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59. Effects of Caffeine on Exercise Duration, Critical Velocity, and Ratings of Perceived Exertion During Repeated-Sprint Exercise in Physically Active Men

Author

STEIN, JESSE A., GASIER, HEATH G., GOODMAN, BLAKE D., RAMIREZ, MELITZA R., DELATORRE, BLANCA P., BEATTIE, CASSANDRA M., BARSTOW, THOMAS J., and HEINRICH, KATIE M.

Subjects
Original Research
Abstract

Caffeine improves short-to-moderate distance running performance, but the effect of caffeine on repeated sprints are equivocal. This research determined if caffeine improved exercise tolerance during repeated-sprint exercise. iCV is a running velocity that distinguishes intermittent running velocities (velocities ≤ iCV) that are sustainable from those resulting in a predictable time to exhaustion (velocities > iCV). Seven physically active men (age = 21.6 ± 1.5 years, body mass = 72.8 ± 5.1 kg, VO(2max) = 56.9 ± 9.8 mL/kg/min) ingested caffeine (5 mg/kg) or placebo (crossover design) 60 min prior to an intermittent critical velocity (iCV) test. The treadmill grade and velocity at VO(2max) (vVO(2max)) were used for iCV testing, and consisted of 3 bouts (10 sec running and 10 sec passive rest) at 130, 110 and 120% vVO(2max). Each bout continued until volitional exhaustion and was separated by 20 min of passive rest. Total distance and duration were recorded to determine exercise tolerance using the iCV model. Caffeine ingestion increased running duration at 110% vVO(2max) (p = 0.02), but not at 120 (p = 0.93) and 130% vVO(2max) (p = 0.14). Caffeine did not improve iCV model parameters. A single dose of caffeine consumed 60 min before repeated-sprints can improve performance at 110% vVO(2max), but not at higher velocities.

Published
2021

60. Dissociation between exercise intensity thresholds: Mechanistic insights from supine exercise

Author

Goulding, Richie P., Marwood, Simon, Lei, Tze Huan, Okushima, Dai, Poole, David C., Barstow, Thomas J., Kondo, Narihiko, Koga, Shunsaku, Goulding, Richie P., Marwood, Simon, Lei, Tze Huan, Okushima, Dai, Poole, David C., Barstow, Thomas J., Kondo, Narihiko, and Koga, Shunsaku

Abstract

This study tested the hypothesis that the respiratory compensation point (RCP) and breakpoint in deoxygenated [heme] [deoxy [heme]BP, assessed via near-infrared spectroscopy (NIRS)] during ramp incremental exercise would occur at the same metabolic rate in the upright (U) and supine (S) body positions. Eleven healthy men completed ramp incremental exercise tests in U and S. Gas exchange was measured breath-by-breath and time-resolved-NIRS was used to measure deoxy[heme] in the vastus lateralis (VL) and rectus femoris (RF). RCP (S: 2.56 ± 0.39, U: 2.86 ± 0.40 Lmin_1, P = 0.02) differed from deoxy[heme]BP in the VL in U (3.10 ± 0.44 Lmin_1, P = 0.002), but was not different in S in the VL (2.70 ± 0.50 Lmin_1, P = 0.15). RCP was not different from the deoxy[heme]BP in the RF for either position (S: 2.34 ± 0.48 Lmin_1, U: 2.76 ± 0.53 Lmin_1, P > 0.05). However, the deoxy[heme]BP differed between muscles in both positions (P < 0.05), and changes in deoxy[heme]BP did not relate to DRCP between positions (VL: R = 0.55, P = 0.080, RF: R = 0.26, P = 0.44). The deoxy[heme]BP was consistently preceded by a breakpoint in total[heme], and was, in turn, itself preceded by a breakpoint in muscle surface electromyography (EMG). RCP and the deoxy[heme]BP can be dissociated across muscles and different body positions and, therefore, do not represent the same underlying physiological phenomenon. The deoxy[heme]BP may, however, be mechanistically related to breakpoints in total[heme] and muscle activity.

Published
2021
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65. Effects of prior heavy exercise on heterogeneity of muscle deoxygenation kinetics during subsequent heavy exercise

Author

Saitoh, Tadashi, Ferreira, Leonardo F., Barstow, Thomas J., Poole, David C., Ooue, Anna, Kondo, Narihiko, and Kogas, Shunsaku

Subjects
Exercise -- Physiological aspects, Exercise -- Health aspects, Exercise -- Research, Biological sciences
Abstract

We investigated the effects of prior heavy exercise on the spatial heterogeneity of muscle deoxygenation kinetics and the relationship to the pulmonary 02 uptake (pV[o.sub.2]) kinetics during subsequent heavy exercise. Seven healthy men completed two 6-min bouts of heavy work rate cycling exercise, separated by 6 min of unloaded exercise. The changes in the concentration of deoxyhemoglobin/myoglobin ([DELTA]deoxy-[Hb+Mb]) were assessed simultaneously at 10 different sites on the rectus femoris muscle using multichannel near-infrared spectroscopy. Prior exercise had no effect on either the time constant or the amplitude of the primary component pV[o.sub.2], whereas it reduced the amplitude of the slow component (SC). [DELTA]Deoxy-[Hb+Mb] across all 10 sites for bout 2 displayed a shorter time delay (mean and SD for subjects: 13.5 [+ or -] 1.3 vs. 9.3 [+ or -] 1.4 s; P < 0.01) and slower primary component time constant ([tau]: 9.3 [+ or -] 1.3 vs. 17.8 [+ or -] 1.0 s; P < 0.01) compared with bout 1. Prior exercise significantly reduced both the intersite coefficient of variation (CV) of the [tau] of [DELTA]deoxy-[Hb+Mb] (26.6 [+ or -] 11.8 vs. 13.7 [+ or -] 5.6%; P < 0.01) and the point-by-point heterogeneity [root mean square error (RMSE)] during the primary component in the second bout. However, neither the change in the CV for [tau] nor RMSE of [DELTA]deoxy-[Hb+Mb] correlated with the reduction in the SC in pV[o.sub.2] kinetics during subsequent heavy exercise. In conclusion, prior exercise reduced the spatial heterogeneity of the primary component of muscle deoxygenation kinetics. This effect was not correlated with alterations in the pV[o.sub.2] response during subsequent heavy exercise. near-infrared spectroscopy; spatial heterogeneity; oxygen uptake kinetics; muscle oxygen delivery

Published
2009

68. Comparison of oxygen uptake kinetics during knee extension and cycle exercise

Author

Koga, Shunsaku, Poole, David C., Shiojiri, Tomoyuki, Kondo, Narihiko, Fukuba, Yoshiyuki, Miura, Akira, and Barstow, Thomas J.

Subjects
Oxygen consumption, Muscles, Blood flow, Biological sciences
Abstract

The knee extension exercise (KE) model engenders different muscle and fiber recruitment patterns, blood flow, and energetic responses compared with conventional cycle ergometry (CE). This investigation had two aims: 1) to test the hypothesis that upright two-leg KE and CE in the same subjects would yield fundamentally different pulmonary [O.sub.2] uptake (p[Vo.sub.2],) kinetics and 2) to characterize the muscle blood flow, muscle [Vo.sub.2] (m[Vo.sub.2]), and p[Vo.sub.2] kinetics during KE to investigate the rate-limiting factor(s) of p[Vo.sub.2] on kinetics and muscle energetics and theft mechanistic bases after the onset of heavy exercise. Six subjects performed KE and CE transitions from unloaded to moderate [< ventilatory threshold (VT)I and heavy (>VT) exercise. In addition to p[Vo.sub.2] during CE and KE, simultaneous pulsed and echo Doppler methods, combined with blood sampling from the femoral vein, were used to quantify the precise temporal profiles of femoral artery blood flow (LBF) and m[Vo.sub.2] at the onset of KE. First, the gain (amplitude/work rate) of the primary component of p[Vo.sub.2] for both moderate and heavy exercise was higher during KE (~12 ml x [W.sup.-1] x [min.sup.-1]) compared with CE (~10), but the time constants for the primary component did not differ. Furthermore, the mean response time (MRT) and the contribution of the slow component to the overall response for heavy KE were significantly greater than for CE. Second, the time constant for the primary component of m[Vo.sub.2] during heavy KE [25.8 [+ or -] 9.0 s (SD)I was not significantly different from that of the phase 11 p[Vo.sub.2]. Moreover, the slow component of p[Vo.sub.2] evident for the heavy KE reflected the gradual increase in m[Vo.sub.2]. The initial LBF kinetics after onset of KE were significantly faster than the phase II p[Vo.sub.2] kinetics (moderate: time constant LBF - 8.0 [+ or -] 3.5 s, p[Vo.sub.2] = 32.7 [+ or -] 5.6 s. P < 0.05: heavy: LBF = 9.7 = 2.0 s, p[Vo.sub.2] = 29.9 + 7.9 s, P < 0.05). The MRT of LBF was also significantly faster than that of p[Vo.sub.2]. These data demonstrate that the energetics (as gain) tot KE are greater than for CE, but the kinetics of adjustment (as time constant for the primary component) are similar. Furthermore, the kinetics of muscle blood flow during KE are faster than those of pVo2, consistent with an intramuscular limitation to [Vo.sub.2] kinetics, i.e., a microvascular [O.sub.2] delivery-lo-[O.sub.2], requirement mismatch or oxidative enzyme inertia. pulmonary oxygen uptake kinetics: muscle oxygen consumption: muscle blood flow

Published
2005

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