Biomedical subjects

H A Quinney

Publications and source records attributed to H A Quinney.

At least 19 recordsLinked to original sources

PubMed1995

Validity of breathing frequency to monitor exercise intensity in trained cyclists.

This study compared breathing frequency (fB) during a ventilation threshold (VT) test with fB during a simulated 40 km time trial (40TT) to assess whether fB can be used to monitor exercise intensity. Twenty-six male cyclists (mean +/- SD VO2max = 4.42 +/- 0274 l.min-1) performed an incremental VT ergometer test and a simulated 40TT on a set of wind-loaded rollers. During the 40TT, expired gas was collected for 3 min using open circuit spirometry at 10 km intervals. A significant correlation (r = 0.89; p < or = 0.05) was found between the fB threshold (VTf) and the gas exchange VT (VTg) (3.42 +/- 0.08 and 3.31 +/- 0.09 l.min-1, respectively). No differences were found in VO2 at the VTf vs. X VO2 (3.48 +/- 0.08 l.min-1) during the simulated 40TT. However, when fB in br.min-1 calculated from the VT test (32.5 br.min-1), was compared with fB during the 40TT (45.6 br.min-1), there was a significant difference. Ventilation, heart rate and the respiratory exchange ratio were all significantly higher during the 40TT. Although a significant relationship was found between the VT test and the 40TT for VTf measured in l.min-1 of VO2 (r = 0.66; p < or = 0.05), fB in br.min-1 obtained from the incremental test should not be used to identify exercise training intensity. These data suggest that during competition, trained athletes exercise at a higher fB than that determined when being tested, implying that fB in br.min-1 may not be a valid measurement of exercise intensity.

Adult↗

PubMed1995

Parallel insulin-like growth factor I and insulin resistance in muscles of rats fed a high fat diet.

The possibility of a similarity between insulin-like growth factor-I (IGF-I) and insulin resistance in epitrochlearis muscles of rats fed a high fat diet [20% (wt/wt) fat] vs. a low fat diet [5% (wt/wt) fat] was investigated. Half-maximally and maximally effective concentrations of IGF-I- and insulin-stimulated 3-O-methyl-glucose transport were 2.32 and 25 nM, respectively, for IGF-I, compared with 0.79 and 20 nM for insulin. The high fat diet reduced both responsiveness and sensitivity of IGF-I-stimulated 3-O-methyl-glucose transport in parallel with the impaired insulin-stimulated 3-O-methyl-glucose transport. IGF-I binding at 2.5 nM to incubated epitrochlearis muscle was also decreased by the high fat diet (P < 0.05). Thus, the high fat diet caused simultaneous IGF-I and insulin resistance in rat skeletal muscle. The IGF-I resistance induced by feeding the high fat diet seems at least partially due to a reduction in IGF-I binding.

3-O-Methylglucose↗

PubMed1995

Knee muscle strength in elite male gymnasts.

This study was launched to establish the profile of knee dynamic concentric strength in elite male gymnasts after it was found that three of the 10-member Canadian men's gymnastics team had incurred anterior cruciate ligament (ACL) rupture. The dynamic concentric force characteristics of the quadriceps and hamstring muscles of 84 male gymnasts were studied at the Canadian National Championships using a Kin-Com isokinetic dynamometer. These tests were performed at 90 degrees/sec and 230 degrees/sec and revealed that the hamstrings to quadriceps peak torque ratio was not only unusually low (0.5) when compared with data collected in previous research, but that this ratio was consistent across all ages, from 12 to 27 years. The torque ratios were also reported at 30 degrees, 45 degrees, and 60 degrees and it was found that the ratios decreased as the joint angle increased and again was consistent across the four age groups. It was also found that the hamstrings to quadriceps peak torque ratio did not increase (hamstrings becoming stronger relative to quadriceps) as velocity of movement increased as has been reported in other studies. It was hypothesized that the large shear forces that are generated about the knee in gymnastics (extrinsically from backward landing and intrinsically from the quadriceps eccentrically contracting), combined with the relatively weak hamstrings, could be one cause for the increasing incidence of ACL injuries in that sport. The results of this study indicate that it would be prudent for clinicians involved with gymnasts to test for knee strength imbalance and to prescribe exercises to correct it when necessary.

Adolescent↗

PubMed1995

L-carnitine increases glucose metabolism and mechanical function following ischaemia in diabetic rat heart.

OBJECTIVE: Stimulation of glucose oxidation by L-carnitine improves mechanical recovery of ischaemic hearts from non-diabetic rats perfused with high levels of fatty acids. The aim of this study was to determine whether L-carnitine also increases glucose oxidation and function in diabetic rat hearts, which have suppressed glucose metabolism. METHODS: Isolated working hearts from six week streptozotocin diabetic and control rats were perfused with 11 mM (5-3H/U-14C)-glucose, 1.2 mM palmitate. Hearts were paced at 260 beats.min-1 during 60 min of low flow ischaemia, and were then subjected to 30 min of aerobic reperfusion. Total myocardial carnitine content in these hearts was first increased by a 60 min aerobic perfusion with 10 mM L-carnitine. RESULTS: Steady state glucose oxidation rates (measured as 14CO2 production) were depressed in diabetic rat hearts compared to control hearts during the initial aerobic period. However, L-carnitine treatment dramatically increased glucose oxidation rates in the diabetic rat hearts, as well as in control hearts. Glycolysis was also lower in diabetic rat hearts compared to control hearts, although L-carnitine treatment significantly increased glycolysis only in the diabetic animals. During reperfusion, steady state rates of glucose oxidation and glycolysis returned to preischaemic values in both the control and diabetic groups. L-carnitine treatment stimulated glucose oxidation during reperfusion in control and diabetic rat hearts. Mechanical function of control hearts returned to 38(SEM 9)% of preischaemic values, whereas in L-carnitine treated hearts function returned to 90(7)% of preischaemic values. Recovery of function was 80(15)% of preischaemic in the diabetic rat hearts, and was increased to 100% of preischaemic function with L-carnitine. CONCLUSIONS: Carnitine improves recovery of function of ischaemic non-diabetic rats by stimulating glucose oxidation during reperfusion, whereas it may be beneficial in diabetic rat hearts by stimulating both glycolysis during ischaemia and glucose oxidation during reperfusion.

Animals↗

PubMed1994

Dietary omega-3 and polyunsaturated fatty acids modify fatty acyl composition and insulin binding in skeletal-muscle sarcolemma.

Feeding animals with diets high in saturated fat induces insulin resistance, and replacing saturated fat isocalorically with poly-unsaturated fat, especially long-chain omega-3 fatty acids, will prevent the development of insulin resistance in skeletal-muscle tissue. To investigate the mechanism, rats were fed on high-fat (20%, w/w) semipurified diets for 6 weeks. Diets containing ratios of polyunsaturated/saturated (P/S) fatty acid of 0.25 (low-P/S diet) and 1.0 (high-P/S diet) were used to study the effect of the level of saturated fat. To study the effects of omega-3 fatty acids, diets with a low-P/S ratio containing either 0 (low-omega-3 diet) or 3.3% (high-omega-3 diet) long-chain omega-3 fatty acids from fish oil were fed. Plasma membrane from skeletal muscle was purified. The content of fatty acids in sarcolemmal phospholipid was significantly related to the dietary composition. Insulin binding to intact sarcolemmal vesicles prepared from rats fed on diets high in omega-3 fatty acids increased 14-fold compared with animals fed on the low-omega-3 diet (P < 0.0001). Feeding rats on a diet with a high P/S ratio increased sarcolemmal insulin binding by 2.3-fold (P < 0.05). Increased insulin binding was due to increased receptor number at the low-affinity high-capacity binding site. Dietary effects on insulin binding were eliminated when studies were carried out on detergent-solubilized membranes, indicating the importance of the phospholipid fatty acyl composition for insulin binding. The results suggest that dietary omega-3 and polyunsaturated fatty acids increase insulin binding to sarcolemma by changing the fatty acyl composition of phospholipid surrounding the insulin receptor, and this might be the mechanism by which dietary fatty acids modify insulin action.

Animals↗

PubMed1993

Proprioceptive sensibility in women with normal and osteoarthritic knee joints.

The objective of this study was to quantify the effect of degenerative joint change on the proprioceptive acuity of women with osteoarthritis (OA) of the knee. Middle-aged women with OA of the knee, age-matched healthy women, and younger healthy women were studied. Tests examined the ability of subjects to correctly reproduce knee angles in weightbearing and non-weightbearing situations. The knee angles were photographed and measured in degrees. The absolute error (AE) of each matching test was calculated and the mean AE of two tests was used as the criterion variable in a three-way analysis of variance (ANOVA). The relationship between the reproduction error and the osteoarthritic subjects' self-paced walking speed was also examined. Under both test conditions the AE of the osteoarthritic subjects was greater than that of the healthy subjects (p < .05). There was, however, no significant relationship between the AE measurements of the patients and their walking speed. These data indicate that while women with OA may have poorer proprioception than healthy controls, this impairment may not affect their walking ability.

Adult↗

PubMed1993

Maintenance of strength gains while performing endurance training in oarswomen.

This study investigated the retention of strength gained after resistance training, while performing aerobic endurance training. Following a 10-week resistance training program (three times a week) that included maintenance aerobic endurance training (twice a week), 18 varsity oarswomen were matched on strength and randomly assigned to two groups: Group 1 performed maintenance resistance training once a week and Group 2 performed resistance training twice a week. Both groups performed endurance training four times a week during the 6-week maintenance resistance training program. There was a significant increase in strength (multiple-RM test) for three upper and three lower body exercises after the initial 10-week resistance training program. A further significant increase in two exercises (inclined leg press and knee flexion) were observed after 6 weeks of maintenance resistance training and endurance training in both groups. No further significant increases were observed in the four other exercises during maintenance strength training. These latter findings occurred at the same time that VO2max and ventilation threshold increased. These results suggest that strength gains can be maintained with resistance training once or twice a week while focusing on improving aerobic endurance performance without compromising the latter.

Adult↗

PubMed1993

Beneficial effect of carnitine on mechanical recovery of rat hearts reperfused after a transient period of global ischemia is accompanied by a stimulation of glucose oxidation.

BACKGROUND: We have previously shown that increasing myocardial carnitine levels in fatty acid-perfused isolated working rat hearts dramatically increases glucose oxidation rates. Since high levels of fatty acids depress reperfusion recovery of ischemic hearts by inhibiting glucose oxidation, we determined what effect carnitine has on glucose oxidation during reperfusion of ischemic hearts. METHODS AND RESULTS: Isolated working rat hearts were perfused with 11 mM [5-3H/ul-14C]glucose, 1.2 mM palmitate, and 100 microU/ml insulin and subjected to a 35-minute period of global ischemia followed by aerobic reperfusion. Rates of glycolysis and glucose oxidation were determined by measuring tritiated water and 14CO2 production, respectively. Before ischemia, myocardial carnitine content was first increased by perfusing hearts during a 60-minute baseline aerobic perfusion with 10 mM L-carnitine. This resulted in a significant increase in total myocardial carnitine from 4,804 +/- 358 to 9,692 +/- 2,090 nmol/g dry wt (mean +/- SD). Glycolysis rates in carnitine-treated hearts were not significantly altered compared with control hearts during the aerobic perfusion (2,482 +/- 1,173 versus 1,840 +/- 1,365 nmol glucose.g dry wt-1 x min-1, respectively). In contrast, glucose oxidation rates in carnitine-treated hearts were significantly increased before ischemia compared with control hearts (471 +/- 209 versus 158 +/- 75 nmol glucose.g dry wt-1 x min-1, respectively). During reperfusion of previously ischemic hearts, glycolytic rates returned to preischemic values in both carnitine-treated and control hearts. Glucose oxidation rates also recovered to preischemic values in these hearts and remained significantly elevated in carnitine-treated hearts compared with control hearts (283 +/- 113 versus 130 +/- 27 nmol glucose.g dry wt-1 x min-1, respectively). Mechanical recovery in control hearts returned to 44% of preischemic values (measured as heart rate-peak systolic pressure product), whereas in carnitine-treated hearts, mechanical recovery returned to 71% of preischemic values. CONCLUSIONS: These results suggest that the beneficial effects of carnitine in the ischemic heart can be explained by the actions of this compound on overcoming fatty acid inhibition of glucose oxidation.

Acyl Coenzyme A↗

PubMed1993

Effect of fatiguing maximal isokinetic quadriceps contractions on ability to estimate knee-position.

This randomized controlled study compared the accuracy of knee positioning by 8 women after fatiguing maximal isokinetic contractions of the quadriceps with those of 8 controls who performed no exercise. The mean algebraic error (AE) and variable error (VE) showed a significant posttest improvement for the control group after a 5-min, intertrial period. There was no change in accuracy of knee positioning postexercise, however, for the experimental group. These findings suggest that, while a single bout of fatiguing knee exercises may not alter absolute accuracy of knee positioning, the movements may undermine the relative proficiency attainable by learning. They suggest a role for central as well as peripheral mechanisms in mediating this sensory modality.

Adolescent↗

PubMed1992

Carnitine stimulation of glucose oxidation in the fatty acid perfused isolated working rat heart.

The effects of L-carnitine on myocardial glycolysis, glucose oxidation, and palmitate oxidation were determined in isolated working rat hearts. Hearts were perfused under aerobic conditions with perfusate containing either 11 mM [2-3H/U-14C]glucose in the presence or absence of 1.2 mM palmitate or 11 mM glucose and 1.2 mM [1-14C]palmitate. Myocardial carnitine levels were elevated by perfusing hearts with 10 mM L-carnitine. A 60-min perfusion period resulted in significant increases in total myocardial carnitine from 4376 +/- 211 to 9496 +/- 473 nmol/g dry weight. Glycolysis (measured as 3H2O production) was unchanged in carnitine-treated hearts perfused in the absence of fatty acids (4418 +/- 300 versus 4547 +/- 600 nmol glucose/g dry weight.min). If 1.2 mM palmitate was present in the perfusate, glycolysis decreased almost 2-fold compared with hearts perfused in the absence of fatty acids. In carnitine-treated hearts this drop in glycolysis did not occur (glycolytic rates were 2911 +/- 231 to 4629 +/- 460 nmol glucose/g dry weight.min, in control and carnitine-treated hearts, respectively. Compared with control hearts, glucose oxidation rates (measured as 14CO2 production from [U-14C]glucose) were unaltered in carnitine-treated hearts perfused in the absence of fatty acids (1819 +/- 169 versus 2026 +/- 171 nmol glucose/g dry weight.min, respectively). In the presence of 1.2 mM palmitate, glucose oxidation decreased dramatically in control hearts (11-fold). In carnitine-treated hearts, however, glucose oxidation was significantly greater than control hearts under these conditions (158 +/- 21 to 454 +/- 85 nmol glucose/g dry weight.min, in control and carnitine-treated hearts, respectively). Palmitate oxidation rates (measured as 14CO2 production from [1-14C]palmitate) decreased in the carnitine-treated hearts from 728 +/- 61 to 572 +/- 111 nmol palmitate/g dry weight.min. This probably occurred secondary to an increase in overall ATP production from glucose oxidation (from 5.4 to 14.5% of steady state myocardial ATP production). The results reported in this study provide direct evidence that carnitine can stimulate glucose oxidation in the intact fatty acid perfused heart. This probably occurs secondary to facilitating the intramitochondrial transfer of acetyl groups from acetyl-CoA to acetylcarnitine, thereby relieving inhibition of the pyruvate dehydrogenase complex.

Acyl Coenzyme A↗

PubMed1992

31P NMR of electrically stimulated rectus femoris muscle: an in vivo graded exercise model.

This study reports on the development of a model for studying skeletal muscle metabolism in humans using NMR spectroscopy. Graded exercise was simulated using electrical stimulation in 10 healthy, fit subjects (mean VO2max = 53 +/- 4 ml.kg-1.min-1). The effects of varying the stimulation parameters, namely, the stimulation frequency, the stimulation intensity, and the duty cycle, as well as the spectral interrogation volume, were compared using data acquired from the rectus femoris muscle. With stimulation, the inorganic phosphate to phosphocreatine concentration ratio ([P(i)]/[PCr]) and the intracellular pH both follow curvilinear relationships over the stimulation frequencies from 3 to 30 Hz, with the magnitude of the observed change related closely to stimulation intensity and duty cycle. Oxidative phosphorylation predominates at stimulation frequencies below 12 Hz, while anaerobic metabolism increases sharply above 12 Hz. Our findings show clearly the interdependence of the effects of the various stimulation parameters and emphasize the care that must be exercised in interpreting the physiological significance of the biochemical data obtained from electrical stimulation models used to study skeletal muscle metabolism.

Adult↗

PubMed1992

The effects of a reduced exercise duration taper programme on performance and muscle enzymes of endurance cyclists.

The influence of tapering on the metabolic and performance parameters in endurance cyclists was investigated. Cyclists (n = 25) trained 5 days.week-1, 60 min.day-1, at 75-85% maximal oxygen consumption (VO2max) for 8 weeks and were then randomly assigned to a taper group: 4D (4 days; n = 7), 8D (8 days; n = 6), CON (control, 4 days rest; n = 6), NOTAPER (non-taper, continued training; n = 6). Muscle biopsy specimens taken before and after training and tapering were analysed for carnitine palmityltransferase (CPT), citrate synthase, beta-hydroxyacyl CoA dehydrogenase (HOAD), cytochrome oxidase (CYTOX), lactate dehydrogenase, glycogen and protein. Significant increases in VO2max (6%), a 60-min endurance cycle test (34.5%), oxidative enzymes (77-178%), glycogen (35%) and protein (34%) occurred following training. After the taper, HOAD and CPT decreased 25% (P less than 0.05) and 26% respectively, in the CON. Post-taper CYTOX values were different (P less than 0.05) for 4D and 8D compared with CON. Muscle glycogen levels were increased (P less than 0.05) after tapering in the 4D, 8D and CON, but decreased in NOTAPER. Similarly, power output at ventilation threshold was significantly increased in the 4D (27.4 W) and 8D (27 W) groups, but decreased (22 W) in the NOTAPER. These findings suggest that tapering elicited a physiological adaptation by altering oxidative enzymes and muscle glycogen levels. Such an adaptation may influence endurance cycling during a laboratory performance test.

Adult↗

PubMed1992

Acute insulin withdrawal from diabetic BB rats decreases myocardial glycolysis during low-flow ischemia.

We have previously demonstrated that withdrawal of insulin treatment from BB diabetic rats for a 24-hour period will increase the failure rate of hearts subjected to low-flow ischemia. The purpose of this study was to determine if this increased severity of ischemia was related to a decrease in glycolytic rates during ischemia. Two groups of insulin-dependent diabetic BB Wistar rats were used; in one group, insulin treatment was withheld from rats 24 hours prior to study (uncontrolled), while in the second group, the daily insulin injection was not withheld (insulin-treated). Isolated working hearts obtained from these animals were perfused with 30 mmol/L (2-3H/U-14C)-glucose and 1.2 mmol/L palmitate, at an 11.5 mm Hg left atrial preload and 80 mm Hg aortic afterload. Hearts were subjected to a 15-minute aerobic perfusion followed by 60 minutes of low-flow ischemia (coronary flow, 0.5 mL/min). Under aerobic conditions, steady-state glucose oxidation rates (measured as 14CO2 production) were decreased in the uncontrolled group compared with the insulin-treated group (85.3 +/- 21.5 v 406.2 +/- 120.1 nmol/min/g dry weight, respectively; P less than .05). Steady-state glycolytic rates (measured as 3H2O production) were also decreased in the uncontrolled group compared with the insulin-treated group (1.73 +/- 0.30 v 5.57 +/- 1.26 mumol/min/g dry weight, respectively; P less than .05). During low-flow ischemia, glucose-oxidation rates markedly decreased in both groups (23.9 +/- 8.7 and 38.3 +/- 25.2 nmol/min/g dry weight in the uncontrolled and insulin-treated diabetic rats, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1992

Effect of high velocity resistance training on peak torque, cross sectional area and myofibrillar ATPase activity.

The purpose of this investigation was to determine the effect of high velocity resistance (HVR) training on peak torque (PT), cross sectional area (CSA) and myofibrillar ATPase activity of the knee extensors. HVR training was performed in a circuit on hydraulic exercise equipment, 4 times a week for 5 weeks at an angular velocity of approximately 3.14 rad.s-1. Knee extension PT was determined on a Cybex II isokinetic dynamometer and CSA of the quadriceps femoris muscle was assessed using computer tomography (CT) scanning. Muscle biopsies were obtained from the lateral quadriceps muscle and were analyzed for myofibrillar ATPase activity. Knee extension peak torque was significantly increased at 1.57, 2.09, 3.14, 3.66 and 4.19 rad.s-1. Myofibrillar ATPase activity and CSA was also significantly increased after HVR training. These findings showed that short-term high velocity resistance training enhances the in vivo torque/velocity curve especially at fast angular velocities and these changes are partly attributed to an increase in muscle CSA and activity of myofibrillar ATPase.

Adaptation, Physiological↗

PubMed1992

Changes in blood pressure and cardiac output during maximal isokinetic exercise.

This study was undertaken to determine the blood pressure (BP) and cardiac output (Qc) responses to maximal isokinetic exercise. The subjects (n = 5) performed unilateral knee extension/flexion exercise (knee exercise) and unilateral elbow extension/flexion exercise (elbow exercise) at 0.52, 1.57, and 2.62 rads.sec-1. The BP was monitored using a cannula placed in the radial artery. Heart rate (HR), stroke volume (SV), and Qc were measured by impedance cardiography. In response to isokinetic exercise, HR and Qc increased significantly (p less than .01), while the SV did not. The BP response was characterized by significant increases in systolic, diastolic, and mean arterial pressure (MAP) (p less than .01). The Qc and MAP, responses were not influenced by the exercise velocity. The adjustments in HR, MAP, and rate pressure product (RPP) to the elbow exercise were qualitatively similar to those seen during the knee exercise, but the absolute values achieved were smaller (p less than .05). Compared with maximal dynamic exercise, the HR and SV responses to the knee exercises were lower. The MAP response to isokinetic exercise equaled the highest value achieved during dynamic exercise. Findings from the present study suggest that the cardiovascular stress (the increase in HR, MAP, and RPP) associated with isokinetic exercise is independent of the velocity of movement and is proportional to the active muscle mass.

Adult↗

PubMed1991

Physiological adaptations to concurrent endurance training and low velocity resistance training.

This study investigated the effects of concurrent endurances and low velocity resistance training (LVR) on measures of strength and aerobic endurance. One group (ES) performed concurrent endurance training 3 days a week and LVR training on alternate days, 3 days a week for 12 weeks. The other group (S) performed only LVR training 3 days a week for 12 weeks without any endurance training. Measurements and increases in training volume were made every three weeks in both groups. Group ES exhibited increases in submaximal exercise responses after 3, 9 and 12 weeks (p less than 0.05). Knee extension peak torque and total work as well as cross-sectional area of quadriceps femoris were significantly increased after 6 and 9 weeks of training in both groups. These findings indicate that no significant differences in strength gains were observed between subjects performing concurrent endurance and resistance training or resistance training only. However, the time-course of adaptations between groups was somewhat different.

Adaptation, Physiological↗

PubMed1991

Adaptations to endurance and low velocity resistance training performed in a sequence.

The purpose of this study was to examine the effects of two different sequences of the same two training programs on strength and endurance adaptations. One group completed 5 weeks of low velocity resistance (LVR) training prior to 5 weeks of endurance training (Group SE) while the other group (ES) completed the opposite sequence. Endurance training and resistance training resulted in anticipated increases in aerobic endurance measures and strength, respectively, regardless of the sequence followed. Some maintenance of strength was observed during subsequent endurance training in Group SE. However, the improvements in peak VO2 and submaximal exercise responses that occurred after endurance training in Group ES were not maintained with subsequent LVR training. This investigation suggests that conducting LVR training prior to endurance training may be more beneficial if resistance and endurance training are performed in a sequence.

Adult↗

PubMed1991

Time-motion analysis of and heart rate responses to amateur ice hockey officiating.

The physical activity of referees (n = 4) and linesmen (n = 6) was analyzed from videotapes of four varsity hockey games to determine the frequency, average duration, and total time spent in each of six activity categories. The average duration of activity was low while frequency of occurrence was high. Low intensity activities occupied 96% of total time for referees and 94% of time for linesmen. Heart rate responses were recorded every 5 seconds and synchronized to the videotapes for all referees and 5 linesmen. Heart rates were above 70% of maximum for 70% of the total ice time, which was greater than expected for the observed physical activity. Psychological stress during the course of a varsity hockey game could contribute to the high heart rate responses. It is concluded that training to increase aerobic fitness is an important aspect of ice hockey officiating to increase resistance to fatigue and aid in stress management.

Alberta↗