Biomedical subjects

R L Sharp

Publications and source records attributed to R L Sharp.

25 records · Page 2Linked to original sources

PubMed1986

Effects of eight weeks of bicycle ergometer sprint training on human muscle buffer capacity.

This investigation was undertaken to determine whether human skeletal muscle buffer capacity (BCm) is affected by training. Eight untrained males participated in 8 weeks of sprint training on bicycle ergometers. Muscle biopsy samples were taken from the vastus lateralis before and at several times following an incremental bicycle ergometer test (0 min, 5 min, 15 min). These subjects were tested before (PRE) and following (POST) the training period. Seven endurance-trained cyclists (ET) were also tested for the purpose of comparing the BCm of ET to that of PRE and POST. Biopsy samples were quick-frozen in liquid nitrogen and later analyzed for lactate concentration (HLam), homogenate pH (pHm), and creatine phosphate concentration. BCm was calculated from the change in HLam and pHm observed from rest to exhaustion and was expressed as mmol X kg-1 X pH-1 (Slykes). There was no significant difference in resting HLam or resting pHm among the groups. There was a significant difference in HLam at exhaustion between PRE (21.41 +/- 1.65 mmol X kg-1), POST (25.61 +/- 2.38 mmol X kg-1), and ET (11.16 +/- 0.31 mmol X kg-1) but no significant difference in pHm at exhaustion between PRE (6.65 +/- 0.03 pH units) and POST (6.69 +/- 0.06 pH units). pHm at exhaustion for the ET group was significantly higher than the others at 6.91 +/- 0.02 pH units. A significant difference between PRE and POST BCm was found (PRE: 44.68 +/- 3.03 S1; POST: 61.04 +/- 4.11 S1) while ET BCm (47.21 +/- 7.26 S1) was not significantly different from PRE. These data indicate that muscle buffer capacity is increased with highly intense sprint training but provide no evidence to suggest that muscle buffer capacity is affected by endurance training.

Adult↗

PubMed1984

Skeletal muscle metabolism of sea-level natives following short-term high-altitude residence.

The influence of short-term high-altitude (HA) residence on intramuscular pH and skeletal muscle enzyme activity of sea-level (SL) residents was investigated. Vastus lateralis muscle samples were obtained by biopsy from rested subjects (n = 5) at SL (50 m) and on the 18th day of HA residence (4,300 m) for determination of glycogen phosphorylase, hexokinase, malate dehydrogenase, and total lactate dehydrogenase activities. A second group of subjects (n = 6) performed cycle exercise of the same absolute intensity (mean +/- SE = 195 +/- 5 W) at SL and on the 15th day of residence at HA. Before and immediately after exercise, vastus lateralis muscle samples were obtained for the determination of intramuscular pH, and venous blood was obtained for determination of lactate concentration. The first group of subjects showed no significant changes in skeletal muscle enzyme activity after 18 days at HA. The second group of subjects were instructed to exercise for exactly 30 min, and all but one could complete the entire bout at SL. However, at HA, none could continue 30 min, and time to exhaustion (mean +/- SE) was 11.9 +/- 1.6 min. Resting intramuscular pH was not significantly different after HA residence as compared to SL. The fall in intramuscular pH was less with exercise on day 15 at HA than during SL exercise. Likewise, the increase in blood lactate concentration with exercise at HA was less than at SL. These data indicate that, after 15-18 days of HA residence, limitations in exercise performance are not due to inordinate intramuscular acidosis or to changes in the activity of glycolytic and oxidative enzymes.

Adaptation, Physiological↗

PubMed1984

Effect of high intensity interval training on 2,3-diphosphoglycerate at rest and after maximal exercise.

The purpose of this study was to examine the effect of intense interval training on erythrocyte 2,3-diphosphoglycerate (2,3-DPG) levels at rest and after maximal exercise. Eight normal men, mean +/- SE = 24.2 +/- 4.3 years, trained 4 days X week-1 for a period of 8 weeks. Each training session consisted of eight maximal 30-s rides on a cycle ergometer, with 4 min active rest between rides . Prior to and after training the subjects performed a maximal 45-s ride on an isokinetic cycle ergometer at 90 rev X min-1 and a graded leg exercise test ( GLET ) to exhaustion on a cycle ergometer. Blood samples were obtained from an antecubital vein before, during and after the GLET only. Training elicited significant increases in the amount of work done during the 45-s ride (P less than 0.05), and also in maximal oxygen uptake (VO2 max: Pre = 4.01 +/- 0.13; Post = 4.29 +/- 0.07 1 X min-1; P less than 0.05) during exercise and total recovery VO2 (Pre = 19.14 +/- 0.09; Post = 21.45 +/- 0.10 1 X 30 min-1; P less than 0.05) after the GLET . After training blood lactate was higher, base excess lower and pH lower during and following the GLET (P less than 0.05 for all variables).(ABSTRACT TRUNCATED AT 250 WORDS)

2,3-Diphosphoglycerate↗

PubMed1984

Oxygen tension in antecubital blood of trained and untrained males after maximal leg exercise.

This study compared oxygen tension (pO2) and percent oxygen saturation (SO2) in antecubital venous blood of six untrained (UT) and six endurance trained (ET) males during and following a graded leg exercise test to exhaustion on a cycle ergometer. Mean (+/- SE) resting values for pO2 were 29.3 (+/- 2.3) and 30.3 (+/- 2.0) mmHg, and SO2 were 51.8 (+/- 5.2) and 54.9 (+/- 4.6)% for the ET and UT men, respectively. At exhaustion pO2 decreased to 23.0 (+/- 4.5) and 23.3 (+/- 4.7) mmHg, while SO2 decreased to 29.6 (+/- 9.7) and 31.3 (+/- 9.7)% for the ET and UT subjects, respectively. There were no significant differences between the two groups in either pO2 or SO2 at rest or during exercise. However, there were marked increases in pO2 and SO2 during the 5 min recovery period for both groups. The ET cyclists demonstrated significantly higher pO2 and SO2 levels than the UT group at each min of recovery; e.g., at 4 min postexercise pO2 was 72 and 49 mmHg for the ET and UT men, respectively (p less than 0.05). The general rise in pO2 and SO2 for both groups was attributed to an increased arterialization of the antecubital venous blood while postexercise hyperventilation may have also elevated pO2 values. The higher values for the ET subjects during recovery were explained by a lower peripheral sympathetic tone and a presumably greater cardiac output at exhaustion for the ET group than the UT group, which may have allowed a relatively greater distribution of arterialized blood to the periphery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1982

Muscle glycogen storage and its relationship with water.

This study examined the relationship between muscle glycogen and muscle water content. Exercise dietary manipulations were used to vary skeletal muscle glycogen levels in four groups of rodents: (1) eight animals were sedentary controls (SC); (2) ten animals were treadmill familiarized and allowed to recover 24 h before sacrifice (F); (3) ten animals were treadmill familiarized and exercised to exhaustion (E); (4) ten animals were treadmill familiarized, exercised to exhaustion, and allowed to recover with food and water ad libitum for 72 h (ER). All animals were sacrificed in a resting state to normalize intracellular, extracellular, and interstitial water compartments; thus, the E group was sacrificed 45 m in following their run. The treatments altered skeletal muscle glycogen to values ranging from 10.0 to 30.2 mumol glucosyl units/g wet tissue weight. Neither muscle triglyceride nor protein levels were affected by the treatments. Muscle water content expressed as mumol H2O lost/g wet tissue weight or made relative to protein content showed no consistent relationship to the glycogen content. These data, therefore, do not support the commonly accepted muscle glycogen-to-water ratio of 1.0:2.7 (g:g). Further work is necessary to quantify the exact amount of water that is actually associated with the glycogen complex.

Animals↗

PubMed1982

Determination of human muscle pH in needle-biopsy specimens.

The homogenate technique for the determination of muscle pH (pHm) has been studied to assess the influence of delayed freezing and the composition and volume of the homogenizing medium on human muscle pH at rest and after exhaustive exercise. It was concluded that resting muscle samples must be frozen within 2 s to prevent falsely high pHm values. Muscle specimens used for lactate determinations (HLam), on the other hand, can be delayed in freezing for up to 30 s without altering the HLam content. A 30- to 40-s delay in biopsying the muscle after the cessation of exhaustive exercise does not appear to alter pHm or HLam values. Although the homogenate method does not provide information relative to the status of selected muscle fibers, it does offer a reliable sensitive measure of mean changes in the acidification of muscle with intense exercise.

Biopsy, Needle↗

PubMed1982

Relationship between power and sprint freestyle swimming.

In an effort to determine the role played by power in sprint swimming, 40 competitive swimmers (22 females and 18 males) were tested for arm power at velocities ranging from 1.60-3.28 m . s-1 using an apparatus that was specifically designed to mimic the arm action during swimming. Measurements were also made to determine the contribution of fatigability to spring swimming performance. In addition, each swimmer performed a series of 25-yd (22.86 m) freestyle sprints. A close relationship was found between power output and sprint swimming performance (r = 0.90). The highest power recordings were obtained at test velocities of 2.05 and 2.66 m . s-1, with the average velocity required for peak power being 2.40 m . s-1. This point is referred to as the optimal velocity. Four detrained swimmers were tested before and after 4 wk of isokinetic strength training only. On the average, performance improved 3.76%, while arm power increased by 18.66%. The fatigability of the competitive swimmers was not related to their sprint ability (r = 0.01). It is concluded that power, as measured in this study, offers an objective assessment of a component essential for success in sprint swimming.

Adolescent↗