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Biomedical subjects

R J Robertson

Publications and source records attributed to R J Robertson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Regulating exercise intensity using ratings of perceived exertion during arm and leg ergometry.

The purpose of this investigation was to examine the validity of regulating exercise intensity using ratings of perceived exertion (RPEs) during arm crank and leg cycle exercise at 50 and 70% peak oxygen consumption (VO2peak). Ten men and seven women [26 (1) years old; mean (SE)] participated in this study. Each subject completed a maximal estimation trial and two submaximal exercise bouts (production trials) on both an arm and leg ergometer. During each maximal estimation trial, subjects were asked to give a RPE for each stage of the exercise. RPEs, heart rates (HR), and power outputs (PO) equivalent to 50 and 70% VO2peak for each exercise mode were then estimated from plots of RPE versus oxygen consumption (VO2), HR versus VO2, and PO versus VO2, respectively. During the submaximal trials, subjects were instructed to select workloads on an arm and leg ergometer that produced the previously estimated RPEs. Comparisons were made for VO2, HR, and PO between the estimation and production trials for each mode at each exercise intensity. HR did not differ between the trials at either 50 or 70% VO2peak during arm and leg ergometry. In addition, VO2 and PO did not differ between the trials at either 50 or 70% VO2peak during arm ergometry and at 50% VO2peak during leg ergometry. However, these two parameters were lower (P < 0.05) during the production trial [1.88 (0.15) l x min(-1) and 89.1 (10.1) W, respectively] as compared to the estimation trial [2.08(0.14) l x min(-1) and 102.4 (6.5)W, respectively] during leg ergometry at 70% VO2peak. In conclusion, using RPEs to regulate exercise intensity is physiologically valid during arm ergometry at both 50 and 70% VO2peak and during leg ergometry at 50% VO2peak. However, this prescriptive approach remains questionable during leg cycle exercise at 70% VO2peak.

Adult↗
PubMed1998

The comparative effects of sports massage, active recovery, and rest in promoting blood lactate clearance after supramaximal leg exercise.

OBJECTIVE: To determine the comparative effect of sports massage, active recovery, and rest on promoting blood lactate clearance after maximal anaerobic (supramaximal) leg exercise. DESIGN AND SETTING: A counterbalanced experimental design with repeated measures was used. The repeated measures were the three treatment conditions. The order of the conditions was determined by random assignment to a counterbalanced test sequence. All data were collected in the Human Energy Research Laboratory at the University of Pittsburgh. SUBJECTS: Ten male competitive cyclists volunteered for this investigation. MEASUREMENTS: Serial venous blood samples were drawn and analyzed for blood lactate concentration for each test condition. RESULTS: There were significant main effects for both absolute and relative values of blood lactate concentration between the three treatment groups and across time within groups. CONCLUSIONS: After supramaximal leg exercise, active recovery produced significant decreases in both absolute and relative measures of blood lactate concentration when compared with the sports massage and rest conditions. No significant difference was found between sports massage and rest for either absolute or relative changes in blood lactate concentration.

Journal Article↗
PubMed1997

Insulin and glucagon immunoreactivity during high-intensity exercise under opiate blockade.

Eight fit men [maximum oxygen consumption (VO2max) 64.6 (1.9) ml x kg(-1)xmin(-1), aged 28.3 (1.7) years (SE in parentheses) were studied during two treadmill exercise trials to determine the effect of endogenous opioids on insulin and glucagon immunoreactivity during intense exercise (80% VO2max). A double-blind experimental design was used with subjects undertaking the two exercise trials in counterbalanced order. Exercise trials were 20 min in duration and were conducted 7 days apart. One exercise trial was undertaken following administration of naloxone (N; 1.2 mg; 3 ml) and the other after receiving a placebo (P; 0.9% NaCl saline; 3 ml). Prior to each experimental trial a flexible catheter was placed into an antecubital vein and baseline blood samples were collected. Immediately after, each subject received either a N or P bolus injection. Blood samples were also collected after 20 min of continuous exercise (running). Glucagon was higher (P < 0.05), while insulin was lower (P < 0.05), during exercise compared with pre-exercise values in both trials. However, glucagon was higher (P < 0.05) in the P than in the N exercise trial [141.4 (8.3) ng x 1(-1) vs 127.2 (7.6) ng x 1(-1)]. There were no differences in insulin during exercise between the P and N trials [50.2 (4.3) pmol x 1(-1) vs 43.8 (5) pmol x 1(-1)]. These data suggest that endogenous opioids may augment the glucagon response during intense exercise.

Adult↗
PubMed1997

Metabolic efficiency during arm and leg exercise at the same relative intensities.

This study was conducted to compare gross efficiency (GE), net efficiency (NE), work efficiency (WE), and delta efficiency (DE) between arm crank and cycle exercise at the same relative intensities. Eight college-aged males underwent two experimental trials presented in a randomized counterbalanced order. During each trial subjects performed three intermittent 7-min exercise bouts separated by 10-min rest intervals on an arm or semirecumbent leg ergometer. The power outputs for the three bouts of arm crank or cycle exercise corresponded to 50, 60, and 70% of the mode-specific VO2peak. GE, NE, and WE were determined as the ratio of Kcal.min-1 equivalent of power output to Kcal.min-1 of total energy expended, energy expended above rest and energy expended above unloaded exercise, respectively. DE was determined as the ratio of the increment of Kcal.min-1 of power output above the previous lower intensity to the increment of kcal.min-1 of total energy expended above the previous lower intensity. GE and NE did not differ between arm crank and cycle exercises. However, WE was lower (P < 0.05) during arm crank than cycle exercise at 50, 60, and 70% VO2peak. DE was also lower (P < 0.05) during arm crank than cycle exercise at delta 50-60 and at delta 60-70% VO2peak. It is concluded metabolic efficiency as determined by work and delta efficiency indices was lower during arm crank compared with cycle exercise at the same relative intensities. These findings add to the understanding of the difference in metabolic efficiency between upper and lower body exercise.

Adult↗
PubMed1997

Acute effect of amino acid ingestion and resistance exercise on plasma growth hormone concentration in young men.

Sixteen men completed four trials at random as follows: (Trial A) performance of a single bout of resistance exercise preceded by placebo ingestion (vitamin C); (Trial B) ingestion of 1,500 mg L-arginine and 1,500 mg L-lysine, immediately followed by exercise as in Trial A; (Trial C) ingestion of amino acids as in Trial B and no exercise; (Trial D) placebo ingestion and no exercise. Growth hormone (GH) concentrations were higher at 30, 60, and 90 min during the exercise trials (A and B) compared with the resting trials (C and D) (p < .05). No differences were noted in [GH] between the exercise trials. [GH] was significantly elevated during resting conditions 60 min after amino acid ingestion compared with the placebo trial. It was concluded that ingestion of 1,500 mg arginine and 1,500 mg lysine immediately before resistance exercise does not alter exercise-induced changes in [GH] in young men. However, when the same amino acid mixture is ingested under basal conditions, the acute secretion of GH is increased.

Adult↗
PubMed1996

The effects of incremental submaximal exercise on circulating leukocytes in physically active and sedentary males and females.

To study the effects of exercise on circulating leukocytes and leukocyte subsets, physically active (n = 32) and sedentary (n = 32) male and female subjects were randomly assigned to an exercise or control condition. Exercise involved a continuous incremental protocol consisting of cycling for three periods of 6 min at power outputs corresponding to 55%, 70% and 85% maximal oxygen uptake (VO2max). Blood samples were drawn from a venous catheter at baseline, and at 6 min, 12 min, and 18 min after beginning the exercise and 2 h following completion of exercise. Resting- and exercise-induced alterations in total leukocytes were independent of gender and subject fitness level. Relative to baseline, each increment in workload resulted in a rapid increase in the number of circulating leukocytes. Increases in neutrophils, lymphocytes and monocytes accounted for the exercise-induced leukocytosis. With regard to lymphocytes, exercise resulted in a significant increase in the number of T cells (CD3+), T helper cells (CD4+), T suppresser (CD8+) and natural killer (NK) cells (CD3-/CD16+/CD56+). The largest percentage increase occurred in the NK cell population. The CD4+: CD8+ ratio decreased (P < 0.001) throughout exercise due to a larger increase in the number of CD8+ cells relative to CD4+ cells. An exercise-induced neutrophilia, lymphocytopenia, and eosinophelia was observed 2 h into recovery. Exercise resulted in significant increases in plasma epinephrine and norepinephrine levels. There was no indication of a hypothalamic-pituitarty-adrenal response during exercise. The results indicate that the rapid, albeit transient, alteration in the number of circulating leukocytes during and following an acute progressive incremental exercise test are independent of gender and fitness.

Adult↗
PubMed1996

Exercise-induced alterations in natural killer cell number and function.

To study the effects of exercise on natural killer (NK) cell number and activity (NKCA) healthy male (n = 32) and female (n = 32) subjects were randomly assigned to an exercise or control condition. Exercise involved a continuous incremental protocol consisting of cycling for three periods of 6 min at work rates corresponding to 55%, 70% and 85% peak oxygen uptake (VO2peak). Blood samples were drawn at baseline, at 6 min, 12 min and 18 min during exercise, and at 2 h following completion of exercise. Relative to both baseline and control conditions, exercise resulted in an increase in the number of circulating lymphocytes. The proportion of T cells (CD3+) and B cells (CD19+) significantly decreased, and NK cells (CD3-CD16+CD56+) increased throughout exercise. NKCA increased (P < 0.001) during the initial 6 min of exercise with no further changes observed, despite increases (P < 0.001) in the number and proportion of circulating NK cells during exercise at 70% and 85% VO2peak. Plasma epinephrine and norepinephrine increased (P < 0.001) above baseline at 12 min and 18 min. The changes in NK cell number and function were independent of gender. The results indicate that short-duration low-intensity exercise can significantly increase NK cell number and activity. However, alterations in NK cell number are not accompanied by changes of a similar magnitude in NKCA.

Adult↗
PubMed1996

Effects of exercise with varying energy expenditure on high-density lipoprotein-cholesterol.

To investigate the effect of varying energy expenditure on acute high-density lipoprotein-cholesterol (HDL-C) changes, 12 healthy endurance-trained men completed three- counterbalanced running trials at different energy expenditures: trial 1, 1690.3 (24.4) kJ [mean (SD)]; trial 2, 2529.1 (24.0) kJ; trial 3, 3384.3 (36.6) kJ, with exercise intensity at 75% of maximal oxygen consumption. For each trial, blood samples were collected at 24 h pre-exercise (24 h Pre), immediately post-exercise, 1 h post-exercise, 6 h post-exercise (6 h PE), and 24 h post-exercise (24 h PE). Plasma samples were analyzed for HDL-C, HDL2-C and HDL3-C subfractions, and triglycerides (TG). In addition, post-heparin plasma samples were analyzed at 24 h Pre, 6 h PE and 24 h PE for lipoprotein lipase activity (LPLA) and hepatic triglyceride lipase activity. All samples were corrected for plasma volume changes and compared to 24 h Pre (baseline). When trials were combined, an increase (P < 0.05) in HDL-C was observed 24 h PE, via an increase (P < 0.05) in HDL3-C. An increase (P < 0.05) in LPLA and decrease (P < 0.05) in TG at 24 h PE is suggested to be responsible for the increase in HDL3-C. In conclusion, no difference in HDL-C was observed among trials. However, when trials were combined, an increase in HDL-C was observed, suggesting that an energy expenditure of no greater than 3384 kJ is needed to promote favorable changes in HDL-C.

Adolescent↗
PubMed1996

Lymphocyte function and cytokine production during incremental exercise in active and sedentary males and females.

This study examined the effects of acute continuous incremental exercise on lymphocyte mitogenic function and cytokine production in physically active and sedentary males and females. Physically active (n = 32) and sedentary (N = 32) male and female subjects were randomly assigned to an exercise or control condition. Exercise involved a continuous incremental protocol consisting of cycling for 3 periods of 6 min at workrates corresponding to 55%, 70% and 85% VO2peak. Blood samples were drawn from a venous catheter at baseline, 6 min, 12 min and 18 min, and 2 h following completion of exercise. Relative to baseline and control condition the percentage of T (CD3+) and B cells (CD19+) significantly decreased, and the percentage of NK cells (CD3-CD16+CD56+) increased (p < 0.001) during each stage of the incremental exercise test. The proliferative response to ConA was suppressed, enhanced, or unchanged using 1.25 micrograms/ml, 2.5 micrograms/ml and 5.0 micrograms/ml ConA, respectively. The in-vitro production of IL-1 and IFN-gamma increased during each workload. In contrast IL-4 production did not change during exercise. The resting and exercise induced alterations in lymphocyte function and cytokine production were independent of gender and fitness level, and returned to baseline 2 h into recovery. The in-vitro production of IFN-gamma and IL-4 suggests that physical activity may alter the balance of TH1 and TH2 lymphocytes.

Adult↗
PubMed1996

The effects of acute exercise on gallbladder function in an adult female population.

It has been suggested that aerobic exercise influences gallstone disease pathogenesis through its effects on gallbladder motility. The purpose of the present investigation was to examine the effects of acute aerobic exercise on gallbladder emptying. Gallbladder function was evaluated, via cholescintigraphy, in 12 healthy females after undergoing two experimental trials [i.e., postprandial (P) and exercise + postprandial (E + P))]. In the E + P trial, 60 min after injection of 99mTc disofenin, subjects exercised for 30 min at 65.3 +/- 0.9%, (mean +/- SEM) of VO2 peak on a recumbent leg ergometer, and then ingested 8 oz of a liquid meal to promote gallbladder emptying. In the P trial the meal was administered at the same time relative to the E + P trial; however, for the 30 min prior to meal ingestion subjects remained in a resting supine position. Postprandial gallbladder ejection fraction (EF) was nonsignificantly higher in the E + P trial (49.4 +/- 5.1%) than in the P trial (46.6 +/- 6.7%). Results of this study also indicated that during a fasted state the gallbladder undergoes significant periods of spontaneous emptying both at rest EF = 25 +/- 5.6% (P < 0.02) and during exercise EF = 17 +/- 4.3% (P < 0.01). In conclusion, the results of this study indicate that 30 min of aerobic exercise at 65% of VO2 peak does not effect gallbladder motility in a healthy, premenopausal, female population.

Adult↗
PubMed1996

Effect of exercise intensity on glucose and insulin metabolism in obese individuals and obese NIDDM patients.

OBJECTIVE: The primary purpose of this study was to evaluate the acute effect of exercise of differing intensity on plasma glucose and insulin responses to an oral glucose challenge. RESEARCH DESIGN AND METHODS: Six obese men and six obese men with NIDDM of similar age, weight, percentage body fat, and VO2peak participated in the study. Each subject underwent two 7-day exercise programs in a counterbalanced order at 2-week intervals. During each 7-day exercise period, the subjects cycled every day at a power output corresponding to 50% VO2peak for 70 min or 70% VO2peak for 50 min. Muscle glycogen utilization was estimated during exercise on day 7 using a [3H]glucose infusion technique in conjunction with indirect calorimetry. During the day before and after each 7-day exercise period, a 3-h oral glucose tolerance test (OGTT) was administered after a 12-h overnight fast. RESULTS: The average caloric expenditure did not differ between exercise at 50 and 70% VO2peak in both obese and obese NIDDM subjects. However, the carbohydrate oxidation was higher (P < 0.05) during exercise at 70 than 50% VO2peak in obese subjects (77 +/- 5 vs. 68 +/- 6 g) and obese NIDDM subjects (70 +/- 4 vs. 58 +/- 6 g). Muscle glycogen utilization was also higher (P < 0.05) during exercise at 70 than 50% VO2peak in obese subjects (59 +/- 9 vs. 30 +/- 7 g) and in obese NIDDM subjects (48 +/- 5 vs. 24 +/- 5 g). In obese subjects, plasma glucose response area during the OGTT did not change after 7 days of exercise at either 50 or 70% VO2peak. Plasma insulin response area during the OGTT also did not change after 7 days of exercise at 50% VO2peak. However, plasma insulin response area was reduced (P < 0.05) after 7 days of exercise at 70% VO2peak (9,644 +/- 1,783 vs 7,538 +/- 1,522 microU.ml-1.180 min-1). In obese NIDDM subjects, both plasma glucose and insulin response areas during the OGTT did not decrease after 7 days of exercise at either 50 or 70% VO2peak. CONCLUSIONS: It is concluded that the exercise-induced improvement in insulin sensitivity is influenced by exercise intensity in obese individuals. The improved insulin sensitivity after 7 days of exercise at 70% VO2peak in obese individuals may be related to greater muscle glycogen utilization during exercise. The lack of improvement in glucose tolerance and insulin sensitivity after 7 days of exercise at either 50 or 70% VO2peak in obese NIDDM patients may be due to the fact that the NIDDM patients selected in the present study were relatively hypoinsulinemic.

Adipose Tissue↗
PubMed1996

A new method for prescribing exercise: three-point ratings of perceived exertion.

An accurate exercise prescription for ratings of perceived exertion has previously depended on data from a maximal graded exercise test during which RPE was measured. In many clinical settings RPE is not measured; in many fitness settings maximal testing is not feasible. A new method using treadmill speed or power output of a cycle ergometer at an RPE of 13 from a submaximal test which can be used in these situations is described. We evaluated the accuracy of this method at 50%, 60%, 70%, and 85% VO2max. A total of 160 target RPEs were developed using traditional procedures and the new method. No significant differences between RPEs obtained with the two techniques were found. The mean difference was less than one unit of RPE. It appears that the new method is valid for intensities of 50% to 85% VO2max and that data from either the cycle ergometer or the treadmill can be used to prepare exercise prescriptions.

Adult↗
PubMed1996

Effect of carbohydrate substrate availability on ratings of perceived exertion during prolonged exercise of moderate intensity.

This investigation examined the effect of carbohydrate substrate availability on ratings of perceived exertion (RPE) during cycling at moderate intensity to exhaustion and the relation between submaximal endurance performance and RPE obtained following 2 hr. of cycling at moderate intensity. Seven male cyclists performed two exercise trials at power output corresponding to 70% of their peak oxygen uptake until exhaustion. Subjects ingested either a 6% glucose/sucrose solution at the rate of 0.6 g.kg-1 (Body Weight).hr.-1 or an equal volume of artificially flavored placebo every 20 min. throughout the exercise trials. RPE for the legs, chest, and over-all body, and oxygen consumption, expired ventilation, carbohydrate oxidation rate, and blood concentrations of glucose, glycerol, and lactate were measured every 20 min. throughout exercise and at exercise termination. Statistical analysis of these dependent variables indicates that (1) an exercise-induced decrease in blood-borne carbohydrate substrate intensifies leg and over-all perceptions of exertion during the later stages of prolonged cycling at 70% VO2peak. (2) Factors other than availability of blood-borne carbohydrate substrate may influence perceptual intensity at exhaustion. (3) Ratings of perceived exertion for the legs and over-all body obtained after 2 hr. of cycling at moderate intensity may be useful in predicting submaximal endurance performance.

Attitude to Health↗
PubMed1996

American College of Sports Medicine position stand. The use of blood doping as an ergogenic aid.

Blood doping has been achieved by either infusing red blood cells or by administering the drug erythropoietin to artificially increase red blood cell mass. Blood doping can improve an athlete's ability to perform submaximal and maximal endurance exercise. In addition, blood doping can help reduce physiologic strain during exercise in the heat and perhaps at altitude. Conversely, blood doping is associated with risks that can be serious and impair athletic performance. These known risks are amplified by improper medical controls, as well as the interaction between dehydration with exercise and environmental stress. Finally, the medical risks associated with blood doping have been estimated from carefully controlled research studies, and the medically unsupervised use of blood doping will increase these risks. It is the position of the American College of Sports Medicine that any blood doping procedure used in an attempt to improve athletic performance is unethical, unfair, and exposes the athlete to unwarranted and potentially serious health risks.

Altitude↗
PubMed1995

Endogenous opioids may modulate catecholamine secretion during high intensity exercise.

To determine the effect of endogenous opioids on catecholamine response during intense exercise [80% maximal oxygen uptake (VO2max)], nine fit men [mean (SE) VO2max, 63.9 (1.7) ml.kg-1.min-1; age 27.6 (1.6) years] were studied during two treadmill exercise trials. A double-blind experimental design was used with subjects undertaking the two exercise trials in counterbalanced order. Exercise trials were 20 min in duration and were conducted 7 days apart. One exercise trial was undertaken following administration of naloxone (N; 1.2 mmol.l-1; 3 ml) and the other after receiving a placebo (P; 0.9% saline; 3 ml). Prior to each experimental trial a flexible catheter was placed into an antecubital vein and baseline blood samples were collected. Immediately afterwards, each subject received bolus injection of either N or P. Blood samples were also collected after 20 min of continuous exercise while running. Epinephrine and norepinephrine were higher (P < 0.05) in the N than P exercise trial with mean (SE) values of 1679 (196) versus 1196 (155) pmol.l-1 and 24 (2.2) versus 20 (1.7) nmol.l-1, respectively. Glucose and lactate were higher (P < 0.05) in the N than P exercise trial with values of 7 (0.37) versus 5.9 (0.31) mmol.l-1 and 6.9 (1.1) versus 5.3 (0.9) mmol.l-1 respectively. These data suggest an opioid inhibition in the release of catecholamines during intense exercise.

Adult↗
PubMed1995

Effect of carbohydrate ingestion subsequent to carbohydrate supercompensation on endurance performance.

This investigation determined whether carbohydrate ingestion during prolonged moderate-intensity exercise enhanced endurance performance when the exercise was preceded by carbohydrate supercompensation. Seven male trained cyclists performed two trials at an initial power output corresponding to 71 +/- 1% of their peak oxygen consumption. During the trials, subjects ingested either a 6% glucose/sucrose (C) solution or an equal volume of artificially flavored and sweetened placebo (P) every 20 min throughout exercise. Both C and P were preceded by a 6-day carbohydrate supercompensation procedure in which subjects undertook a depletion-taper exercise sequence in conjunction with a moderate- and high-carbohydrate diet regimen. Statistical analysis of time to exhaustion, plasma glucose concentration, carbohydrate oxidation rate, fat oxidation rate, and plasma glycerol concentration indicated that in spite of a carbohydrate supercompensation procedure administered prior to exercise, carbohydrate ingestion during exercise can exert an additional ergogenic effect by preventing a decline in blood glucose levels and maintaining carbohydrate oxidation during the later stages of moderate-intensity exercise.

Adult↗