Long-Term Alterations in Pulmonary V˙O2 and Muscle Deoxygenation On-Kinetics During Heavy-Intensity Exercise in Competitive Youth Cyclists: A Cohort Study.

PURPOSE: The aim of this investigation was to assess alterations of pulmonary oxygen uptake (V˙O2) and muscle deoxygenation on-kinetics during heavy-intensity cycling in youth cyclists over a period of 15 months. METHODS: Eleven cyclists (initial age, 14.3 [1.6] y; peak V˙O2, 62.2 [4.5] mL·min-1·kg-1) visited the laboratory twice on 3 occasions within 15 months. Participants performed an incremental ramp exercise test and a constant workrate test within the heavy-intensity domain during the first visit and second visit, respectively. Subsequently, parameter estimates of the V˙O2 and muscle deoxygenation on-kinetics were determined with mono-exponential models. RESULTS: The V˙O2 phase II time constant decreased from occasion 1 (34 [4] s) to occasion 2 (30 [4] s, P = .005) and 3 (28 [4] s, P = .010). However, no significant alteration was observed between occasions 2 and 3 (P = .565). The V˙O2 slow component amplitude either expressed in absolute values (ie, L·min-1) or relative to end exercise V˙O2 (ie, %) showed no significant changes throughout the study (P = .972 and .996). Furthermore, the muscle deoxygenation on-kinetic mean response time showed no significant changes throughout the study (18 [8], 18 [3], and 16 [5] s for occasions 1, 2, and 3, respectively; P = .279). CONCLUSION: These results indicate proportional enhancements of local muscle oxygen distribution and utilization, which both contributed to the speeding of the V˙O2 on-kinetics herein.

Physiological Characteristics of Competitive Male Junior Cyclists Transitioning to the Under-23 Level: A Retrospective Comparative Study.

PURPOSE: The purpose of the current investigation was to retrospectively assess possible differences in physiological performance characteristics between junior cyclists signing a contract with an under-23 (U23) development team versus those failing to sign such a contract. METHODS: Twenty-five male junior cyclists (age: 18.1 [0.7] y, stature: 181.9 [6.0] cm, body mass: 69.1 [7.9] kg, peak oxygen uptake: 71.3 [6.2] mL·min-1·kg-1) were assigned to this investigation. Between September and October of the last year in the junior category, each cyclist performed a ramp incremental exercise test to determine certain physiological performance characteristics. Subsequently, participants were divided in 2 groups: (1) those signing a contract with a U23 development team (JUNIORU23) and (2) those failing to sign such a contract (JUNIORNON-U23). Unpaired t tests were used to assess possible between-groups differences in physiological performance characteristics. The level of statistical significance was set at P < .05 two tailed. RESULTS: No significant between-groups differences in submaximal (ie, gas exchange threshold, respiratory compensation point) and maximal physiological performance characteristics (ie, peak work rate, peak oxygen uptake) expressed in absolute values (ie, L·min-1, W) were observed (P > .05). However, significant between-groups differences were observed when physiological performance characteristics were expressed relative to the cyclists' body weights (P < .05). CONCLUSIONS: The current investigation showed that junior cyclists stepping up to a U23 development team might be retrospectively differentiated from junior cyclists not stepping up based on certain physiological performance characteristics, which might inform practitioners and/or federations working with young cyclists during the long-term athletic development process.

Alterations in aerobic fitness and muscle deoxygenation during ramp incremental exercise in trained youth cyclists: a ~3-year longitudinal study.

Alterations of aerobic fitness and muscle deoxygenation during a ramp incremental exercise test (GXT) were assessed on two occasions within a time-frame of 2.9 ± 0.1y in competitive youth cyclists. Nine cyclists (age, 14.5 ± 1.1y; peak oxygen uptake (V˙O2peak), 62.6 ± 4.2 mL.min-1.kg-1) participated in this investigation. V˙O2peak, the gas exchange threshold (GET) and the respiratory compensation point (RCP), as well as the muscle deoxygenation response pattern were determined during a GXT using open circuit spirometry and near-infrared spectroscopy, respectively. T-tests and Pearson's correlations were used to assess effects of time on the dependent variables and relationships between changes of parameter estimates of aerobic fitness and the muscle deoxygenation response, respectively. Workrate and metabolic rate at GET (33 ± 20 and 42 ± 23%) and RCP (36 ± 20 and 40 ± 22%), and V˙O2peak (30 ± 18%) significantly increased throughout the study (P < 0.05). The muscle deoxygenation response showed a significant rightward shift from occasion one to two (P < 0.05). Alterations in the workrate/metabolic rate at RCP, and V˙O2peak, were correlated with alterations of the muscle deoxygenation response (R = 0.71-0.89, P < 0.05). Together, this is thought to indicate a superior muscle perfusion within the tissue of interrogation at the same metabolic rate on occasion two vs. one, which partially contributed to the improved aerobic fitness in the cyclists herein.

Longitudinal alterations of pulmonary V . O2 on-kinetics during moderate-intensity exercise in competitive youth cyclists are related to alterations in the balance between microvascular O2 distribution and muscular O2 utilization.

Purpose: The main purpose of the current study was to investigate the dynamic adjustment of pulmonary oxygen uptake ( V . O2) in response to moderate-intensity cycling on three occasions within 15 months in competitive youth cyclists. Furthermore, the muscle Δdeoxy[heme] on-kinetics and the Δdeoxy[heme]-to- V . O2 ratio were modeled to examine possible mechanistic basis regulating pulmonary V . O2 on-kinetics. Methods: Eleven cyclists (initial age, 14.3 ± 1.6 y; peak V . O2, 62.2 ± 4.5 mL.min-1.kg-1) with a training history of 2-5 years and a training volume of ~10 h per week participated in this investigation. V . O2 and Δdeoxy[heme] responses during workrate-transitions to moderate-intensity cycling were measured with breath-by-breath spirometry and near-infrared spectroscopy, respectively, and subsequently modeled with mono-exponential models to derive parameter estimates. Additionally, a normalized Δdeoxy[heme]-to- V . O2 ratio was calculated for each participant. One-way repeated-measures ANOVA was used to assess effects of time on the dependent variables of the responses. Results: The V . O2 time constant remained unchanged between the first (~24 s) and second visit (~22 s, P > 0.05), whereas it was significantly improved through the third visit (~13 s, P = 0.006-0.013). No significant effects of time were revealed for the parameter estimates of the Δdeoxy[heme] response (P > 0.05). A significant Δdeoxy[heme]-to- V . O2 ratio "overshoot" was evident on the first (1.09 ± 0.10, P = 0.006) and second (1.05 ± 0.09, P = 0.047), though not the third (0.97 ± 0.10, P > 0.05), occasion. These "overshoots" showed strong positive relationships with the V . O2 time constant during the first (r = 0.66, P = 0.028) and second visit (r = 0.76, P = 0.007). Further, strong positive relationships have been observed between the individual changes of the fundamental phase τp and the Δdeoxy[heme]-to- V . O2 ratio "overshoot" from occasion one to two (r = 0.70, P = 0.017), and two to three (r = 0.74, P = 0.009). Conclusion: This suggests that improvements in muscle oxygen provision and utilization capacity both occurred, and each may have contributed to enhancing the dynamic adjustment of the oxidative "machinery" in competitive youth cyclists. Furthermore, it indicates a strong link between an oxygen maldistribution within the tissue of interrogation and the V . O2 time constant.

Elite versus non-elite cyclist - Stepping up to the international/elite ranks from U23 cycling.

This study investigated the physiological, performance and training characteristics of U23 cyclists and assessed the requirements of stepping up to the elite/international ranks. Twenty highly trained U23 cyclists (age, 22.1 ± 0.8 years; body mass, 69.1 ± 6.8 kg; VO2max, 76.1 ± 3.9 ml·kg-1·min-1) participated in this study. The cyclists were a posteriori divided into two groups based on whether or not they stepped up to elite/international level cycling (U23ELITE vs. U23NON-ELITE). Physiological, performance and training and racing characteristics were determined and compared between groups. U23ELITE demonstrated higher absolute peak power output (p = .016), 2 min (p = .026) 5 min (p = .042) and 12 min (p ≤ .001) power output as well as higher absolute critical power (p = .002). Further, U23ELITE recorded more accumulated hours (p ≤ .001), covered distance (p ≤ .001), climbing metres (p ≤ .001), total sessions (p ≤ .001), total work (p ≤ .001) and scored more UCI points (p ≤ .001). These findings indicate that U23ELITE substantially differed from U23NON-ELITE regarding physiological, performance and training and racing characteristics derived from laboratory and field. These variables should be considered by practitioners supporting young cyclists throughout their development towards the elite/international ranks.

Effects of Flat and Uphill Cycling on the Power-duration Relationship.

The purpose of this study was to investigate the effects of flat and uphill cycling on critical power and the work available above critical power. Thirteen well-trained endurance athletes performed three prediction trials of 10-, 4- and 1-min in both flat (0.6%) and uphill (9.8%) cycling conditions on two separate days. Critical power and the work available above critical power were estimated using various mathematical models. The best individual fit was used for further statistical analyses. Paired t-tests and Bland-Altman plots with 95% limits of agreement were applied to compare power output and parameter estimates between cycling conditions. Power output during the 10- and 4-min prediction trial and power output at critical power were not significantly affected by test conditions (all at p>0.05), but the limits of agreement between flat and uphill cycling power output and critical power estimates are too large to consider both conditions as equivalent. However, power output during the 1-min prediction trial and the work available above critical power were significantly higher during uphill compared to flat cycling (p<0.05). The results of this investigation indicate that gradient affects cycling time-trial performance, power output at critical power, and the amount of work available above critical power.