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Biomedical subjects

M J Plyley

Publications and source records attributed to M J Plyley.

At least 37 records · Page 2Linked to original sources
PubMed1991

Fiber type morphometry and capillary geometry in free, vascularized muscle transfers.

In order to establish the relationship among intraoperative ischemia time, the recovery of contractile function, muscle fiber morphometry, and capillary geometry following free muscle transfer, 15 male dogs underwent unilateral, orthotopic free transfer of the left gracilis muscle with microneurovascular anastomosis. Intraoperative ischemia time varied from 0 to 4 hours. After a recovery period averaging 14 months, isometric contractile function was measured in the transfers and the contralateral, control muscles. Muscle fiber type composition, fiber size, and capillary geometry were quantified from histochemical sections. Transferred and control muscles had similar type I fiber percentages, type I fiber sizes, and capillary densities. Type II fiber sizes were reduced in transfers relative to controls. There was no significant effect of intraoperative ischemia on any morphometric variable. Although contractile function was generally reduced after free, vascularized transfer, there was only a weak correlation between the recovery of tetanic tension and type I fiber percentage (r = 0.53, P less than 0.05). It is concluded that free, vascularized muscle transfer results in minimal disturbance of muscle fiber type composition, fiber size, or capillary supply and that the diminished contractile function observed in this setting is still largely unexplained.

Analysis of Variance↗
PubMed1991

Gains of cardiorespiratory fitness with arm-crank training in spinally disabled men.

Cardiorespiratory responses to four patterns of arm-crank training (thrice weekly sessions at 50 or 70% of peak oxygen intake, 20 or 40 min per session) were examined over 8, 16, and 24 weeks in 24 initially inactive subjects with paraplegia. Training was associated with a significant increment of the peak oxygen intake during arm-crank tests except in control subjects and those combining a low intensity (50% of peak) with short-duration training (20-min sessions). There were associated increases in cardiac stroke volume, as assessed by a carbon dioxide rebreathing technique during submaximal exercise. It is suggested that the performance of inactive wheelchair users is limited by a pooling of blood in paralysed regions, with a reduction of cardiac preloading; nevertheless, substantial gains of performance are possible through prolonged arm-crank exercise of moderate intensity.

Adolescent↗
PubMed1991

Left ventricular functional response to moderate and intense exercise.

The left ventricular (LV) volume and ejection fraction (EF) response to upright exercise was assessed on 15 normal subjects during cycle ergometry. Measures of cardiac function and gas exchange were made at rest, at 85% of the ventilatory anaerobic threshold (VAT; WL1), and at peak exercise (WL2). EF increased from rest (58 +/- 12%) during WL1 (66 +/- 10%), reaching significantly higher values at WL2 (69 +/- 8%; p less than .05). End-diastolic volume increased from rest during WL1 (136 +/- 36 ml vs. 118 +/- 32 ml; p less than .05), becoming significantly higher than rest during WL2 (141 +/- 41 ml). End-systolic volume was unchanged from rest (51 +/- 25 ml) during submaximal exercise (50 +/- 20 ml), but it decreased significantly during WL2 (44 +/- 21 ml; p less than .05). The systolic pressure/end-systolic volume ratio increased from 3.0 +/- 1.7 (rest) to 5.8 +/- 3.0 at WL2 (p less than .05). These results suggest that the Frank-Starling mechanism is operative throughout exercise, particularly during exercise below the VAT. LV performance after the VAT is further augmented by increased contractility with continued, yet diminished, utilization of the Frank-Starling mechanism.

Adult↗
PubMed1990

Skeletal muscle fiber type, fiber size, and capillary supply in elite soccer players.

This study determined the fiber type composition, the fiber size, and the capillary characteristics of the vastus lateralis muscle in 11 young, elite, male soccer players and 8 sedentary male, age-matched controls. There were no significant differences (P less than 0.05) in the fiber type percentages and fiber diameter between the soccer players and controls; however, all fiber types tended to be larger in the soccer players. The soccer players possessed a greater capillary supply; this was characterized by a significantly greater mean number of capillaries surrounding each fiber (5.7 +/- 0.9 vs. 4.9 +/- 0.4), a significantly larger capillary density (282.7 +/- 42.0 vs. 220.8 +/- 38.1), and a significantly higher capillary to fiber ratio (2.2 +/- 0.6 vs 1.7 +/- 0.1). The results indicate that soccer may be an appropriate stimulus for simultaneous adaptation to endurance and high intensity exercise.

Adult↗
PubMed1990

Moderate exercise and hemodilution during sleep deprivation.

The effect of 52 h of sleep deprivation (SD) upon blood constituents was studied in 12 young women aged 21.5 +/- 0.4 years. Subjects were individually isolated without time cues, performing a sequence of cognitive tasks. Significant decreases in hematocrit (p less than 0.002) and red cell count (p less than 0.04) developed, mainly over the first 28 h of SD, reaching a subsequent plateau or partial recovery. The calculated plasma volume also increased by 10.7 +/- 3.1% at 52 h, with recovery to a 6.9 +/- 3.2% increase the following day. About 1 L of water was retained over the first 30 h of SD, with a subsequent partial elimination of this excess. Plasma albumin and total protein concentrations were largely sustained in the face of the plasma expansion. The plasma pH showed a progressive fall from a baseline value of 7.381 +/- 0.014 to 7.332 +/- 0.006 at 52 h, while plasma bicarbonate decreased from a baseline figure of 31.2 +/- 0.7 to 26-27 mM/L (p less than 0.05). After 8 weeks, all subjects repeated the experiment, with the introduction of 30 min of exercise in the 40th h of wakefulness. Hematocrit and plasma volume changes were similar to those of the first experiment up to the time of exercise, but hematocrit decreased and plasma volume increased after the exercise bout, rather than reaching a plateau. Plasma pH increased with exercise, but returned to the previous low level at 52 h. Any arousing effect of the exercise bout was transient. The plasma expansion reflects metabolic and/or respiratory acidosis, plus possible effects of a prolonged period without recumbency.

Adult↗
PubMed1989

Isometric contractile function recovery following tourniquet ischemia.

The purpose of this study was to document the recovery of isometric contractile function following tourniquet ischemia. Male Wistar rats (N = 27) were subjected to unilateral hindlimb tourniquet ischemia of 0 hr (control, N = 6), 1 hr (N = 5), 2 hr (N = 5), 3 hr (N = 5) and 4 hr (N = 3). Following a 2-week recovery period, isometric force measurements were made from both gastrocnemii of each rat with the contralateral limb acting as the control side. Each muscle was analyzed for maximal twitch (Pt, N/g), maximal rate of rise of twitch tension (DP/dt, N/sec), time to peak tension (TPT, msec), half relaxation time (RT 1/2, msec), maximal tetanus (P0, N/g, at 100 Hz), and fatigue (Burke Fatigue Protocol). Pt, P0, and DP/dt were significantly different from control values (P less than 0.05) for all hours of tourniquet ischemia. A strong negative correlation (P less than 0.001) was found for twitch (R = -0.84), tetanus (R = -0.78), and maximal rate of force development (R = -0.83) with respect to increasing hours of ischemia. The recovery of isometric twitch and tetanic function following tourniquet ischemia is inversely related to the ischemic interval. This study quantified the relationship between muscle ischemia and recovery of function following a 2-week interval and stresses the functional physiological changes which occur in skeletal muscle following tourniquet ischemia.

Animals↗
PubMed1989

Extreme endurance training and fiber type adaptation in rat diaphragm.

Extreme endurance training was used to investigate the adaptability of the rat diaphragm muscle fibers. During the final phase of the 14-wk training program, the animals were running for 240 min/day at an estimated requirement of 80% of pretraining maximal O2 consumption. Analysis of a sample of the costal diaphragm indicated that training resulted in a 34% reduction (P less than 0.05) in the percent distribution of type IIa fibers [27.7 +/- 1.1 vs. 18.3 +/- 2.6 (SE)] and a 15% increase (P less than 0.05) in the percent of type IIb fibers (40.0 +/- 1.2 vs. 46.1 +/- 2.4). No change (P greater than 0.05) was found in the distribution of the type I fibers (32.3 +/- 1.2 vs. 35.7 +/- 1.3). Oxidative potential as assessed with NADH-tetrazolium reductase and measured microphotometrically increased (P less than 0.05) by 19% in type I fibers but did not change in either the type IIa or type IIb fibers. No effect of training was found when a different oxidative marker, succinic dehydrogenase, was employed. Similarly glycolytic potential based on the activity of alpha-glycerophosphate dehydrogenase was not affected by training. Glycogen concentration was elevated by 60% (P less than 0.01) in type I fibers and 77% (P less than 0.01) in type IIb fibers with training but was not altered (P greater than 0.05) in type IIa fibers. Reductions (P less than 0.05) in fiber area ranging from 11 to 20% were observed in all fiber types as a result of training, whereas the number of capillaries per fiber remained static.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

A comparative histochemical and morphometric study of canine skeletal muscle.

The purpose of this study was to determine whether there were differences in skeletal muscle properties in the hindlimb muscles of different types of dogs. Muscle samples were obtained from the gracilis, sartorius cranial head, sartorius caudal head and tibialis anterior muscles of mixed-breed and hound-type dogs and Beagles. Fiber type, fiber size and capillary morphometry determinations of each muscle from each dog were made from sections stained for myofibrillar ATPase activity. Individual animals were bilaterally symmetric for all measured variables. Fiber type, fiber size and capillary geometry varied between dogs of a given type and muscles within a given dog. There were no differences between dog types for fiber type or fiber size; significant variation in log(muscle)/log(body) mass ratios between dog types was observed for all muscles. The results indicate that for a given muscle, significant variation can occur in skeletal muscle characteristics between different types of dogs and that these differences can be independent of differences in exercise history.

Adenosine Triphosphatases↗
PubMed1988

Myosin light chains in regenerating rat skeletal muscle following chronic, low-frequency, electrical stimulation.

Ten days of chronic, low-frequency, electrical stimulation of regenerating rat extensor digitorum longus muscle causes an increase in the percentage of slow, phosphorylatable myosin light chains with a complementary decrease in the total fast light chain content. This altered light chain expression is similar to that observed when electrical stimulation is applied to a developing muscle in vivo.

Animals↗
PubMed1988

Residual volume as a tool in body fat prediction.

Possible methods of estimating residual volume for the prediction of body fat have been compared in young and healthy adults, with particular reference to the potential of a rapid helium equilibration method. In the first experiment, 5 women and 5 men performed nitrogen elimination, oxygen dilution and helium equilibration tests; scores for the helium test were higher than for the other two methods, but lay between the predictions made by Bass in 1964 and by Wilmore in 1969 and the values predicted by the equation of Goldman and Becklake in 1959. However, estimates of body density and body fat, based on residual volumes obtained from the prediction equations, did not differ significantly from those obtained directly by helium equilibration. A second experiment compared the helium and the oxygen techniques in 18 men and 18 women, with similar results. A final experiment compared the simple helium equilibration procedure with vital capacity and anthropometric predictions also suited to large scale determinations of body composition. It is concluded that the rapid helium equilibration procedure provides a fast and convenient procedure for the residual volume component of a body fat estimation. However, further study of the adequacy of equilibration is needed in older subjects and in patients with chronic chest disease.

Adipose Tissue↗
PubMed1988

Fiber type, fiber size, and capillary geometric features of the semitendinosus muscle in three types of dogs.

The fiber type, fiber size, and capillary geometric features were determined from the center of the proximal half of the left and right semitendinosus muscles in 5 mixed-breed dogs, 5 hound-type dogs, and 5 Beagles. There were no significant differences between the left and right muscles of each dog. Comparisons among the 3 groups of dogs revealed that the hound-type dogs had the largest fibers (type I and type II); however, the 3 groups were similar in their fiber-type percentages and their capillary geometric features.

Animals↗
PubMed1987

Effects of downhill or uphill training prior to a downhill run.

Nine men volunteered to undergo 10% downhill (DT) or 10% uphill (UT) treadmill training at 60% VO2max for 12 minutes on two consecutive days. Four days later the downhill run (DR) was repeated. All subjects reported considerable muscular soreness following DT but not UT. When DR followed UT muscular soreness was again reported but not when DR followed DT. Peak knee flexion and extension moment of force data at five angular velocities, ranging from 0.52-4.71 rad s-1, were reduced following DR regardless of whether soreness was present. During each run VO2 was stable during UT but drifted upwards during DT and DR. This increase in VO2 was not due to changes in the stride frequency since the stride frequency remained nearly constant on all days except for the second day of the DT when an increase of 20 strides per minute occurred; this was the only day the subjects ran while sore. It was concluded that two 12 minute bouts of downhill running were sufficient to protect against the occurrence of muscular soreness in subsequent downhill run. However, this training was insufficient to prevent a 2-3 day loss of muscular strength. These results support the hypothesis that the sensation of delayed onset muscle soreness and the temporary strength loss associated with eccentric contraction have different physiological causes.

Adult↗
PubMed1987

Sleep deprivation and cardiorespiratory function. Influence of intermittent submaximal exercise.

The effects of 64 h of sleep deprivation upon cardiorespiratory function was studied in 11 young men (VO2max = 55.5 ml kg-1 min-1, STPD). Six subjects engaged in normal sedentary activities, while the others walked on a treadmill at 28% VO2max for one hour in every three; eight weeks later, sleep deprivation was repeated with a crossover of subjects. Immediate post-deprivation measurement of VO2max showed a small but statistically significant decrease (-3.8 ml min-1 kg-1, STPD), with no difference between exercise and control trials. The final decrement in aerobic power was not due to a loss of motivation, as 88% (21 of 24) of post-deprivation tests still showed a plateau of VO2max; in addition, terminal heart rates (198 vs 195 beats min-1), respiratory exchange ratios (1.14 vs 1.15) and blood lactate levels (12.1 vs 11.8 mmol l-1) were not significantly different after sleep deprivation. The decrease in VO2max was associated with a lower VEmax (127 vs 142 l min-1, BTPS) and a substantial haemodilution (13%). Physiological responses to sub-maximal exercise showed persistence of the normal diurnal rhythm in heart rate and oxygen consumption, with no added effects due to sleep deprivation. However, ratings of perceived exertion (Borg scale) increased significantly throughout sleep deprivation. The findings are consistent with a mild respiratory acidosis, secondary to reduced cortical arousal and/or a progressive depletion of tissue glycogen stores which are not altered appreciably by moderate physical activity.

Adult↗
PubMed1987

Specific muscular development in under-18 soccer players.

A comparison of the under-18 (U-18) and under-16 (U-16) squads of the Canadian national soccer team with a representative sample of Canadians (Canada Fitness Survey, 1983) showed a tendency for the development or selection of the older players in teams of stature (U-18, 175.8 cm; U-16, 171.1 cm; CFS, 170.9 cm) and lean body mass (U-18, 63.4; U-16, 57.9; CFS, 54.2 kg). The larger lean mass of the older players could not be explained simply by size. The U-18s also showed greater isokinetic leg extension force (particularly for rapid movements) and explosive strength (vertical jump) relative to the younger players, although the knee extension force was less than in some classes of athlete. Part of the gain in mass seems due to local training of the hip and leg muscles and part to a more general muscular development. Contrary to some reports, the hip flexibility of the Canadian players (sit and reach test) was greater than for a national sample; this may be important in avoiding soft tissue injuries to the legs. However, aerobic power (58.3 +/- 5.3 ml kg-1 min-1) and body fat (8.0 +/- 1.1%) were unremarkable.

Adolescent↗