Breathing pattern in highly competitive cyclists during incremental exercise

Breathing Motion Pattern in Cyclists: Role of Inferior against Superior Thorax Compartment

The thoracoabdominal breathing motion pattern is being considered in sports training because of its contribution, along with other physiological adaptations, to overall performance. We examined whether and how experience with cycling training modifies the thoracoabdominal motion patterns. We utilized optoelectronic plethysmography to monitor ten trained male cyclists and compared them to ten physically active male participants performing breathing maneuvers. Cyclists then participated in a self-paced time trial to explore the similarity between that observed during resting breathing. From the 3D coordinates of 32 markers positioned on each participant's trunk, we calculated the percentage of contribution of the superior thorax, inferior thorax, and abdomen and the correlation coefficient among these compartments. During the rest maneuvers, the cyclists showed a thoracoabdominal motion pattern characterized by an increased role of the inferior thorax relative to the superior thorax (26.69±5.88%, 34.93±5.03%; p=0.002, respectively), in contrast to the control group (26.69±5.88%; 25.71±6.04%, p=0.4, respectively). In addition, the inferior thorax showed higher coordination in phase with the abdomen. Furthermore, the results of the time trial test underscored the same pattern found in cyclists breathing at rest, suggesting that the development of a permanent modification in respiratory mechanics may be associated with cycling practice.

Breathing Pattern Response after 6 Weeks of Inspiratory Muscle Training during Exercise

(1) Background: The breathing pattern is defined as the relationship between the tidal volume (VT) and breathing frequency (BF) for a given VE. The aim of this study was to evaluate whether inspiratory muscle training influenced the response of the breathing pattern during an incremental effort in amateur cyclists. (2) Methods: Eighteen amateur cyclists completed an incremental test to exhaustion, and a gas analysis on a cycle ergometer and spirometry were conducted. Cyclists were randomly assigned to two groups (IMTG = 9; CON = 9). The IMTG completed 6 weeks of inspiratory muscle training (IMT) using a PowerBreathe K3® device at 50% of the maximum inspiratory pressure (Pimax). The workload was adjusted weekly. The CON did not carry out any inspiratory training during the experimental period. After the 6-week intervention, the cyclists repeated the incremental exercise test, and the gas analysis and spirometry were conducted. The response of the breathing pattern was evaluated during the incremental exercise test. (3) Results: The Pimax increased in the IMTG (p < 0.05; d = 3.1; +19.62%). Variables related to the breathing pattern response showed no differences between groups after the intervention (EXPvsCON; p > 0.05). Likewise, no differences in breathing pattern were found in the IMTG after training (PREvsPOST; p > 0.05). (4) Conclusions: IMT improved the strength of inspiratory muscles and sport performance in amateur cyclists. These changes were not attributed to alterations in the response of the breathing pattern.

Accuracy of respiratory gas variables, substrate, and energy use from 15 CPET systems during simulated and human exercise

PURPOSE

Various systems are available for cardiopulmonary exercise testing (CPET), but their accuracy remains largely unexplored. We evaluate the accuracy of 15 popular CPET systems to assess respiratory variables, substrate use, and energy expenditure during simulated exercise. Cross-comparisons were also performed during human cycling experiments (i.e., verification of simulation findings), and between-session reliability was assessed for a subset of systems.

METHODS

A metabolic simulator was used to simulate breath-by-breath gas exchange, and the values measured by each system (minute ventilation [V̇E], breathing frequency [BF], oxygen uptake [V̇O2 ], carbon dioxide production [V̇CO2 ], respiratory exchange ratio [RER], energy from carbs and fats, and total energy expenditure) were compared to the simulated values to assess the accuracy. The following manufacturers (system) were assessed: COSMED (Quark CPET, K5), Cortex (MetaLyzer 3B, MetaMax 3B), Vyaire (Vyntus CPX, Oxycon Pro), Maastricht Instruments (Omnical), MGC Diagnostics (Ergocard Clinical, Ergocard Pro, Ultima), Ganshorn/Schiller (PowerCube Ergo), Geratherm (Ergostik), VO2master (VO2masterPro), PNOĒ (PNOĒ), and Calibre Biometrics (Calibre).

RESULTS

Absolute percentage errors during the simulations ranged from 1.15%-44.3% for V̇E, 1.05-3.79% for BF, 1.10%-13.3% for V̇O2 , 1.07%-18.3% for V̇CO2 , 0.62%-14.8% for RER, 5.52%-99.0% for Kcal from carbs, 5.13%-133% for Kcal from fats, and 0.59%-12.1% for total energy expenditure. Between-session variation ranged from 0.86%-21.0% for V̇O2 and 1.14%-20.2% for V̇CO2 , respectively.

CONCLUSION

The error of respiratory gas variables, substrate, and energy use differed substantially between systems, with only a few systems demonstrating a consistent acceptable error. We extensively discuss the implications of our findings for clinicians, researchers and other CPET users.

Differential control of respiratory frequency and tidal volume during exercise

The lack of a testable model explaining how ventilation is regulated in different exercise conditions has been repeatedly acknowledged in the field of exercise physiology. Yet, this issue contrasts with the abundance of insightful findings produced over the last century and calls for the adoption of new integrative perspectives. In this review, we provide a methodological approach supporting the importance of producing a set of evidence by evaluating different studies together-especially those conducted in 'real' exercise conditions-instead of single studies separately. We show how the collective assessment of findings from three domains and three levels of observation support the development of a simple model of ventilatory control which proves to be effective in different exercise protocols, populations and experimental interventions. The main feature of the model is the differential control of respiratory frequency (f_R) and tidal volume (V_T); f_R is primarily modulated by central command (especially during high-intensity exercise) and muscle afferent feedback (especially during moderate exercise) whereas V_T by metabolic inputs. Furthermore, V_T appears to be fine-tuned based on f_R levels to match alveolar ventilation with metabolic requirements in different intensity domains, and even at a breath-by-breath level. This model reconciles the classical neuro-humoral theory with apparently contrasting findings by leveraging on the emerging control properties of the behavioural (i.e. f_R) and metabolic (i.e. V_T) components of minute ventilation. The integrative approach presented is expected to help in the design and interpretation of future studies on the control of f_R and V_T during exercise.

Restricted nasal-only breathing during self-selected low intensity training does not affect training intensity distribution

Introduction: Low-intensity endurance training is frequently performed at gradually higher training intensities than intended, resulting in a shift towards threshold training. By restricting oral breathing and only allowing for nasal breathing this shift might be reduced. Methods: Nineteen physically healthy adults (3 females, age: 26.5 ± 5.1 years; height: 1.77 ± 0.08 m; body mass: 77.3 ± 11.4 kg; VO₂peak: 53.4 ± 6.6 mL·kg^-1 min^-1) performed 60 min of self-selected, similar (144.7 ± 56.3 vs. 147.0 ± 54.2 W, p = 0.60) low-intensity cycling with breathing restriction (nasal-only breathing) and without restrictions (oro-nasal breathing). During these sessions heart rate, respiratory gas exchange data and power output data were recorded continuously. Results: Total ventilation (p < 0.001, η_p ² = 0.45), carbon dioxide release (p = 0.02, η_p ² = 0.28), oxygen uptake (p = 0.03, η_p ² = 0.23), and breathing frequency (p = 0.01, η_p ² = 0.35) were lower during nasal-only breathing. Furthermore, lower capillary blood lactate concentrations were found towards the end of the training session during nasal-only breathing (time x condition-interaction effect: p = 0.02, η_p ² = 0.17). Even though discomfort was rated marginally higher during nasal-only breathing (p = 0.03, η_p ² = 0.24), ratings of perceived effort did not differ between the two conditions (p ≥ 0.06, η_p ² = 0.01). No significant "condition" differences were found for intensity distribution (time spent in training zone quantified by power output and heart rate) (p ≥ 0.24, η_p ² ≤ 0.07). Conclusion: Nasal-only breathing seems to be associated with possible physiological changes that may help to maintain physical health in endurance athletes during low intensity endurance training. However, it did not prevent participants from performing low-intensity training at higher intensities than intended. Longitudinal studies are warranted to evaluate longitudinal responses of changes in breathing patterns.

Breath Tools: A Synthesis of Evidence-Based Breathing Strategies to Enhance Human Running

Running is among the most popular sporting hobbies and often chosen specifically for intrinsic psychological benefits. However, up to 40% of runners may experience exercise-induced dyspnoea as a result of cascading physiological phenomena, possibly causing negative psychological states or barriers to participation. Breathing techniques such as slow, deep breathing have proven benefits at rest, but it is unclear if they can be used during exercise to address respiratory limitations or improve performance. While direct experimental evidence is limited, diverse findings from exercise physiology and sports science combined with anecdotal knowledge from Yoga, meditation, and breathwork suggest that many aspects of breathing could be improved via purposeful strategies. Hence, we sought to synthesize these disparate sources to create a new theoretical framework called “Breath Tools” proposing breathing strategies for use during running to improve tolerance, performance, and lower barriers to long-term enjoyment.

Exploring the Anthropometric, Cardiorespiratory, and Haematological Determinants of Marathon Performance

Aim

We aimed to investigate the main anthropometric, cardiorespiratory and haematological factors that can determine marathon race performance in marathon runners.

Methods

Forty-five marathon runners (36 males, age: 42 ± 10 years) were examined during the training period for a marathon race. Assessment of training characteristics, anthropometric measurements, including height, body weight (n = 45) and body fat percentage (BF%) (n = 33), echocardiographic study (n = 45), cardiopulmonary exercise testing using treadmill ergometer (n = 33) and blood test (n = 24) were performed. We evaluated the relationships of these measurements with the personal best marathon race time (MRT) within a time frame of one year before or after the evaluation of each athlete.

Results

The training age regarding long-distance running was 9 ± 7 years. Training volume was 70 (50-175) km/week. MRT was 4:02:53 ± 00:50:20 h. The MRT was positively associated with BF% (r = 0.587, p = 0.001). Among echocardiographic parameters, MRT correlated negatively with right ventricular end-diastolic area (RVEDA) (r = -0.716, p < 0.001). RVEDA was the only independent echocardiographic predictor of MRT. With regard to respiratory parameters, MRT correlated negatively with maximum minute ventilation indexed to body surface area (VEmax/BSA) (r = -0.509, p = 0.003). Among parameters of blood test, MRT correlated negatively with haemoglobin concentration (r = -0.471, p = 0.027) and estimated haemoglobin mass (Hbmass) (r = -0.680, p = 0.002). After performing multivariate linear regression analysis with MRT as dependent variable and BF% (standardised β = 0.501, p = 0.021), RVEDA (standardised β = -0.633, p = 0.003), VEmax/BSA (standardised β = 0.266, p = 0.303) and Hbmass (standardised β = -0.308, p = 0.066) as independent variables, only BF% and RVEDA were significant independent predictors of MRT (adjusted R² = 0.796, p < 0.001 for the model).

Conclusions

The main physiological determinants of better marathon performance appear to be low BF% and RV enlargement. Upregulation of both maximum minute ventilation during exercise and haemoglobin mass may have a weaker effect to enhance marathon performance.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT04738877.

The effect of pedalling cadence on respiratory frequency: passive vs. active exercise of different intensities

PURPOSE

Pedalling cadence influences respiratory frequency (f_R) during exercise, with group III/IV muscle afferents possibly mediating its effect. However, it is unclear how exercise intensity affects the link between cadence and f_R. We aimed to test the hypothesis that the effect of cadence on f_R is moderated by exercise intensity, with interest in the underlying mechanisms.

METHODS

Ten male cyclists performed a preliminary ramp incremental test and three sinusoidal experimental tests on separate visits. The experimental tests consisted of 16 min of sinusoidal variations in cadence between 115 and 55 rpm (sinusoidal period of 4 min) performed during passive exercise (PE), moderate exercise (ME) and heavy exercise (HE). The amplitude (A) and phase lag (φ) of the dependent variables were calculated.

RESULTS

During PE, f_R changed in proportion to variations in cadence (r = 0.85, P < 0.001; A = 3.9 ± 1.4 breaths·min^-1; φ = - 5.3 ± 13.9 degrees). Conversely, the effect of cadence on f_R was reduced during ME (r = 0.73, P < 0.001; A = 2.6 ± 1.3 breaths·min^-1; φ = - 25.4 ± 26.3 degrees) and even more reduced during HE (r = 0.26, P < 0.001; A = 1.8 ± 1.0 breaths·min^-1; φ = - 70.1 ± 44.5 degrees). No entrainment was found in any of the sinusoidal tests.

CONCLUSION

The effect of pedalling cadence on f_R is moderated by exercise intensity-it decreases with the increase in work rate-and seems to be mediated primarily by group III/IV muscle afferents, at least during passive exercise.

Low Frequency Severe-Intensity Interval Training Markedly Alters Respiratory Compensation Point During Incremental Exercise in Untrained Male

This study investigated the effect of low-frequency severe-intensity interval training on the respiratory compensation point (RCP) during incremental exercise test. Eighteen healthy males (age; 20.7 ± 2.2 years, range 18 to 29 years, height; 174.0 ± 5.6 cm, weight; 68.8 ± 13.5 kg) were randomly assigned to an interval training group or a control group. Interval training was conducted once weekly for 3 months. Each session consisted of three bouts of bicycle ergometer exercise at 80% maximum work rate until volitional fatigue. Before (baseline) and after the 3-month intervention, incremental exercise test was performed on a bicycle ergometer for determination of ventilatory threshold (VT), RCP, and peak oxygen consumption (V̇_{O 2} peak). The training program resulted in significant increases of V̇_{O 2} peak (+ 14%, p < 0.001, η p 2 = 0.437), oxygen consumption (V̇_{O 2}) at VT (+ 18%, p < 0.001, η p 2 = 0.749) and RCP (+ 15%, p = 0.03, η p 2 = 0.239) during incremental exercise test in the training group. Furthermore, a significant positive correlation was observed between the increase in V̇_{O 2} peak and increase in V̇_{O 2} at RCP after intervention (r = 0.87, p = 0.002) in the training group. Tidal volumes at VT (p = 0.04, η p 2 = 0.270) and RCP (p = 0.01, η p 2 = 0.370) also increased significantly after intervention compared to baseline. Low-frequency severe-intensity interval training induced a shift in RCP toward higher work rate accompanied by higher tidal volume during incremental exercise test.

Ventilatory efficiency response is unaffected by fitness level, ergometer type, age or body mass index in male athletes

The aim of this study was to evaluate the ventilatory efficiency (V_E/VCO₂ slope) and the respiratory control (Vt/Ti slope) in a wide range of athletes and describe the influence of fitness level, age, ergometer type or BMI on these parameters. Ninety-one males (30.4±10.53 years; 175.52±7.45 cm; 71.99±9.35 kg) were analysed retrospectively for the study. Ventilatory efficiency reacted similarly in athletes independently of the fitness level, age, BMI or the ergometer used for testing. No significant differences were found in V_E/VCO₂ slope and the Vt/Ti slope between variables analyzed (P>0.05). The slope of the predictive equations was similar in all cases studied in V_E/VCO₂ slope and the Vt/Ti slope. Moreover, the central control impulse of respiration was not affected by the variables studied. These observations suggest that ventilatory efficiency (V_E/VCO₂ slope) could be a variable fixed by the respiratory system which tends to respond similarly in athletes.

Discriminant analysis of cardiovascular and respiratory variables for classification of road cyclists by specialty

BACKGROUND

Different variables determine the performance of cyclists, which brings up the question how these parameters may help in their classification by specialty. The aim of the study was to determine differences in cardiorespiratory parameters of male cyclists according to their specialty: flat riders (N.=21), hill riders (N.=35), or sprinters (N.=20) and obtain the multivariate model for further cyclists classification by specialties, based on selected variables.

METHODS

Seventeen variables were measured at submaximal and maximum load on the cycle ergometer Cosmed E 400HK (Cosmed, Rome, Italy) (initial 100 W with 25-W increase, 90-100 rpm). Multivariate discriminant analysis was used to determine which variables group cyclists within their specialty, and to predict which variables can direct cyclists to a particular specialty.

RESULTS

Among nine variables that statistically contribute to the discriminant power of the model, achieved power on the anaerobic threshold and the produced CO2 had the biggest impact. The obtained discriminatory model correctly classified 91.43% of flat riders, 85.71% of hill riders, while sprinters were classified completely correct (100%), i.e. 92.10% of examinees were correctly classified, which point out the strength of the discriminatory model.

CONCLUSIONS

Respiratory indicators mostly contribute to the discriminant power of the model, which may significantly contribute to training practice and laboratory tests in future.

Effects of detraining on breathing pattern and ventilatory efficiency in young soccer players

BACKGROUND

This study investigated the effects of detraining on breathing pattern. The aim of this study was to evaluate the effect of a six-week detraining period on breathing patterns and ventilatory efficiency.

METHODS

Fourteen young soccer players were evaluated at the end of a competitive season and after a six-week detraining period. Assessment of respiratory efficiency was based on VE/VCO2 slope changes below 70% of exercise intensity. All participants underwent twice an incremental graded exercise test up to exhaustion.

RESULTS

No differences in breathing frequency and inspiratory time/total time ratio (Ti/Ttot) were found after detraining (P>0.05). Differences in tidal volume (VT), VT/Ti quotient and VE were significant (P<0.05) at between 40 to 100% of exercise intensity. The VE/VCO2 slope did not change (P>0.05) during a postdetraining maximal incremental test.

CONCLUSIONS

A six-week detraining period causes changes in inspiratory flow but does not affect the inspiratory time/total respiratory cycle time ratio. The overall ventilatory efficiency of the respiratory system remains constant and is not affected by detraining.

The midpoint between ventilatory thresholds approaches maximal lactate steady state intensity in amateur cyclists

The aim was to determine whether the midpoint between ventilatory thresholds (MPVT) corresponds to maximal lactate steady state (MLSS). Twelve amateur cyclists (21.0 ± 2.6 years old; 72.2 ± 9.0 kg; 179.8 ± 7.5 cm) performed an incremental test (25 W·min^-1) until exhaustion and several constant load tests of 30 minutes to determine MLSS, on different occasions. Using MLSS determination as the reference method, the agreement with five other parameters (MPVT; first and second ventilatory thresholds: VT1 and VT2; respiratory exchange ratio equal to 1: RER = 1.00; and Maximum) was analysed by the Bland-Altman method. The difference between workload at MLSS and VT1, VT2, RER=1.00 and Maximum was 31.1 ± 20.0, -86.0 ± 18.3, -63.6 ± 26.3 and -192.3 ± 48.6 W, respectively. MLSS was underestimated from VT1 and overestimated from VT2, RER = 1.00 and Maximum. The smallest difference (-27.5 ± 15.1 W) between workload at MLSS and MPVT was in better agreement than other analysed parameters of intensity in cycling. The main finding is that MPVT approached the workload at MLSS in amateur cyclists, and can be used to estimate maximal steady state.

Efeito do treinamento sobre a eficiência ventilatória de indivíduos saudáveis

Introdução: Diversos índices de eficiência ventilatória (EV) têm fornecido uma medida extra para avaliação do condicionamento cardiorrespiratório em adição ao consumo de oxigênio (VO2) no pico do exercício e no nível do limiar ventilatório (VO2LV). Em indivíduos com insuficiência cardíaca já foi demonstrado que há aumento da EV após treinamento. No entanto, a sensibilidade dessa medida para avaliar o efeito do treinamento em indivíduos saudáveis foi pouco estudada.Objetivo: Testar a hipótese de que um programa de treinamento delineado para melhorar a condição aeróbia, também exerça alterações na eficiência ventilatória em indivíduos saudáveis.Métodos: 48 homens, aparentemente saudáveis e ativos (24±5 anos), foram submetidos a um teste cardiopulmonar de exercício (TCPE), antes e após 13 semanas de treinamento aeróbio, realizado três vezes por semana, durante 30 minutos com a intensidade inicial de 60-65% da FCmáx, gradualmente aumentada até o fim do programa para 85-90% da FCmax. Os parâmetros avaliados incluíram: VO2pico, VO2 no LV e EV determinada através do cálculo do slope da relação entre a ventilação e a produção de dióxido de carbono, por meio de regressão linear.Resultados: Houve um aumento de 12,5% no VO2LV (30,4±4,5 vs. 34,2±4,9 ml.kg-1.min-1, p<0,05) e de 10,9% no VO2pico (53,2±8,3 vs. 59±9,9 ml.kg-1.min-1, p<0,05), acompanhado de uma redução de 4,1% no slopeVE-VCO2 (25,2±3,3 vs. 24,2±3,7, p<0,05).Conclusão: A EV aumenta após o treinamento em homens saudáveis sugerindo que o slope da relação VE-VCO2 pode ser utilizado de forma adicional na monitoração dos efeitos do treinamento, complementando a interpretação da integração cardiorrespiratória do TCPE.

Erythropoietin doping in cycling: lack of evidence for efficacy and a negative risk-benefit

Imagine a medicine that is expected to have very limited effects based upon knowledge of its pharmacology and (patho)physiology and that is studied in the wrong population, with low-quality studies that use a surrogate end-point that relates to the clinical end-point in a partial manner at most. Such a medicine would surely not be recommended. The use of recombinant human erythropoietin (rHuEPO) to enhance performance in cycling is very common. A qualitative systematic review of the available literature was performed to examine the evidence for the ergogenic properties of this drug, which is normally used to treat anaemia in chronic renal failure patients. The results of this literature search show that there is no scientific basis from which to conclude that rHuEPO has performance-enhancing properties in elite cyclists. The reported studies have many shortcomings regarding translation of the results to professional cycling endurance performance. Additionally, the possibly harmful side-effects have not been adequately researched for this population but appear to be worrying, at least. The use of rHuEPO in cycling is rife but scientifically unsupported by evidence, and its use in sports is medical malpractice. What its use would have been, if the involved team physicians had been trained in clinical pharmacology and had investigated this properly, remains a matter of speculation. A single well-controlled trial in athletes in real-life circumstances would give a better indication of the real advantages and risk factors of rHuEPO use, but it would be an oversimplification to suggest that this would eradicate its use.

Evidence of break-points in breathing pattern at the gas-exchange thresholds during incremental cycling in young, healthy subjects

The present study investigated whether 'break-points' in breathing pattern correspond to the first ([Formula: see text]) and second gas-exchange thresholds ([Formula: see text]) during incremental cycling. We used polynomial spline smoothing to detect accelerations and decelerations in pulmonary gas-exchange data, which provided an objective means of 'break-point' detection without assumption of the number and shape of said 'break-points'. Twenty-eight recreational cyclists completed the study, with five individuals excluded from analyses due to low signal-to-noise ratios and/or high risk of 'pseudo-threshold' detection. In the remaining participants (n = 23), two separate and distinct accelerations in respiratory frequency (f (R)) during incremental work were observed, both of which demonstrated trivial biases and reasonably small ±95% limits of agreement (LOA) for the [Formula: see text] (0.2 ± 3.0 ml O(2) kg(-1) min(-1)) and [Formula: see text] (0.0 ± 2.4 ml O(2) kg(-1) min(-1)), respectively. A plateau in tidal volume (V (T)) data near the [Formula: see text] was identified in only 14 individuals, and yielded the most unsatisfactory mean bias ±LOA of all comparisons made (-0.4 ± 5.3 ml O(2) kg(-1) min(-1)). Conversely, 18 individuals displayed V (T)-plateau in close proximity to the [Formula: see text] evidenced by a mean bias ± LOA of 0.1 ± 3.1 ml O(2) kg(-1) min(-1). Our findings suggest that both accelerations in f (R) correspond to the gas-exchange thresholds, and a plateau (or decline) in V (T) at the [Formula: see text] is a common (but not universal) feature of the breathing pattern response to incremental cycling.

Exercise ventilatory kinematics in endurance trained and untrained men and women

To determine how increased ventilatory demand impacts ventilatory kinematics, we compared the total chest wall volume variations (V(CW)) of male and female endurance-trained athletes (ET) to untrained individuals (UT) during exercise. We hypothesized that training and gender would have an effect on V(CW) and kinematics at maximal exercise. Gender and training significantly influenced chest wall kinematics. Female ET did not change chest wall end-expiratory volume (V(CW,ee)) or pulmonary ribcage (V(RCp,ee)) with exercise, while female UT significantly decreased V(CW,ee) and V(RCp,ee) with exercise (p<0.05). Female ET significantly increased pulmonary ribcage end-inspiratory volume (V(RCp,ei)) with exercise (p<0.05), while female UT did not change V(RCp,ei) with exercise. Male ET significantly increased V(RCp,ei) with exercise (p<0.05); male UT did not. Men and women had significantly different variation of V(CW) (p<0.05). Women demonstrated the greatest variation of V(CW) in the pulmonary ribcage compartment (V(RCp)). Men had even volumes variation of the V(RCp) and the abdomen (V(Ab)). In conclusion, gender and training had a significant impact on ventilatory kinematics.

An examination of exercise mode on ventilatory patterns during incremental exercise

Both cycle ergometry and treadmill exercise are commonly employed to examine the cardiopulmonary system under conditions of precisely controlled metabolic stress. Although both forms of exercise are effective in elucidating a maximal stress response, it is unclear whether breathing strategies or ventilator efficiency differences exist between exercise modes. The present study examines breathing strategies, ventilatory efficiency and ventilatory capacity during both incremental cycling and treadmill exercise to volitional exhaustion. Subjects (n = 9) underwent standard spirometric assessment followed by maximal cardiopulmonary exercise testing utilising cycle ergometry and treadmill exercise using a randomised cross-over design. Respiratory gases and volumes were recorded continuously using an online gas analysis system. Cycling exercise utilised a greater portion of ventilatory capacity and higher tidal volume at comparable levels of ventilation. In addition, there was an increased mean inspiratory flow rate at all levels of ventilation during cycle exercise, in the absence of any difference in inspiratory timing. Exercising V(E)/VCO₂slope and the lowest V(E)/VCO₂value, was lower during cycling exercise than during the treadmill protocol indicating greater ventilatory efficiency. The present study identifies differing breathing strategies employed during cycling and treadmill exercise in young, trained individuals. Exercise mode should be accounted for when assessing breathing patterns and/or ventilatory efficiency during incremental exercise.

Assessment of physiological capacities of elite athletes & respiratory limitations to exercise performance

Physiological assessment of athletes is an important process for the characterization of the athlete, monitoring progress and the trained state or 'level of preparedness' of an athlete, as well as aiding the process of training program design. Interestingly, the majority of physiological assessments performed on athletes can also be performed on children with disease, and therefore clinicians can learn a great deal about physiology and assessment of patient populations through the examination of the physiological responses of elite athletes. This review describes typical physiological responses of elite athletes to tests of aerobic and anaerobic metabolism and provides a specific focus upon respiratory limitations to exercise performance. Typical responses of elite athletes are described to provide the scientist and clinician with a perspective of the upper range of physiological capacities of elite athletes.

Ventilatory capacity and its utilisation during exercise

Inadequate ventilation is not usually considered an exercise-limiting factor because it is thought that the respiratory system's maximum ventilatory capacity is never reached during exercise. This so-called reserve can be defined as the difference between the ventilated volume, attained during a maximum voluntary ventilation manoeuvre (MVV) and the maximum ventilation V(Emax) achieved during exercise. This study explores the relationship between ventilatory capacity, the MVV manoeuvre, and respiratory function. Twelve healthy adults completed a maximal cycle test and 12-, 30-, and 60-s MVV manoeuvres while seated or standing. The MVV(12) manoeuvre produced the largest ventilation volume (115 +/- 22 vs. (V(Emax)) 102 +/- 23 L min(-1)), signifying a reserve of 13%. With longer MVV (30 and 60 s) manoeuvres, the ventilated volume and (V(Emax)) were the same, signifying no reserve. MVV increased with the forced expiratory volume at one second, FEV(1). The breath rates were approximately 120 vs. 48 +/- 6 breaths min(-1) and tidal volumes were approximately 1 vs. 2.2 +/- 0.5 L during the MVV and exercise, respectively. The longer MVV manoeuvre provides the best estimate of ventilatory capacity and shows that 100% of the reserve is used during maximal exercise. A nomogram relating MVV to FEV(1) is shown.

The respiratory time and flow profile at volitional exercise termination

In this study, we examine the effect of exercise on the time and flow characteristics of the respiratory cycle profile at the point of volitional exercise termination. Eight males (mean age 29 years, s = 10; body mass 74 kg, s = 7; height 1.75 m, s = 0.04) undertook a cycle test to volitional exhaustion on a cycle ergometer, which allowed peak oxygen uptake (VO(2peak)) to be measured (mean 51 ml x kg(-1) x min(-1), s = 7). At a later date, two sub-maximal tests to volitional exhaustion were completed in a random order at 76% (s = 6) and 86% VO(2peak) (s = 7). As expected, the magnitude of the respiratory flow and time characteristics varied with the three exercise intensities, as did the point of exercise termination and terminal ventilation rates, which varied from 7 to 27 min and 112 to 132 litres x min(-1) respectively. More importantly, however, at exercise termination some of the characteristics were similar, particularly the breathing frequency (at termination 49 breaths x min(-1)), the ratio between inspiration and total breath time (0.5), and the later occurrence of peak inspiratory flow (0.24-0.48 s). The coincident unity of these time and flow profile characteristics at exercise termination illustrates how the integration of timing and flow during breathing influence exercise capacity in non-elite athletes.

Inspiratory flow rates during hard work when breathing through different respirator inhalation and exhalation resistances

There has been a long-standing debate regarding the adequacy of airflow rates used in respirator certification testing and whether these test flow rates underestimate actual values. This study investigated breath by breath inspiratory peak flow rate, minute ventilation, and instantaneous flow rates of eight young, healthy volunteers walking on a treadmill at 80-85% of maximal aerobic capacity until exhaustion while wearing an air-purifying respirator with one of eight combinations of inhalation and exhalation resistance. An analysis of variance was performed to identify differences among the eight conditions. Scheffe's post hoc analysis indicated which means differed. The group of conditions with the highest average value for each parameter was identified and considered to represent a worst-case scenario. Data was reported for these conditions. A Gaussian distribution was fit to the data and the 99.9% probability levels determined. The 99.9% probability level for the peak and instantaneous flow rates were 374 L/min and 336 L/min, respectively. The minute ventilation distribution was not Gaussian. Less than 1% of the recorded minute ventilations exceeded 135 L/min. Instantaneous flow rates exceeded the National Institute for Occupational Safety and Health's respirator test standards of 64, 85, and 100 L/min constant flow 91%, 87%, and 82% of the time, respectively. The recorded minute ventilations exceeded the 40 L/min minute ventilation test standard (for tests with a sinusoidal flow pattern) 100% of the time. This study showed that young, healthy respirator wearers generated peak flow rates, minute ventilations, and instantaneous flow rates that consistently exceeded current test standards. Their flow rates should be higher than those of a respirator wearer performing occupational work and could be considered upper limits. Testing respirators and respirator cartridges using a sinusoidal breathing pattern with a minute ventilation of 135 L/min (peak flow rate approximately 424 L/min) would encompass 99% of the recorded minute ventilations and 99.9% of the predicted peak and instantaneous flow rates from this study and would more accurately reflect human respiration during strenuous exercise.

[Response of tidal volume to inspiratory time ratio during incremental exercise]

OBJECTIVE

There is some debate about the participation of the Hering-Breuer reflex during exercise in human beings. This study aimed to investigate breathing pattern response during an incremental exercise test with a cycle ergometer. Participation of the Hering-Breuer reflex in the control of breathing was to be indirectly investigated by analyzing the ratio of tidal volume (VT) to inspiratory time (tI).

SUBJECTS AND METHODS

The 9 active subjects who participated the study followed an incremental protocol on a cycle ergometer until peak criteria were reached. During exercise, VT/ti can be described in 2 phases, separated by activation of the Hering-Breuer reflex (inspiratory off-switch threshold). In phase 1, ventilation increases because VT increases, resulting in a slight decrease in tI, whereas, in phase 2, increased ventilation is due to both an increase in VT and a decrease in tI.

RESULTS

The mean (SD) inspiratory off-switch threshold was 84.6% (6.3%) when expressed relative to peak VT (mean, 3065 [566.8] mL) and 48% (7.2%) relative to the forced vital capacity measured by resting spirometry. The inspiratory off-switch threshold correlated positively (r=0.93) with the second ventilatory threshold, or respiratory compensation point.

CONCLUSIONS

The inspiratory off-switch threshold and VT/ti are directly related to one another. The inspiratory off-switch threshold was related to the second ventilatory threshold, suggesting that the Hering-Breuer reflex participates in control of the breathing pattern during exercise. Activation of the reflex could contribute by signaling the respiratory centers to change the breathing pattern.

A nomogram for assessment of breathing patterns during treadmill exercise

OBJECTIVE

To assess the breathing patterns of trained athletes under different conditions. The hypothesis is that the breathing pattern during a progressive treadmill exercise is independent of the protocol, at least in healthy people, and can be assessed using a nomogram.

METHODS

A total of 43 male and 21 female athletes from different sports were studied. They performed one of two different protocols (steps or ramp) on a treadmill. The two protocols started at the same speed and had the same rate of increase in work. During the test, the expired air was analysed for CO2 and O2. Ventilation (VE) was continuously recorded, and tidal volume (Vt) and breathing frequency (BF) at the same intensity were analysed for both protocols, as well as Vt/T(i) and T(i)/T(tot).

RESULTS

No significant differences were observed in Vt and BF between the two protocols in either the men or women at any level (confidence intervals up to 0.958 in all the groups). T(i)/T(tot) remained constant, and all increases in VE were strongly related to the respective increases in Vt/T(i). Plots of data for men and women showed a curvilinear relation between Vt and BF which could be fitted with an exponential function with a strong correlation (R2 = 0.98 for men and 0.97 for women).

CONCLUSIONS

Graphic expression of Vt v BF is a useful nomogram for the routine assessment of ventilatory response during exercise in healthy trained subjects.

Relation between physical exertion and heart rate variability characteristics in professional cyclists during the Tour of Spain

BACKGROUND

Continued exposure to prolonged periods of intense exercise may unfavourably alter neuroendocrine, neuromuscular, and cardiovascular function.

OBJECTIVE

To examine the relation between quantifiable levels of exertion (TRIMPS) and resting heart rate (HR) and resting supine heart rate variability (HRV) in professional cyclists during a three week stage race.

METHOD

Eight professional male cyclists (mean (SEM) age 27 (1) years, body mass 65.5 (2.3) kg, and maximum rate of oxygen consumption (VO(2)max) 75.6 (2.2) ml/kg/min) riding in the 2001 Vuelta a España were examined for resting HR and HRV on the mornings of day 0 (baseline), day 10 (first rest day), and day 17 (second rest day). The rest days followed stages 1-9 and 10-15 respectively. HR was recorded during each race stage, and total HR time was categorised into a modified, three phase TRIMPS schema. These phases were based on standardised physiological laboratory values obtained during previous VO(2)max testing, where HR time in each phase (phase I = light intensity and less than ventilatory threshold (VT; approximately 70% VO(2)max); phase II = moderate intensity between VT and respiratory compensation point (RCP; approximately 90% VO(2)max); phase III = high intensity (>RCP)) was multiplied by exertional factors of 1, 2, and 3 respectively.

RESULTS

Multivariate analysis of variance showed that total TRIMPS for race stages 1-9 (2466 (90)) were greater than for stages 10-15 (2055 (65)) (p<0.0002). However, TRIMPS/day were less for stages 1-9 (274 (10)) than for stages 10-15 (343 (11)) (p<0.01). Despite a trend to decline, no difference in supine resting HR was found between day 0 (53.2 (1.8) beats/min), day 10 (49.0 (2.8) beats/min), and day 17 (48.0 (2.6) beats/min) (p = 0.21). Whereas no significant group mean changes in HR or HRV indices were noted during the course of the race, significant inverse Pearson product-moment correlations were observed between all HRV indices relative to total TRIMPS and TRIMPS/day accumulated in race stages 10-15. Total TRIMPS correlated with square root of mean squared differences of successive RR intervals (r = -0.93; p<0.001), standard deviation of the RR intervals (r = -0.94; p<0.001), log normalised total power (r = -0.97; p<0.001), log normalised low frequency power (r = -0.79; p<0.02), and log normalised high frequency power (r = -0.94; p<0.001).

CONCLUSION

HRV may be strongly affected by chronic exposure to heavy exertion. Training volume and intensity are necessary to delineate the degree of these alterations.

The Science of Cycling

The aim of this review is to provide greater insight and understanding regarding the scientific nature of cycling. Research findings are presented in a practical manner for their direct application to cycling. The two parts of this review provide information that is useful to athletes, coaches and exercise scientists in the prescription of training regimens, adoption of exercise protocols and creation of research designs. Here for the first time, we present rationale to dispute prevailing myths linked to erroneous concepts and terminology surrounding the sport of cycling. In some studies, a review of the cycling literature revealed incomplete characterisation of athletic performance, lack of appropriate controls and small subject numbers, thereby complicating the understanding of the cycling research. Moreover, a mixture of cycling testing equipment coupled with a multitude of exercise protocols stresses the reliability and validity of the findings. Our scrutiny of the literature revealed key cycling performance-determining variables and their training-induced metabolic responses. The review of training strategies provides guidelines that will assist in the design of aerobic and anaerobic training protocols. Paradoxically, while maximal oxygen uptake (V-O(2max)) is generally not considered a valid indicator of cycling performance when it is coupled with other markers of exercise performance (e.g. blood lactate, power output, metabolic thresholds and efficiency/economy), it is found to gain predictive credibility. The positive facets of lactate metabolism dispel the 'lactic acid myth'. Lactate is shown to lower hydrogen ion concentrations rather than raise them, thereby retarding acidosis. Every aspect of lactate production is shown to be advantageous to cycling performance. To minimise the effects of muscle fatigue, the efficacy of employing a combination of different high cycling cadences is evident. The subconscious fatigue avoidance mechanism 'teleoanticipation' system serves to set the tolerable upper limits of competitive effort in order to assure the athlete completion of the physical challenge. Physiological markers found to be predictive of cycling performance include: (i) power output at the lactate threshold (LT2); (ii) peak power output (W(peak)) indicating a power/weight ratio of > or =5.5 W/kg; (iii) the percentage of type I fibres in the vastus lateralis; (iv) maximal lactate steady-state, representing the highest exercise intensity at which blood lactate concentration remains stable; (v) W(peak) at LT2; and (vi) W(peak) during a maximal cycling test. Furthermore, the unique breathing pattern, characterised by a lack of tachypnoeic shift, found in professional cyclists may enhance the efficiency and metabolic cost of breathing. The training impulse is useful to characterise exercise intensity and load during training and competition. It serves to enable the cyclist or coach to evaluate the effects of training strategies and may well serve to predict the cyclist's performance. Findings indicate that peripheral adaptations in working muscles play a more important role for enhanced submaximal cycling capacity than central adaptations. Clearly, relatively brief but intense sprint training can enhance both glycolytic and oxidative enzyme activity, maximum short-term power output and V-O(2max). To that end, it is suggested to replace approximately 15% of normal training with one of the interval exercise protocols. Tapering, through reduction in duration of training sessions or the frequency of sessions per week while maintaining intensity, is extremely effective for improvement of cycling time-trial performance. Overuse and over-training disabilities common to the competitive cyclist, if untreated, can lead to delayed recovery.

Science and cycling: current knowledge and future directions for research

In this holistic review of cycling science, the objectives are: (1) to identify the various human and environmental factors that influence cycling power output and velocity; (2) to discuss, with the aid of a schematic model, the often complex interrelationships between these factors; and (3) to suggest future directions for research to help clarify how cycling performance can be optimized, given different race disciplines, environments and riders. Most successful cyclists, irrespective of the race discipline, have a high maximal aerobic power output measured from an incremental test, and an ability to work at relatively high power outputs for long periods. The relationship between these characteristics and inherent physiological factors such as muscle capilliarization and muscle fibre type is complicated by inter-individual differences in selecting cadence for different race conditions. More research is needed on high-class professional riders, since they probably represent the pinnacle of natural selection for, and physiological adaptation to, endurance exercise. Recent advances in mathematical modelling and bicycle-mounted strain gauges, which can measure power directly in races, are starting to help unravel the interrelationships between the various resistive forces on the bicycle (e.g. air and rolling resistance, gravity). Interventions on rider position to optimize aerodynamics should also consider the impact on power output of the rider. All-terrain bicycle (ATB) racing is a neglected discipline in terms of the characterization of power outputs in race conditions and the modelling of the effects of the different design of bicycle frame and components on the magnitude of resistive forces. A direct application of mathematical models of cycling velocity has been in identifying optimal pacing strategies for different race conditions. Such data should, nevertheless, be considered alongside physiological optimization of power output in a race. An even distribution of power output is both physiologically and biophysically optimal for longer ( > 4 km) time-trials held in conditions of unvarying wind and gradient. For shorter races (e.g. a 1 km time-trial), an 'all out' effort from the start is advised to 'save' time during the initial phase that contributes most to total race time and to optimize the contribution of kinetic energy to race velocity. From a biophysical standpoint, the optimum pacing strategy for road time-trials may involve increasing power in headwinds and uphill sections and decreasing power in tailwinds and when travelling downhill. More research, using models and direct power measurement, is needed to elucidate fully how much such a pacing strategy might save time in a real race and how much a variable power output can be tolerated by a rider. The cyclist's diet is a multifactorial issue in itself and many researchers have tried to examine aspects of cycling nutrition (e.g. timing, amount, composition) in isolation. Only recently have researchers attempted to analyse interrelationships between dietary factors (e.g. the link between pre-race and in-race dietary effects on performance). The thermal environment is a mediating factor in choice of diet, since there may be competing interests of replacing lost fluid and depleted glycogen during and after a race. Given the prevalence of stage racing in professional cycling, more research into the influence of nutrition on repeated bouts of exercise performance and training is required.

Kinetics of VO(2) in professional cyclists

PURPOSE

To analyze the kinetics of oxygen uptake (VO(2)) in professional road cyclists during a ramp cycle ergometer test and to compare the results with those derived from well-trained amateur cyclists.

METHODS

Twelve professional cyclists (P group; 25 +/- 1 yr; maximal power output (W(max)), 508.3 +/- 9.3 watts) and 10 amateur cyclists (A group; 22 +/- 1 y; W(max), 429.9 +/- 8.6 watts) performed a ramp test until exhaustion (power output increases of 25 watts x min(-1)). The regression lines of the VO(2):power output (W) relationship were calculated for the following three phases: phase I (below the lactate threshold (LT)), phase II (between LT and the respiratory compensation point (RCP)), and phase III (above RCP).

RESULTS

In group P, the mean slope (Delta VO(2):Delta W) of the VO(2):W relationship decreased significantly (P < 0.01) across the three phases (9.9 +/- 0.1, 8.9 +/- 0.2, and 3.8 +/- 0.6 mL O(2) x watts(-1) x min(-1) for phases I, II, and III, respectively). No significant differences (P > 0.05) were found between phases I and II (P > 0.05) in group A, whereas Delta VO(2):Delta W significantly increased in phase III (P < 0.01), compared with phase II (10.2 +/- 0.3, 9.2 +/- 0.4, and 10.1 +/- 1.1 mL O(2) x watts(-1) x min(-1) in phases I, II, and III, respectively). The mean value of Delta VO(2):Delta W for phase III was significantly lower in group P than in group A (P < 0.01).

CONCLUSION

Contrary to the case in amateur riders, the rise in VO(2) in professional cyclists is attenuated at moderate to high workloads. This is possibly an adaptation to the higher demands of their training/competition schedule.

Physiology of professional road cycling

Professional road cycling is an extreme endurance sport. Approximately 30000 to 35000 km are cycled each year in training and competition and some races, such as the Tour de France last 21 days (approximately 100 hours of competition) during which professional cyclists (PC) must cover >3500 km. In some phases of such a demanding sport, on the other hand, exercise intensity is surprisingly high, since PC must complete prolonged periods of exercise (i.e. time trials, high mountain ascents) at high percentages (approximately 90%) of maximal oxygen uptake (VO2max) [above the anaerobic threshold (AT)]. Although numerous studies have analysed the physiological responses of elite, amateur level road cyclists during the last 2 decades, their findings might not be directly extrapolated to professional cycling. Several studies have recently shown that PC exhibit some remarkable physiological responses and adaptations such as: an efficient respiratory system (i.e. lack of 'tachypnoeic shift' at high exercise intensities); a considerable reliance on fat metabolism even at high power outputs; or several neuromuscular adaptations (i.e. a great resistance to fatigue of slow motor units). This article extensively reviews the different responses and adaptations (cardiopulmonary system, metabolism, neuromuscular factors or endocrine system) to this sport. A special emphasis is placed on the evaluation of performance both in the laboratory (i.e. the controversial Conconi test, distinction between climbing and time trial ability, etc.) and during actual competitions such as the Tour de France.

Preferred pedalling cadence in professional cycling

PURPOSE

The aim of this investigation was to evaluate the preferred cycling cadence of professional riders during competition.

METHODS

We measured the cadence of seven professional cyclists (28 +/- 1 yr) during 3-wk road races (Giro d'Italia, Tour de France, and Vuelta a España) involving three main competition requirements: uphill cycling (high mountain passes of approximately 15 km, or HM); individual time trials of approximately 50 km on level ground (TT); and flat, long ( approximately 190 km) group stages (F). Heart rate (HR) data were also recorded as an indicator of exercise intensity during HM, TT, and F.

RESULTS

Mean cadence was significantly lower (P < 0.01) during HM (71.0 +/- 1.4 rpm) than either F and TT (89.3 +/- 1.0 and 92.4 +/- 1.3 rpm, respectively). HR was similar during HM and TT (157 +/- 4 and 158 +/- 3 bpm) and in both cases higher (P < 0.01) than during F (124 +/- 2 bpm).

CONCLUSION

During both F and TT, professional riders spontaneously adopt higher cadences (around 90 rpm) than those previously reported in the majority of laboratory studies as being the most economical. In contrast, during HM they seem to adopt a more economical pedalling rate (approximately 70 rpm), possibly as a result of the specific demands of this competition phase.

Effects of endurance training on the breathing pattern of professional cyclists

The aim of this longitudinal study was to clarify the changes induced by endurance training on the breathing pattern of 13 professional cyclists (age+/-SD: 24+/-2 years; VO(2 max) approximately 75 ml x kg(-1) x min(-1)) during the three periods (rest, precompetition, and competition) of a sports season. Both the volume and the intensity of training were quantified during these periods. In each session (corresponding to each of the three periods) all subjects performed (1) a pulmonary function test (to measure forced vital capacity [FVC], peak expiratory flow [PEF], and maximal voluntary ventilation [MVV]), and (2) a ramp test until exhaustion on a cycle ergometer (workload increases of 25 W x min(-1)). The following variables were recorded every 100 W until the end of the tests: pulmonary ventilation (VE, in l x min(-1) BTPS), tidal volume (VT, inl BTPS), breathing frequency (f(b), in breaths x min(-1)), ventilatory equivalents for oxygen (VE x VO(2)(-1)) and carbon dioxide (VE x VCO(2)(-1)), inspiratory (TI) and expiratory (TE) times (s), ratio of TI to total respiratory duration or inspiratory "duty cycle" (TI/TTOT, and mean inspiratory flow rate (VT)/TI), in l x s(-1)). The results showed no changes in any of these variables (p>0.05) between the three periods of study, despite significant changes in training loads (i.e., increases in the volume and/or intensity of training throughout the season). These findings suggest that endurance conditioning does not alter the breathing pattern of professional cyclists during an incremental exercise test.

Effects of endurance training on the isocapnic buffering and hypocapnic hyperventilation phases in professional cyclists

OBJECTIVES

To evaluate the changes produced in both the isocapnic buffering and hypocapnic hyperventilation (HHV) phases of professional cyclists (n = 11) in response to endurance training, and to compare the results with those of amateur cyclists (n = 11).

METHODS

Each professional cyclist performed three laboratory exercise tests to exhaustion during the active rest (autumn: November), precompetition (winter: January), and competition (spring: May) periods of the sports season. Amateur cyclists only performed one exercise test during the competition period. The isocapnic buffering and HHV ranges were calculated during each test and defined as Vo2 and power output (W).

RESULTS

No significant differences were found in the isocapnic buffering range in each of the periods of the sports season in professional cyclists. In contrast, there was a significant reduction in the HHV range (expressed in W) during both the competition (p<0.01) and precompetition(p<0.05) periods compared with the rest period. On the other hand, a longer HHV range (p<0.01) was observed in amateur cyclists than in professional cyclists (whether this was expressed in terms of Vo2 or W).

CONCLUSIONS

No change is observed in the isocapnic buffering range of professional cyclists throughout a sports season despite a considerable increase in training loads and a significant reduction in HHV range expressed in terms of power output.

The slow component of VO2 in professional cyclists

OBJECTIVES

To analyse the slow component of oxygen uptake (VO2) in professional cyclists and to determine whether this phenomenon is due to altered neuromuscular activity, as assessed by surface electromyography (EMG).

METHODS

The following variables were measured during 20 minute cycle ergometer tests performed at about 80% of VO2MAX in nine professional road cyclists (mean (SD) age 26 (2) years; VO2max 72.6 (2.2) ml/kg/min): heart rate (HR), gas exchange variables (VO2, ventilation (VE), tidal volume (VT), breathing frequency (fb), ventilatory equivalents for oxygen and carbon dioxide (VE/VO2 and VE/VCO2 respectively), respiratory exchange ratio (RER), and end tidal PO2 and PCO2 (PETO2 and PETCO2 respectively)), blood variables (lactate, pH, and [HCO3-]) and EMG data (root mean from square voltage (rms-EMG) and mean power frequency (MPF)) from the vastus lateralis muscle.

RESULTS

The mean magnitude of the slow component (from the end of the third minute to the end of exercise) was 130 (0.04) ml in 17 minutes or 7.6 ml/min. Significant increases from three minute to end of exercise values were found for the following variables: VO2 (p<0.01), HR (p<0.01), VE (p<0.05), fb (p<0.01), VE/VO2 (p<0.05), VE/VCO2 (p<0.01), PETO2 (p<0.05), and blood lactate (p<0.05). In contrast, rms-EMG and MPF showed no change (p>0.05) throughout the exercise tests.

CONCLUSIONS

A significant but small VO2 slow component was shown in professional cyclists during constant load heavy exercise. The results suggest that the primary origin of the slow component is not neuromuscular factors in these subjects, at least for exercise intensities up to 80% of VO2MAX.

Heart rate and performance parameters in elite cyclists: a longitudinal study

PURPOSE

This study was designed to evaluate the stability of target heart rate (HR) values corresponding to performance markers such as lactate threshold (LT) and the first and second ventilatory thresholds (VT1, VT2) in a group of 13 professional road cyclists (VO2max, approximately 75.0 mL x kg(-1) x min(-1)) during the course of a complete sports season.

METHODS

Each subject performed a progressive exercise test on a bicycle ergometer (ramp protocol with workload increases of 25 W x min(-1)) three times during the season corresponding to the "active" rest (fall: November), precompetition (winter: January), and competition periods (spring: May) to determine HR values at LT, VT1 and VT2.

RESULTS

Despite a significant improvement in performance throughout the training season (i.e., increases in the power output eliciting LT, VT1, or VT2), target HR values were overall stable (HR at LT: 154 +/- 3, 152 +/- 3, and 154 +/- 2 beats x min(-1); HR at VT1: 155 +/- 3, 156 +/- 3, and 159 +/- 3 beats x min(-1); and at VT2: 178 +/- 2, 173 +/- 3, and 176 +/- 2 beats x min(-1) during rest, precompetition, and competition periods, respectively).

CONCLUSION

A single laboratory testing session at the beginning of the season might be sufficient to adequately prescribe training loads based on HR data in elite endurance athletes such as professional cyclists. This would simplify the testing schedule generally used for this type of athlete.

Metabolic and neuromuscular adaptations to endurance training in professional cyclists: a longitudinal study

The aim of this longitudinal study was to analyze the changes in several metabolic and neuromuscular variables in response to endurance training during three defined periods of a full sports season (rest, precompetition and competition). The study population was formed by thirteen professional cyclists (age +/- SEM: 24+/-1 years; mean V(O2 max) approximately 74 ml kg(-1) min(-1)). In each testing session, subjects performed a ramp test until exhaustion on a cycle ergometer (workload increases of 25 W min(-1)). The following variables were recorded every 100 W until the tests: oxygen consumption (V(O2) in l min(-1)), respiratory exchange ratio (RER in V(CO2) V(O2)(-1)) and blood lactate, pH and bicarbonate concentration [HCO3(-)]. Surface electromyography (EMG) recordings were also obtained from the vastus lateralis to determine the variables: root mean square voltage (rms-EMG) and mean power frequency (MPF). RER and lactate values both showed a decrease (p<0.05) throughout the season at exercise intensities corresponding to submaximal workloads. In contrast, no significant differences were found in mean pH or [HCO(3-)]. Finally, rms-EMG tended to increase during the season, with significant differences (p<0.05) observed mainly between the competition and rest periods at most workloads. In contrast, precompetition MPF values increased (p<0.05) with respect to resting values at most submaximal workloads but fell (p<0.05) during the competition period. Our findings suggest that endurance conditioning induces the following general adaptations in elite athletes: (1) lower circulating lactate and increased reliance on aerobic metabolism at a given submaximal intensity, and possibly (2) an enhanced recruitment of motor units in active muscles, as suggested by rms-EMG data.