28 research outputs found
Relationship between (non)linear phase II pulmonary oxygen uptake kinetics with skeletal muscle oxygenation and age in 11 to 15 y olds
This is the author accepted manuscript. the final version is available from Wiley via the DOI in this recordThis study investigated in nineteen male youth (mean age: 13.6 ± 1.1 y, range: 11.7 â
15.7 y) the relationship between pulmonary oxygen uptake ( o2) and muscle
deoxygenation kinetics during moderateâ and very heavyâintensity âstepâ cycling
initiated from unloaded pedaling (i.e. UâM and UâVH) and moderateâtoâvery heavyâ
intensity step cycling (i.e. MâVH). Pulmonary o2 was measured breathâbyâbreath and
tissue oxygenation index (TOI) of the vastus lateralis using nearâinfrared spectroscopy.
There were no significant differences in the phase II time constant (Ï o2p) between
UâM and UâVH (23 ± 6 s vs. 25 ± 7 s; P = 0.36); however, the Ï o2p was slower during
MâVH (42 ± 16 s) compared to other conditions (P < 0.001). Quadriceps TOI decreased
with a faster (P < 0.01) mean response time (MRT; i.e. time delay + Ï) during UâVH (14
± 2 s) compared to UâM (22 ± 4 s) and MâVH (20 ± 6 s). The difference (Î) between
the Ï o2p and MRTâTOI was greater during UâVH compared to UâM (12 ± 7 vs. 2 ± 7 s,
P < 0.001) and during MâVH (23 ± 15 s) compared to other conditions (P < 0.02),
suggesting an increased proportional speeding of fractional O2 extraction. The slowing
of the Ï o2p during MâVH relative to UâM and UâVH correlated positively with
chronological age (r = 0.68 and 0.57, respectively, P < 0.01). In youth, âworkâtoâworkâ
transitions slowed microvascular O2 deliveryâtoâO2 utilization with alterations in phase
II o2 dynamics accentuated between the ages of 11 to 15 y
Testâretest reliability of pulmonary oxygen uptake and muscle deoxygenation during moderate- and heavy-intensity cycling in youth elite-cyclists
This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this recordTo establish the test-retest reliability of pulmonary oxygen uptake ( O2), muscle
deoxygenation (deoxy[heme]) and tissue oxygen saturation (StO2) kinetics in youth elitecyclists.
From baseline pedaling, 15 youth cyclists completed 6-min step transitions to a
moderate- and heavy-intensity work rate separated by 8 min of baseline cycling. The protocol
was repeated after 1 h of passive rest. O2 was measured breath-by-breath alongside
deoxy[heme] and StO2 of the vastus lateralis by near-infrared spectroscopy. Reliability was
assessed using 95% limits of agreement (LoA), the typical error (TE) and the intraclass
correlation coefficient (ICC). During moderate- and heavy-intensity step cycling, TEs for the
amplitude, time delay and time constant ranged between 3.5-21.9% and 3.9-12.1% for O2 and
between 6.6-13.7% and 3.5-10.4% for deoxy[heme], respectively. The 95% confidence interval
for estimating the kinetic parameters significantly improved for ensemble-averaged transitions
of O2 (p<0.01) but not for deoxy[heme]. For StO2, the TEs for the baseline, end-exercise and
the rate of deoxygenation were 1.0-42.5% and 1.1-5.5% during moderate- and heavy-intensity
exercise, respectively. The ICC ranged from 0.81-0.99 for all measures. Test-retest reliability
data provides limits within which changes in O2, deoxy[heme] and StO2 kinetics may be
interpreted with confidence in youth athletes
Pulmonary oxygen uptake and muscle deoxygenation kinetics during recovery in trained and untrained male adolescents
Previous studies have demonstrated faster pulmonary oxygen uptake ( V Ë O 2 ) kinetics in the trained state during the transition to and from moderate-intensity exercise in adults. Whilst a similar effect of training status has previously been observed during the on-transition in adolescents, whether this is also observed during recovery from exercise is presently unknown. The aim of the present study was therefore to examine V Ë O 2 kinetics in trained and untrained male adolescents during recovery from moderate-intensity exercise. 15 trained (15 ± 0.8 years, V Ë O 2max 54.9 ± 6.4 mL kgâ1 minâ1) and 8 untrained (15 ± 0.5 years, V Ë O 2max 44.0 ± 4.6 mL kgâ1 minâ1) male adolescents performed two 6-min exercise off-transitions to 10 W from a preceding âbaselineâ of exercise at a workload equivalent to 80% lactate threshold; V Ë O 2 (breath-by-breath) and muscle deoxyhaemoglobin (near-infrared spectroscopy) were measured continuously. The time constant of the fundamental phase of V Ë O 2 off-kinetics was not different between trained and untrained (trained 27.8 ± 5.9 s vs. untrained 28.9 ± 7.6 s, P = 0.71). However, the time constant (trained 17.0 ± 7.5 s vs. untrained 32 ± 11 s, P < 0.01) and mean response time (trained 24.2 ± 9.2 s vs. untrained 34 ± 13 s, P = 0.05) of muscle deoxyhaemoglobin off-kinetics was faster in the trained subjects compared to the untrained subjects. V Ë O 2 kinetics was unaffected by training status; the faster muscle deoxyhaemoglobin kinetics in the trained subjects thus indicates slower blood flow kinetics during recovery from exercise compared to the untrained subjects
Beetroot supplementation improves the physiological responses to incline walking
The final publication is available at Springer via http://dx.doi.org/10.1007/s00421-018-3843-xPurpose: We investigated the effects of an acute 24-h nitrate-rich beetroot juice supplement (BR) on the energy cost, exercise efficiency and blood pressure responses to intermittent walking at different gradients. Methods: In a double-blind, cross-over design, eight participants were provided with a total of 350 ml of nitrate-rich (~20.5 mmol nitrate) BR or placebo (PLA) across 24-h before completing intermittent walking at 3 km/h on treadmill at gradients of 1%, 5%, 10%, 15% and 20%. Results: Resting mean arterial pressure (MAP) was ~4.1% lower after BR (93 vs. 89 mmHg; P = 0.001), as well as during exercise (102 vs. 99 mmHg; P = 0.011) and recovery (97 vs. 94 mmHg; P = 0.001). Exercising (1227 vs. 1129 ml/min P < 0.001) and end-stage (1404 vs. 1249 ml/min; P = 0.002) oxygen uptake (O2) was lower in BR compared to PLA, which was accompanied by an average reduction in phase II ÌO2 amplitude (1067 vs. 940 ml/min; P = 0.025). Similarly, recovery O2 (509 vs. 458 ml/min; P = 0.001) was lower in BR. Whole-blood potassium concentration increased from pre-post exercise in PLA (4.1 ± 0.3 vs. 4.5 ± 0.3 mmol/L; P = 0.013) but not BR (4.1 ± 0.31 vs. 4.3 ± 0.2 mmol/L; P = 0.188). Conclusions: Energy cost of exercise, recovery of O2, MAP and blood markers were ameliorated after BR. Previously reported mechanisms explain these findings, which are more noticeable during less efficient walking at steep gradients (15-20%). These findings have practical implications for hill-walkers
Influence of dietary nitrate supplementation on local sweating and cutaneous vascular responses during exercise in a hot environment.
Purpose We investigated the influence of inorganic nitrate (NOâ3) supplementation on local sweating and cutaneous vascular
responses during exercise in hot conditions.
Method Eight healthy, young subjects were assigned in a randomized, double-blind, crossover design to receive NOâ3 -rich
beetroot (BR) juice (140 mL/day, containing ~8 mmol of NOâ3) and NOâ3-depleted placebo (PL) juice (140 mL/day, containing ~0.003 mmol of NOâ3) for 3 days. On day 3 of supplementation, subjects cycled at an intensity corresponding to 55% of VÌ O2max for 30 min in hot conditions (30 °C, 50% relative humidity). Chest and forearm sweat rate (SR) and skin blood flow (SkBF), were measured continuously. Cutaneous vascular conductance (CVC) was calculated by SkBF/mean arterial pressure (MAP).
Results Prior to exercise, plasma NOâ
3 (21±6 and 581±161 ”M) and nitrite (NOâ
2 , 87±28 and 336±156 nM) concentrations
were higher after BR compared to PL supplementation (Pâ€0.011, n=6). Oesophageal, mean skin, and mean body temperatures during exercise were not different between conditions. In addition, BR supplementation did not affect SR, SkBF, and CVC during exercise. A lower MAP was found after 30 min of exercise following BR supplementation (112±6 and 103±6 mmHg for PL and BR, respectively, P=0.021). Conclusion These results suggest that inorganic NOâ
3 supplementation, which increases the potential for O2-independent NO
production, does not affect local sweating and cutaneous vascular responses, but attenuates blood pressure in young healthy
subjects exercising in a hot environment
ââBeet-ingââ the Mountain: A Review of the Physiological and Performance Effects of Dietary Nitrate Supplementation at Simulated and Terrestrial Altitude
Exposure to altitude results in multiple physiological consequences. These include, but are not limited to, a reduced maximal oxygen consumption, drop in arterial oxygen saturation, and increase in muscle metabolic perturbations at a fixed sub-maximal work rate. Exercise capacity during fixed work rate or incremental exercise and time-trial performance are also impaired at altitude relative to sea-level. Recently, dietary nitrate (NO3-) supplementation has attracted considerable interest as a nutritional aid during altitude exposure. In this review, we summarise and critically evaluate the physiological and performance effects of dietary NO3- supplementation during exposure to simulated and terrestrial altitude. Previous investigations at simulated altitude indicate that NO3- supplementation may reduce the oxygen cost of exercise, elevate arterial and tissue oxygen saturation, improve muscle metabolic function, and enhance exercise capacity/ performance. Conversely, current evidence suggests that NO3- supplementation does not augment the training response at simulated altitude. Few studies have evaluated the effects of NO3- at terrestrial altitude. Current evidence indicates potential improvements in endothelial function at terrestrial altitude following NO3- supplementation. No effects of NO3- supplementation have been observed on oxygen consumption or arterial oxygen saturation at terrestrial altitude, although further research is warranted. Limitations of the present body of literature are discussed, and directions for future research are provided
Validity of Treadmill-Derived Critical Speed on Predicting 5000-Meter Track-Running Performance.
Nimmerichter, A, Novak, N, Triska, C, Prinz, B, and Breese, BC. Validity of treadmill-derived critical speed on predicting 5,000-meter track-running performance. J Strength Cond Res 31(3): 706-714, 2017-To evaluate 3 models of critical speed (CS) for the prediction of 5,000-m running performance, 16 trained athletes completed an incremental test on a treadmill to determine maximal aerobic speed (MAS) and 3 randomly ordered runs to exhaustion at the [INCREMENT]70% intensity, at 110% and 98% of MAS. Critical speed and the distance covered above CS (D') were calculated using the hyperbolic speed-time (HYP), the linear distance-time (LIN), and the linear speed inverse-time model (INV). Five thousand meter performance was determined on a 400-m running track. Individual predictions of 5,000-m running time (t = [5,000-D']/CS) and speed (s = D'/t + CS) were calculated across the 3 models in addition to multiple regression analyses. Prediction accuracy was assessed with the standard error of estimate (SEE) from linear regression analysis and the mean difference expressed in units of measurement and coefficient of variation (%). Five thousand meter running performance (speed: 4.29 ± 0.39 m·s; time: 1,176 ± 117 seconds) was significantly better than the predictions from all 3 models (p < 0.0001). The mean difference was 65-105 seconds (5.7-9.4%) for time and -0.22 to -0.34 m·s (-5.0 to -7.5%) for speed. Predictions from multiple regression analyses with CS and D' as predictor variables were not significantly different from actual running performance (-1.0 to 1.1%). The SEE across all models and predictions was approximately 65 seconds or 0.20 m·s and is therefore considered as moderate. The results of this study have shown the importance of aerobic and anaerobic energy system contribution to predict 5,000-m running performance. Using estimates of CS and D' is valuable for predicting performance over race distances of 5,000 m