Respiratory Compensation Threshold Research Articles

Reliability of the talk test as a surrogate of ventilatory and respiratory compensation thresholds.

Reliability of the talk test as a surrogate of ventilatory and respiratory compensation thresholds.

Relationship Between the Talk Test and Ventilatory Thresholds in Well-Trained Cyclists

The aim of this study was to extend the range of populations where the Talk Test (TT) might be used as a marker of physiologic thresholds. Eighteen highly trained cyclists underwent 2 incremental tests. One test included measurement of respiratory gas exchange to determine the ventilatory (VT) and respiratory compensation thresholds (RCTs). On a separate day, a TT was performed using the same exercise protocol. During TT, subjects read a standard paragraph at the end of each stage. The first stage at which the cyclists could not talk comfortably and could definitely not talk were referred to as the equivocal (EQ) and the negative stages (NEG), respectively. There were no significant differences in workload, heart rate, lactate, and rating of perceived exertion between VT (3.7 ± 0.4 W kg, 150 ± 10 b min, 1.6 ± 0.3 mm L, and 4.1 ± 1.4, respectively) vs. EQ (3.6 ± 0.4 W kg, 148 ± 12 b min, 1.3 ± 0.5 mm L, and 3.8 ± 1.2, respectively) and RCT (5.3 ± 0.4 W kg, 177 ± 7 b min, 4.0 ± 0.9 mm L, and 7.2 ± 1.0, respectively) vs. NEG (5.3 ± 0.5 W kg, 176 ± 10 b min, 4.2 ± 1.3 mm L, and 6.8 ± 1.5, respectively). We found significant relationships (p < 0.01) between VT and EQ and RCT and NEG for workload (r = 0.86 and 0.94, respectively), heart rate (r = 0.79 and 0.92, respectively), and rating of perceived exertion (r = 0.79 and 0.88, respectively). In conclusion, the present study showed that the EQ and NEG stages of TT can be used as a simple and practical surrogate of the VT and RCT in highly trained cyclists.

Does Polarized Training Improve Performance in Recreational Runners?

To quantify the impact of training-intensity distribution on 10K performance in recreational athletes. 30 endurance runners were randomly assigned to a training program emphasizing low-intensity, sub-ventilatory-threshold (VT), polarized endurance-training distribution (PET) or a moderately high-intensity (between-thresholds) endurance-training program (BThET). Before the study, the subjects performed a maximal exercise test to determine VT and respiratory-compensation threshold (RCT), which allowed training to be controlled based on heart rate during each training session over the 10-wk intervention period. Subjects performed a 10-km race on the same course before and after the intervention period. Training was quantified based on the cumulative time spent in 3 intensity zones: zone 1 (low intensity, <VT), zone 2 (moderate intensity, between VT and RCT), and zone 3 (high intensity, >RCT). The contribution of total training time in each zone was controlled to have more low-intensity training in PET (±77/3/20), whereas for BThET the distribution was higher in zone 2 and lower in zone 1 (±46/35/19). Both groups significantly improved their 10K time (39min18s ± 4min54s vs 37min19s ± 4min42s, P < .0001 for PET; 39min24s ± 3min54s vs 38min0s ± 4min24s, P < .001 for BThET). Improvements were 5.0% vs 3.6%, ~41 s difference at post-training-intervention. This difference was not significant. However, a subset analysis comparing the 12 runners who actually performed the most PET (n = 6) and BThET (n = 16) distributions showed greater improvement in PET by 1.29 standardized Cohen effect-size units (90% CI 0.31-2.27, P = .038). Polarized training can stimulate greater training effects than between-thresholds training in recreational runners.

Neuromuscular adaptations during combined strength and endurance training in endurance runners: maximal versus explosive strength training or a mix of both

This study compared the effects of mixed maximal strength and explosive strength training with maximal strength training and explosive strength training combined with endurance training over an 8-week training intervention. Male subjects (age 21-45years) were divided into three strength training groups, maximal (MAX, n=11), explosive (EXP, 10) and mixed maximal and explosive (MIX, 9), and a circuit training control group, (CON, 7). Strength training one to two times a week was performed concurrently with endurance training three to four times a week. Significant increases in maximal dynamic strength (1RM), countermovement jump (CMJ), maximal muscle activation during 1RM in MAX and during CMJ in EXP, peak running speed (S (peak)) and running speed at respiratory compensation threshold (RCT(speed)) were observed in MAX, EXP and MIX. Maximal isometric strength and muscle activation, rate of force development (RFD), maximal oxygen uptake [Formula: see text] and running economy (RE) at 10 and 12kmhr(-1) did not change significantly. No significant changes were observed in CON in maximal isometric strength, RFD, CMJ or muscle activation, and a significant decrease in 1RM was observed in the final 4weeks of training. RE in CON did not change significantly, but significant increases were observed in S (peak), RCT(speed) and [Formula: see text] Low volume MAX, EXP and MIX strength training combined with higher volume endurance training over an 8-week intervention produced significant gains in strength, power and endurance performance measures of S (peak) and RCT(speed), but no significant changes were observed between groups.

Application of near Infrared Spectroscopy in Evaluating Cerebral and Muscle Haemodynamics during Exercise and Sport

Near infrared (NIR) spectroscopy is a non-invasive optical technique that has been used to evaluate cerebral and muscle haemodynamic responses during exercise in situ. Its ease of use, portability, relatively low cost, along with the capability of evaluating cardiorespiratory responses simultaneously, has made it a useful technique to study exercise performance in a more holistic manner. The evidence indicates that there are systematic changes in the muscle and cerebral haemodynamic responses which are coincident with the respiratory gas exchange alterations occurring at the lactate and respiratory compensation thresholds during incremental exercise. During the Wingate (anaerobic) test, the peak oxygen uptake and degree of muscle deoxygenation is comparable to that attained during maximal incremental exercise, implying that there is a large aerobic component during a short duration of intense anaerobic exercise. Studies that have measured cerebral and muscle NIR spectroscopy simultaneously during dynamic whole body exercise support the hypotheses that at exercise intensities above the respiratory compensation threshold: (i) the accessory respiratory muscles compromise oxygen availability to the muscles directly involved in exercise, thereby contributing to fatigue and (ii) there is a systematic decline in cerebral oxygenation until exercise is terminated, thereby supporting the possibility of a supraspinal component to fatigue. Research pertaining to the application of NIR spectroscopy on cerebral and muscle haemodynamics under hypoxic conditions has indicated that the reductions in maximal exercise and aerobic capacity cannot be explained solely on the basis of these acute changes. Additionally, the improvements in maximal and submaximal exercise performance subsequent to endurance, interval and simulated hypoxic training programmes can occur independently of any alterations in cerebral and muscle haemodynamics. Wireless NIR spectroscopy is a useful technique to evaluate sport performance in the field setting and will evolve as an important method for designing and implementing training methods for this purpose.

Physical and thermal strain of firefighters according to the firefighting tactics used to suppress wildfires

The aim of this study was to analyse the physiological strain of firefighters, using heart rate (HR) and core temperature, during real wildfire suppression according to the type of attack performed (direct, indirect or mixed). Threeintensity zones were established according to the HR corresponding to the ventilatory threshold (VT) and respiratory compensation threshold (RCT): zone 1, <VT; zone 2 (Z2), between VT and RCT; zone 3 (Z3), >RCT. The exercise workload (training impulse (TRIMP)), the physiological strain index (PSI) and the cumulative heat strain index(CHSI) were calculated using the time spent in each zone, and the HR and core temperature, respectively. Significantly higher mean HR, time spent in Z2 and Z3 and TRIMP h−1 were found in direct and mixed versus indirect attacks. The highest PSI and CHSI were observed in the direct attack. In conclusion, exercise strain and combined thermal strain, but not core temperature during wildfire suppression, are related to the type of attack performed. Statement of relevance: Our findings demonstrated that wildfire firefighting is associated with high physiological demands, which vary significantly depending on the tactics chosen for performing the task. These results should be kept in mind when planning programmes to improve wildland firefighters' physical fitness, which will allow improvement in their performance.

Physiology of Ski Mountaineering Racing

The aim of this study was to quantify and describe the exercise intensity of ski mountaineering racing, and to identify the best physiological predictors of ski mountaineering racing. Before participating in the race in which heart rate (HR) and speed were continuously recorded, 10 trained ski-mountaineers performed a field maximal test to determine the first ventilatory threshold (VT1) and the respiratory compensation threshold (RCT) in order to establish 3 exercise intensity zones (Z1: below VT1, Z2: between VT1 and RCT, and Z3: above RCT). Energy cost (EC) of each subject was estimated on the HR/ V˙O2 relationship obtained during the field maximal test. VT1 and RCT threshold were equal to 84.2±3.0 and 94.5±1.7% of HR (max). Race time was significantly correlated with V˙O2max (r = -0.87), VT1 (r = -0.82) and RCT (r = -0.85) expressed for body mass unit. The mean race time and the mean HR were 101±11 min and 93.4±1.8% of HR (max). The % race time spent in Z1, Z2 and Z3, were 7.0±4.8, 51.3±4.7 and 42.0±6.5%, respectively. The mean value of EC during the two uphill of the race was 14.3±2.6 J x kg(-1) x m(-1). HR and speed decreased significantly during the second uphill whereas EC increased significantly by ∼15%. Data obtained in the present study represent the first qualitative description of physiology demand of ski mountaineering racing. The long period of time spent just below and above RCT suggest that ski-mountaineering can be viewed as one of the most strenuous endurance sports like cross-country skiing, running and off-road biking. In addition to high aerobic capacities, body mass seems to appear as a key factor given that performance in ski mountaineering is strongly correlated to relative common physiological variables. The changes of HR, speed and EC during the second uphill, which indicate the prevalence of fatigue, confirm the exhaustive character of ski mountaineering.

Exercise Intensity and Load During Different Races in Youth and Junior Cyclists

This study analyzed and compared the exercise intensity exerted by Youth and Junior cyclists in single-day and stage races. Heart rate was measured during the races and categorized according to 3 intensity zones: Z1 (below the ventilatory threshold [VT]), Z2 (between the VT and the respiratory compensation threshold [RCT]), and Z3 (above the RCT). The training impulse (TRIMP) was calculated by multiplying the sum of the time spent in each zone by 1, 2, and 3, respectively. Time spent in Z1, Z2, and daily TRIMP were significantly higher (p < 0.05) in Junior than in Youth in both single-day races (21.6 ± 1.9 min vs. 14.8 ± 1.6 min, 55.4 ± 2.3 min vs. 34.7 ± 1.9 min, and 257 ± 6 vs. 194 ± 6, respectively) and stage races (49.2 ± 3.4 min vs. 23.5 ± 4.7 min, 51.2 ± 2.6 min vs. 35.3 ± 3.7 min, and 201 ± 10 vs. 147 ± 7, respectively). In Youth and Junior, time and percentage time spent in Z3 and daily TRIMP were also significantly higher (p < 0.05) in single-day races (39.0 ± 1.9 min, 40.2 ± 1.9% and 225 ± 7) than in stage races (13.9 ± 1.8 min, 15.2 ± 1.8% and 174 ± 8). In conclusion, the present study showed that races in both Youth and Junior categories are highly demanding and that their intensity and exercise load are related to the total race duration.

The influence of breathing mechanics on the development of the slow component of O2 uptake

We examined the influence of operational lung volumes and mean inspiratory flow on the amplitude of the slow component of O₂uptake (V(O)₂(SC) ) during constant-load cycling performed below and above the respiratory compensation threshold (RCT) in young (24±1yr), healthy individuals (n=10). Subjects demonstrated a significantly greater rise in expiratory reserve volume (ERV) and mean inspiratory flow over the V(O)₂(SC) period during exercise performed above compared with below the RCT (P<0.05). Inspiratory reserve volume (IRV) was, on average, smaller for trials performed above relative to below the RCT (P<0.05). The difference in the magnitudes of change in ERV and mean inspiratory flow, but not IRV, were positively correlated with the increase in V(O)₂(SC) amplitude between work rates (R(2)=0.86, P<0.01). These findings suggest that dynamic hyperinflation and mean inspiratory flow (by increasing inspiratory resistive work) contribute to the development of the V(O)₂(SC') , particularly when exercise is performed above the RCT.

Cerebral oxygenation changes relative to the respiratory compensation threshold in untrained and trained cyclists

Cerebral oxygenation changes relative to the respiratory compensation threshold in untrained and trained cyclists

Breathing He–O2 attenuates the slow component of O2 uptake kinetics during exercise performed above the respiratory compensation threshold

The contribution of respiratory muscle O2 uptake to the development of the slow component of O2 uptake kinetics is unclear. The aim of the present study was to examine the impact of respiratory muscle unloading (via breathing, a He–O2 mixture) on the amplitude of during exercise performed below (B‐RCT) and above the respiratory compensation threshold (A‐RCT). We hypothesized that breathing He–O2 would reduce the amplitude of the by a greater amount during exercise performed A‐RCT than B‐RCT. Eight healthy male recreational cyclists performed constant‐load cycling in four sets of conditions: (1) B‐RCT breathing normal air; (2) B‐RCT breathing He–O2; (3) A‐RCT breathing normal air; and (4) A‐RCT breathing He–O2. Breathing He–O2 did not significantly attenuate the during exercise performed B‐RCT (–3 ± 14%, P &gt; 0.05). However, breathing He–O2 significantly reduced the during exercise A‐RCT (–45 ± 6%, P &lt; 0.05). The attenuated while breathing He–O2 is likely to reflect a decreased . Minute ventilation was not different between normal air and He–O2 breathing trials either B‐RCT or A‐RCT. However, operating lung volume was significantly lower when breathing He–O2 during exercise performed A‐RCT (–12 ± 3%, P &lt; 0.05). These findings suggest that comprises a greater proportion of the when exercise is performed A‐RCT compared with B‐RCT. Therefore, the impact of breathing He–O2 was more pronounced during exercise A‐RCT. Furthermore, changes in operating lung volume and the work of breathing appear to play an important role in the development of the .

Restoration of blood pH between repeated bouts of high-intensity exercise: effects of various active-recovery protocols

To determine which active-recovery protocol would reduce faster the high blood H(+) and lactate concentrations produced by repeated bouts of high-intensity exercise (HIE). On three occasions, 11 moderately trained males performed 4 bouts (1.5 min) at 163% of their respiratory compensation threshold (RCT) interspersed with active-recovery: (1) 4.5 min pedalling at 24% RCT (S(HORT)); (2) 6 min at 18% RCT (M(EDIUM)); (3) 9 min at 12% RCT (L(ONG)). The total work completed during recovery was the same in all three trials. Respiratory gases and arterialized-blood samples were obtained during exercise. At the end of exercise, L(ONG) in comparison to S(HORT) and M(EDIUM) increased plasma pH (7.32 +/- 0.02 vs. approximately 7.22 +/- 0.03; P < 0.05), while reduced lactate concentration (8.5 +/- 0.9 vs. approximately 10.9 +/- 0.8 mM; P < 0.05). Ventilatory equivalent for CO(2) was higher in L(ONG) than S(HORT) and M(EDIUM) (31.4 +/- 0.5 vs. approximately 29.6 +/- 0.5; P < 0.05). Low-intensity prolonged recovery between repeated bouts of HIE maximized H(+) and lactate removal likely by enhancing CO(2) unloading.

Illuminating the Black Box: Investigating Prefrontal Cortical Hemodynamics during Exercise with Near-Infrared Spectroscopy

Near-infrared spectroscopy (NIRS) presents an appealing option for investigating hemodynamic changes in the cerebral cortex during exercise. This review examines the physical basis of NIRS and the types of available instruments. Emphasis is placed on the physiological interpretation of NIRS signals. Theories from affective neuroscience and exercise psychobiology, including Davidson's prefrontal asymmetry hypothesis, Dietrich's transient hypofrontality hypothesis, and Ekkekakis's dual-mode model, are reviewed, highlighting the potential for designing NIRS-based tests in the context of exercise. Findings from 28 studies involving acute bouts of exercise are summarized. These studies suggest that the oxygenation of the prefrontal cortex increases during mild-to-moderate exercise and decreases during strenuous exercise, possibly proximally to the respiratory compensation threshold. Future studies designed to test hypotheses informed by psychological theories should help elucidate the significance of these changes for such important concepts as cognition, affect, exertion, and central fatigue.

Endurance Performance: Genes or Gene Combinations?

We assessed the possible association between variants of the genes encoding for the angiotensin-converting enzyme ( ACE) and alpha-actinin-3 ( ACTN3) (both individually and combined) and several endurance phenotypic traits, e.g., peak power output (PPO), ventilatory (VT) and respiratory compensation threshold (RCT), among others, in professional road cyclists and sedentary controls (n = 46 each). We applied an ANCOVA test using the aforementioned phenotype traits as dependent variables, ACE and/or ACTN3 genotype as the fixed (independent) factor and age and body mass as covariates. We only found a significant genotype effect with no concomitant covariate effect for ACTN3, with cyclists who were not alpha-actinin-3 deficient (RR + RX genotypes) having higher PPO and VT values than their XX counterparts (mean [SEM]: 7.4 (0.1) vs. 7.1 (0.1) W/kg, p = 0.035; and 4.5 (0.1) vs. 4.3 (0.1) W/kg, p = 0.029, respectively). Cyclists with an "extreme" ACTN3 and ACE genotype combination, i.e., most strength/power oriented (DD + RR/RX), had higher RCT values than those with the "intermediate" combinations (II + RX/RR, p = 0.036; and DD + XX, p = .0004) but similar to those with the most endurance oriented genotype (II + XX). No significant differences (p > 0.05) were found in controls. In summary, in world-class cyclists, we only found an association between ACTN3 genotypes and VT and PPO, and between ACTN3/ACE genotype combinations and RCT.

MONITORING EXERCISE TRAINING

Classification(s): Exercise Physiology; Exercise Training Introduction: Although there are established guidelines for exercise training, understanding the exercise training response requires an integration of the intensity and duration of training. For heart rate (HR) based methods of exercise prescription, this is particularly important since HR is not usually maintained at a constant level. Purpose: This study compared a HR based method of evaluating training based on HR zones with the session RPE method. Design: Laboratory correlated observational study. Methods: Healthy volunteers (age 18–60) (n = 27) including fitness participants and athletes performed laboratory testing to define Vo2 (55.2 + 11.0 ml/kg) and HR (173 + 12 bpm) during maximal exercise and at ventilatory threshold (VT) (36.6 + 4.3 ml/kg and 138 + 11 bpm) and respiratory compensation threshold (RCT) (46.9 + 9.0 ml/kg and 154 + 10 bpm). Training (∼30 sessions/subject; 844 total sessions) was monitored using radio telemetry and using the session RPE method to quantitate the training impulse (TRIMPS) from HR and session RPE methods. Multiple regression was used to predict the relative importance of time in each of the zones to the session RPE. Results: Training values averaged: session duration (66 + 51 min), session RPE (4.1 + 2.1), TRIMPSRPE (304 + 379) Zone1time (46 + 36 min), Zone2time (17 + 24 min), Zone3time (4 + 9 min), and TRIMPSHR (93 + 79). The regression equation for predicting TRIMPSRPE = 4.34 * Z1 + 8.78 * Z1 + 11.32 * Z3 = 94.3 (R2 = 0.80, SEE = 160). Conclusions: The results suggest HR Zone and Session RPE methods of monitoring exercise training are well related and can be used alternatively. Based on the size of the weightings, if Zone 1 = 1 point, then Zone 2 = 2.01 points, and Zone 3 = 2.61 points.

Dissociation Between Oxygen Uptake Drift During Severe Exercise And Changes In Running Mechanics

PURPOSE: The purpose of this study was to examine the relationship between changes in total mechanical energy (ME) and oxygen consumption during treadmill running in the severe intensity domain. METHODS: Seven subjects (3 males, 4 females) volunteered for this study (mean age ±SD = 25.4 ± 2.5 yrs; mass = 66.6 ±7.0 kg). After a separate familiarization session, subjects performed an incremental treadmill test to exhaustion (1% grade, speed increment = 0.5 mph per minute) from which the ventilatory threshold, respiratory compensation threshold, and peak VO2 were determined. On a subsequent day, subjects performed a constant speed treadmill run at a speed above the respiratory compensation threshold but below the speed at VO2 peak. During this run, gas exchange data was continuously recorded. In addition, 3-D kinematic data was captured over a 10 second epoch every 30 seconds using an 8-camera Motion Analysis system at 120 Hz. The total ME was calculated using the no transfer approach for a 13 segment anthropometric model. The total ME was calculated for each epoch was normalized to J/kg/m. After removing the first minute of the run data, both VO2 and ME were regressed against time within each subject. The slopes of the individual regressions were analyzed by constructing 95% confidence intervals around the mean slopes. In addition, the correlation between the VO2 and ME slopes was calculated. RESULTS: The mean ME slope was .0093 + 0.04 J/kg/m per min (95% CI = −0.26 − 0.045) and the mean VO2 slope was 74.3 + 94.8 mlO2 per min (95% CI = −13.4 - 161.9). The correlation between the ME and VO2 slopes was negative (r=−0.75, p =0.03), although was likely driven by the leverage associated with one subject with both the largest VO2 slope and the most negative ME slope. CONCLUSIONS: The results do not support the hypothesis that increases in oxygen consumption during severe intensity running at a constant speed are driven by changes in total mechanical energy.

Mobilisation of mesenchymal cells in cardiac patients: is intense exercise necessary?

Circulating mesenchymal cells (cMCs) have a potential for regenerating damaged tissue, e.g., ischaemic myocardium. In patients (age range: 53–76 years) with stable coronary artery disease cMCs were determined before and...

Workload demands in professional multi-stage cycling races of varying duration

Objetive:To analyse and compare the workload exerted by professional cyclists in 5-day, 8-day and 21-day stage races (5-SR, 8-SR, 21-SR).Methods:The study subjects were 30 professional cyclists competing in 10 5-SR,...

IMPACT OF TRAINING INTENSITY DISTRIBUTION ON PERFORMANCE IN ENDURANCE ATHLETES

The purpose of this study was to compare the effect of 2 training programs differing in the relative contribution of training volume, clearly below vs. within the lactate threshold/maximal lactate steady state region on performance in endurance runners. Twelve subelite endurance runners (who are specialists in track events, mostly the 5,000-m race usually held during spring-summer months and who also participate in cross-country races [9–12 km] during fall and winter months) were randomly assigned to a training program emphasizing low-intensity (subthreshold) (Z1) or moderately high-intensity (between thresholds) (Z2) training intensities. At the start of the study, the subjects performed a maximal exercise test to determine ventilatory (VT) and respiratory compensation thresholds (RCT), which allowed training to be controlled based on heart rate during each training session over a 5-month training period. Subjects performed a simulated 10.4-km cross-country race before and after the training period. Training was quantified based on the cumulative time spent in 3 intensity zones: zone 1 (low intensity; VT), zone 2 (moderate intensity; between VT and RCT), and zone 3 (high intensity; RCT). The contribution of total training time spent in zones 1 and 2 was controlled to have relatively more low-intensity training in Z1 (80.5 ± 1.8% and 11.8 ± 2.0%, respectively) than in Z2 (66.8 ± 1.1% and 24.7 ± 1.5%, respectively), whereas the contribution of high-intensity (zone 3) training was similar (8.3 ± 0.7% [Z1] and 8.5 ± 1.0% [Z2]). The magnitude of the improvement in running performance was significantly greater (p = 0.03) in Z1 (−157 ± 13 seconds) than in Z2 (−121.5 ± 7.1 seconds). These results provide experimental evidence supporting the value of a relatively large percentage of low-intensity training over a long period (−5 months), provided that the contribution of high-intensity training remains sufficient.

Impact of Training Intensity Distribution on Performance in Endurance Athletes

The purpose of this study was to compare the effect of 2 training programs differing in the relative contribution of training volume, clearly below vs. within the lactate threshold/maximal lactate steady state region on performance in endurance runners. Twelve subelite endurance runners (who are specialists in track events, mostly the 5,000-m race usually held during spring-summer months and who also participate in cross-country races [9-12 km] during fall and winter months) were randomly assigned to a training program emphasizing low-intensity (subthreshold) (Z1) or moderately high-intensity (between thresholds) (Z2) training intensities. At the start of the study, the subjects performed a maximal exercise test to determine ventilatory (VT) and respiratory compensation thresholds (RCT), which allowed training to be controlled based on heart rate during each training session over a 5-month training period. Subjects performed a simulated 10.4-km cross-country race before and after the training period. Training was quantified based on the cumulative time spent in 3 intensity zones: zone 1 (low intensity; <VT), zone 2 (moderate intensity; between VT and RCT), and zone 3 (high intensity; >RCT). The contribution of total training time spent in zones 1 and 2 was controlled to have relatively more low-intensity training in Z1 (80.5 +/- 1.8% and 11.8 +/- 2.0%, respectively) than in Z2 (66.8 +/- 1.1% and 24.7 +/- 1.5%, respectively), whereas the contribution of high-intensity (zone 3) training was similar (8.3 +/- 0.7% [Z1] and 8.5 +/- 1.0% [Z2]). The magnitude of the improvement in running performance was significantly greater (p = 0.03) in Z1 (-157 +/- 13 seconds) than in Z2 (-121.5 +/- 7.1 seconds). These results provide experimental evidence supporting the value of a relatively large percentage of low-intensity training over a long period ( approximately 5 months), provided that the contribution of high-intensity training remains sufficient.