'. It has been suggested that these expressions may be defined by the rate of oxygen uptake (VO2) at a steady state (i.e. between 60 to 90% of maximal VO2) at a submaximal running speed. Endurance events such as triathlon or marathon running are known to modify biological constants of athletes and should have an influence on their running efficiency. The Cr appears to contribute to the variation found in distance running performance among runners of homogeneous level. This has been shown to be important in sports performance, especially in events like long distance running. In addition, many factors are known or hypothesised to influence Cr such as environmental conditions, participant specificity, and metabolic modifications (e.g. training status, fatigue). The decrease in running economy during a triathlon and/or a marathon could be largely linked to physiological factors such as the enhancement of core temperature and a lack of fluid balance. Moreover, the increase in circulating free fatty acids and glycerol at the end of these long exercise durations bear witness to the decrease in Cr values. The combination of these factors alters the Cr during exercise and hence could modify the athlete's performance in triathlons or a prolonged run.

Hematocrits of triathletes: is monitoring useful?

PURPOSE

The purpose of this manuscript was to provide a basis for establishing safety cutoffs for hematocrit levels in triathletes and background data for possible future medical control regulations.

METHODS

Competitors from three different distance triathlons participated: Olympic (N = 118), half-Ironman (N = 87), and Ironman (N = 207). Blood samples were drawn within 24-36 h prerace (N = 412) and within minutes of race finish (N = 296). Prerace hematocrits approximated a normal distribution for men (X = 43.2 +/- 2.9) and women (X = 40.2+/-2.6). Prerace hematocrits decreased as competitive distance increased for men (X = 45.0, 43.4, 42.5; respectively; P < 0.01) but not for women (P > 0.05).

RESULTS

Mean race day changes were small but statistically significant for Olympic and Ironman men and for half-Ironman women. Individual responses were more variable with hemoconcentration occurring in 57%, hemodilution in 43%, and no change in 2% of participants. The magnitude of individual responses was also variable with hematocrit changes ranging from -7.1 to + 10%. No athlete in this sample had a hematocrit that would place him/her in the "danger zone" (Hct > 55%).

CONCLUSIONS

Cutoff values (3 SD above the means) of 52% for men and 48% for women are suggested by these data. However, the relationship of these cutoffs to either athlete safety or the ability to detect rules violations remains unknown.

Ventilation and entrainment of breathing during cycling and running in triathletes

PURPOSE

To assess whether entrainment of breathing (E) during exercise: 1) differed according to the test protocol in well-trained triathletes, and 2) improved ventilatory efficiency during exercise.

METHODS

Eight triathletes performed three incremental tests until exhaustion: while cycling (CE), while running at increasing grade and constant speed (increasing GRADE) and while running at increasing speed and constant grade (increasing SPEED), respectively. E was evaluated as the percentage of breaths occurring at respiratory rates (F) corresponding to integer ratios of the exercise cycle rate. To assess whether E improved ventilatory efficiency, deltaVE/VO2 between nonentrained and entrained breaths was measured at each load.

RESULTS

Mean E was higher in CE (57.2+/-21.9%) than in increasing GRADE (46.9+/-18.7%) and increasing SPEED (41.4+/-17.2%). E decreased at high loads in CE and increasing SPEED but not in increasing GRADE. In the group of subjects, E correlated with the degree of fitness (evaluated as VO2Tvent/VO2peak%) only during increasing GRADE. By multiple regression analysis on all data, minute ventilation correlated with CO2 production but not with the exercise cycle rate; however, either F or tidal volume correlated significantly with both these variables. VE/VO2 was lower in entrained than nonentrained breaths at each load in CE and increasing GRADE experiments, but the difference was small.

CONCLUSIONS

In spite of some differences among protocols, triathletes showed significant E during incremental exercise tests. Spontaneous E appeared to slightly improve ventilatory efficiency during CE and increasing GRADE protocols.

[Factors limiting performance in the triathlon]

Triathlon is a multievent sport (swimming, cycling, running). Long duration triathlons can induce physiological stress that can be modulated by environmental conditions. Certain factors promote performance, others limit it. A minimal level of maximal oxygen uptake is required, but it does not always determine the performance. For triathletes, the low hematocrit values do not reflect anemia and therefore do not limit performance. The appearance of clinical signs of dehydration and of digestive impairment may limit performance. The performance in swimming does not play the most important role in triathlon performance, but the physiological conditions in which the first transition is made can limit performance in the two following events; this is also the case for the second transition. Triathlon races cause muscle damage whose signs persist several days. Given the hormonal responses and the indices of muscle damage, it appears necessary to rest at least 5 days to avoid over-training. It is difficult to define precisely how much one should train for each of the three events. However, it can be concluded that triathlon training has to be taken as a whole.

Overtraining: consequences and prevention

Overtraining refers to prolonged fatigue and reduced performance despite increased training. Its roots include muscle damage, cytokine actions, the acute phase response, improper nutrition, mood disturbances, and diverse consequences of stress hormone responses. The clinical features are varied, non-specific, anecdotal and legion. No single test is diagnostic. The best treatment is prevention, which means (1) balancing training and rest, (2) monitoring mood, fatigue, symptoms and performance, (3) reducing distress and (4) ensuring optimal nutrition, especially total energy and carbohydrate intake.

Applied physiology of triathlon

The 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, VO2max), economy of motion (submaximal VO2) and fractional utilisation of maximal capacity (%VO2max) reflect the integrated responses of these physiological adaptations. Numerous studies have reported relatively high mean VO2max 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, VO2max is related to performance in the corresponding event of the triathlon (e.g. tethered swimming VO2max with swim time). In longer events and with more elite triathletes, VO2max correlates less well with performance. The physiological adaptations that correspond to and facilitate improved VO2max occur 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 VO2max in 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 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 of %VO2max.(ABSTRACT TRUNCATED AT 400 WORDS)

Biological responses to overload training in endurance sports

Five subjects undertook 10 days of twice daily interval training sessions on a treadmill followed by 5 days of active recovery. On days 1, 6, 11, and 16 the subjects were required to undertake a test of submaximal and maximal work capacity on a treadmill combined with a performance test consisting of a run to exhaustion with the treadmill set at 18 km.h-1 and 1% gradient. Also on these days a pre-exercise blood sample was collected and analysed for a range of haematological, biochemical and immunological parameters. The subjects experienced a significant fall in performance on day 11 which had returned to pretraining levels on day 16. Serum ferritin concentrations were depressed significantly from pretraining concentrations at the conclusion of the recovery period while the expression of lymphocyte activation antigens (CD25+ and HLA-DR+) was increased both after the training phase and the recovery phase. The number of CD56+ cells in the peripheral circulation was depressed at the conclusion of the recovery period. Several parameters previously reported to change in association with overload training failing to reflect the decrease in performance experienced by subjects in this study, suggesting that overtraining may best be diagnosed through a multifactorial approach to the recognition of symptoms. The most important factor to consider may be a decrease in the level of performance following a regeneration period. The magnitude of this decreased performance necessary for the diagnosis of overtraining and the nature of an "appropriate" regeneration period are, however, difficult to define and may vary depending upon the training background of the subjects and the nature of the preceding training. It may or may not be associated with biochemical, haematological, physiological and immunological indicators. Individual cases may present a different range of symptoms and diagnosis of overtraining should not be excluded based on the failure of blood parameters to demonstrate variation. However, blood parameters may be useful to identify possible aetiology in each separate case report of over-training. An outstanding factor to emerge from this study was the difficulty associated with an objective diagnosis of overtraining and this is a possible reason why there have been new accounts of overtraining research in the literature.