Roger C. Harris

The time course of phosphorylcreatine resynthesis during recovery of the quadriceps muscle in man.

SummaryThe time course of phosphorylcreatine (PC) resynthesis in the human m. quadriceps femoris was studied during recovery from exhaustive dynamic exercise and from isometric contraction sustained to fatigue. The immediate postexercise muscle PC content after either form of exercise was 15–16% of the resting muscle content. The time course of PC resynthesis during recovery was biphasic exhibiting a fast and a slow recovery component. The half-time for the fast component was 21–22 s but this accounted for a smaller fraction of the total PC restored during recovery from the isometric contraction than after the dynamic exercise. The half-time for the slow component was in each case more than 170 s. After 2 and 4 min recovery the total amounts of PC resynthesized after the isometric exercise were significantly lower than from the dynamic exercise.Occlusion of the circulation to the quadriceps completely abolished the resynthesis of PC. Restoration of resynthesis occurred only after release of occlusion.

Lactate content and pH in muscle samples obtained after dynamic exercise

SummaryAnalyzes were made on muscle samples taken from the lateral part of the m. quadriceps femoris of man (lactate, pyruvate, and pH) on venous blood (lactate, pyruvate) and on capillary blood (pH). Samples were taken at rest, immediately after termination of dynamic exercise and during 20 min recovery from exhaustive dynamic exercise.Muscle pH decreased from 7.08 at rest to 6.60 at exhaustion. Decrease in muscle pH was linearly related to muscle content of lactate + pyruvate. The relationship was slightly different from what has been obtained after isometric exercise and this difference was ascribed to acid-base exchange with the blood during dynamic exercise.Lactate content was highly elevated in muscle after exercise and the concentration was 2–3 times higher than in blood. Pyruvate content was, however, only slightly higher than that at rest. During recovery lactate content of muscle decreased exponentially with respect to time, whereas pyruvate content increased. The half-time of lactate decrease was 9.5 min. From the lactate dehydrogenase equilibrium relative values on NADH/NAD ratio could be calculated. It was found that NADH/NAD was highly increased after exercise and that it had not returned to the basal value after 20 min recovery.

The absorption of orally supplied β-alanine and its effect on muscle carnosine synthesis in human vastus lateralis

Summary.β-Alanine in blood-plasma when administered as A) histidine dipeptides (equivalent to 40 mg · kg−1 bwt of β-alanine) in chicken broth, or B) 10, C) 20 and D) 40 mg · kg−1 bwt β-alanine (CarnoSyn™, NAI, USA), peaked at 428 ± SE 66, 47 ± 13, 374 ± 68 and 833 ± 43 µM. Concentrations regained baseline at 2 h. Carnosine was not detected in plasma with A) although traces of this and anserine were found in urine. Loss of β-alanine in urine with B) to D) was <5%. Plasma taurine was increased by β-alanine ingestion but this did not result in any increased loss via urine. Pharmacodynamics were further investigated with 3 × B) per day given for 15 d. Dietary supplementation with I) 3.2 and II) 6.4 g · d−1 β-alanine (as multiple doses of 400 or 800 mg) or III) L-carnosine (isomolar to II) for 4 w resulted in significant increases in muscle carnosine estimated at 42.1, 64.2 and 65.8%.

Influence of β-alanine supplementation on skeletal muscle carnosine concentrations and high intensity cycling capacity

Summary.Muscle carnosine synthesis is limited by the availability of β-alanine. Thirteen male subjects were supplemented with β-alanine (CarnoSyn™) for 4 wks, 8 of these for 10 wks. A biopsy of the vastus lateralis was obtained from 6 of the 8 at 0, 4 and 10 wks. Subjects undertook a cycle capacity test to determine total work done (TWD) at 110% (CCT110%) of their maximum power (Wmax). Twelve matched subjects received a placebo. Eleven of these completed the CCT110% at 0 and 4 wks, and 8, 10 wks. Muscle biopsies were obtained from 5 of the 8 and one additional subject. Muscle carnosine was significantly increased by +58.8% and +80.1% after 4 and 10 wks β-alanine supplementation. Carnosine, initially 1.71 times higher in type IIa fibres, increased equally in both type I and IIa fibres. No increase was seen in control subjects. Taurine was unchanged by 10 wks of supplementation. 4 wks β-alanine supplementation resulted in a significant increase in TWD (+13.0%); with a further +3.2% increase at 10 wks. TWD was unchanged at 4 and 10 wks in the control subjects. The increase in TWD with supplementation followed the increase in muscle carnosine.

Effects of β-alanine supplementation on the onset of neuromuscular fatigue and ventilatory threshold in women

Summary.This study examined the effects of 28 days of β-alanine supplementation on the physical working capacity at fatigue threshold (PWCFT), ventilatory threshold (VT), maximal oxygen consumption (

Effect of beta-alanine supplementation on muscle carnosine concentrations and exercise performance

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Resynthesis of creatine phosphate in human muscle after exercise in relation to intramuscular pH and availability of oxygen

O2-MAX), and time-to-exhaustion (TTE) in women. Twenty-two women (age ± SD 27.4 ± 6.1 yrs) participated and were randomly assigned to either the β-alanine (CarnoSyn™) or Placebo (PL) group. Before (pre) and after (post) the supplementation period, participants performed a continuous, incremental cycle ergometry test to exhaustion to determine the PWCFT, VT,

Muscle buffering capacity and dipeptide content in the Thoroughbred horse, Greyhound dog and man

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Effects of exercise intensity and environmental stress on indices of oxidative stress and iron homeostasis during exercise in the horse.

O2-MAX, and TTE. There was a 13.9, 12.6 and 2.5% increase (p < 0.05) in VT, PWCFT, and TTE, respectively, for the β-alanine group, with no changes in the PL (p > 0.05). There were no changes for

Carnosine and anserine concentrations in the quadriceps femoris muscle of healthy humans

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