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Biomedical subjects

M E Houston

Publications and source records attributed to M E Houston.

At least 73 records · Page 4Linked to original sources
PubMed1983

Alterations in human muscle fibre type distribution induced by acute exercise.

Fibre type distributions in the vastus lateralis muscles of six male subjects (age 18 to 22 years) have been compared at rest and during exercise. Exercise consisted of one leg cycling at 60% VO2 max (one leg) for 120 min. The increased contractile activity was associated with a 28.8% (p less than 0.05) decrease in the distribution of Type I fibres in the exercised leg. This change in fibre type distribution was manifested early in the exercise (15 min), and was also evident in muscle samples obtained after 60 and 120 min of activity. Reductions in the Type I fibre distribution was accompanied by an increase in the Type II fibres, specifically the Type IIA distribution (p less than 0.05). Comparable alterations in the specific fibre distribution were also found in the non exercising leg. These observations indicate that alterations in the muscle cell induced either directly or indirectly by the increased contractile activity interact with normal pre-incubation conditions to effect changes in the stability of the myofibrillar ATPase reaction. Specifically, it appears that a percentage of the Type I fibre population becomes acid labile and alkali stable.

Adenosine Triphosphatases↗
PubMed1983

Muscle performance, morphology and metabolic capacity during strength training and detraining: a one leg model.

To investigate biochemical, histochemical and contractile properties associated with strength training and detraining, six adult males were studied during and after 10 weeks of dynamic strength training for the quadriceps muscle group of one leg, as well as during and after a subsequent 12 weeks of detraining. Peak torque outputs at the velocities tested (0-270 degrees X s-1) were increased (p less than 0.05) by 39-60% and 12-37% after training for the trained and untrained legs, respectively. No significant changes in peak torques were observed in six control subjects tested at the same times. Significant decreases in strength performance of the trained leg (16-21%) and untrained leg (10-15%) were observed only after 12 weeks of detraining. Training resulted in an increase (p less than 0.05) in the area of FTa (21%) and FTb (18%) fibres, while detraining was associated with a 12% decrease in FTb fibre cross-sectional area. However, fibre area changes were only noted in the trained leg. Neither training nor detaining had any significant effect on the specific activity of magnesium-activated myofibrillar ATPase or on the activities of enzymes of phosphagen, glycolytic or oxidative metabolism in serial muscle biopsy samples from both legs. In the absence of any changes in muscle enzyme activities and with only modest changes in FT fibre areas in the trained leg, the significant alterations in peak torque outputs with both legs suggest that neural adaptations play a prominent role in strength performance with training and detraining.

Adaptation, Physiological↗
PubMed1983

Specificity of physiologic adaptations resulting from ice-hockey training.

The specificity of the metabolic and cardiorespiratory responses to varied seasonal training programs and to varied testing modalities and protocols were investigated in two groups of college hockey players. Training consisted of either ice hockey (IH) or a combination of ice hockey and prolonged low-intensity cycling (IH-C). Measurement of training-induced adaptations were determined during maximal and submaximal ice skating, and during maximal and submaximal cycling. Ice hockey training caused no change in VO2max, maximal heart rate (HRmax), and maximal ventilation (VEmax) during maximal ice skating. During submaximal ice skating following IH training, however, reductions (P less than 0.05) in blood lactate (La), VE/VO2, and respiratory exchange ratio (R) were observed. When maximal and submaximal cycling was employed as the test modality, no training-induced alteration was found. The IH-C training program (ice hockey-cycling) resulted in adaptations similar to those observed during submaximal ice skating following the IH training. In addition, a reduction (P less than 0.05) in heart rate was observed during submaximal cycling exercise. From these findings it appeared that the adaptive response to training may be specific to the type of work used in training, the type of ergometry used to evaluate training, and to specific physiological processes. In addition, these results suggested a dissociation between local and central adaptations.

Adult↗
PubMed1983

Glycogen depletion and lactate responses in freestyle wrestling.

Metabolic responses to international freestyle wrestling were investigated in six university wrestlers, four of whom were studied on two separate occasions. Lactate concentration in venous blood averaged 10.5 mM after the six minute bouts, while blood pH was (p less than 0.01) reduced to 7.063 +/- 0.061 (mean +/- S.D.) after wrestling. Glycogen concentration in biopsy samples from the vastus lateralis muscle was lower by 10.0 +/- 4.4 mmoles glucose units/kg wet muscle weight (p less than 0.01) after, compared to before wrestling. Evaluation of glycogen utilization in individual muscle fibre types using the periodic acid Schiff histochemical stain revealed that glycogen depletion, although modest, was similar in ST, FTa and FTb fibres. These data demonstrate that wrestling involves significant anaerobic metabolism, and that the vastus lateralis muscle is significantly involved in wrestling performance.

Adult↗
PubMed1982

Cross-adaptive responses to different forms of leg training: skeletal muscle biochemistry and histochemistry.

The influence of a program of high intensity training and of a combined program of high intensity training and prolonged submaximal training on adaptations to the vastus lateralis muscle was investigated in two groups of elite athletes. The high intensity training (H) consisted of ice hockey practices and games over a 14-week period while the combined program (HI-LO) included the addition of supplementary sessions of cycling, three times per week, progressively increasing from 30 to 45 min per session and at an intensity of 70% VO2max. Determinations of enzyme activities representative of energy supplying pathways revealed no change in 3-hydroxyacl CoA dehydrogenase (HADH), total phosphorylase (PHOSP), phosphofructokinase (PFK), lactate dehydrogenase (LDH), and a 7% increase (p less than 0.05) in succinate dehydrogenase (SDH). The addition of the supplementary program caused no further adaptation in the metabolic profile. Similarly, neither the HI nor the HI-LO program induced any alteration in the percentage fibre type (slow twitch (ST) vs. fast twitch (FT) or the subtypes (FTa, FTb, FTc). Reductions in the size (p less than 0.05) of ST fibres were noted for both the HI and the HI-LO training programs. In contrast, increases in capillarization (p less than 0.05) were found for both the ST (23%) and FTa (32%) fibres for the HI-LO program whereas a reduction in capillarization (21%) occurred in the FTa fibres as a result of HI training only. It is concluded that metabolic differentiation does not appear to occur in a manner consistent with the conditions of energy expenditure at least for high intensity work.

Adaptation, Physiological↗
PubMed1982

Metabolic effects of two frequencies of short-term surface electrical stimulation on human muscle.

The acute effects of two different frequencies of electrical stimulation on the metabolism of the vastus lateralis muscle were studied in young male and female adults. The quadriceps muscle group of one leg was stimulated for 60 min using surface electrodes that delivered square pulses of 0.6 ms duration, either continuously at 10 Hz (n = 5) or intermittently (n = 5) at 50 Hz (12 s stimulation, 48 s recovery). Biochemical analyses revealed no significant differences in glycogen or metabolite concentrations between the two conditions. Muscle lactate and citrate concentrations were increased (p less than 0.05) for both conditions, but ATP and CP concentrations were not significantly changed from rest values after stimulation. Glycogen concentrations decreased (p less than 0.05) by 24.6 and 29.1 mmol glucose units/kg after 60 min of 50 Hz and 10 Hz stimulation, respectively. Muscle fibres were identified as slow twitch (ST) and fast twitch a and b (FTa and FTb) on the basis of myofibrillar ATPase activity. Estimates of glycogen depletion in different fibre types using histochemical techniques revealed that FTa and FTb fibres had lower glycogen contents than ST fibres after 10 Hz stimulation whereas glycogen was moderately reduced in approximately 50% of all fibre types following 50 Hz stimulation. The modest changes observed in muscle metabolism following 60 min of stimulation were less than has been noted following traditional exercise, and suggest that only some of the muscle fibres were activated in the stimulated muscles at the depth where biopsy samples were removed.

Adult↗
PubMed1982

Leg muscle performance of athletes with and without knee support braces.

The effects of wearing and not wearing prescribed knee support braces on leg muscle performance were studied in 7 male athletes. Mean maximal torque outputs during isokinetic knee extension contractions with braces were significantly lower 12 to 30% compared to corresponding values without knee braces. Differences between the 2 conditions were more prominent during faster contractions. Maximal velocity measured during unloaded knee extension was 20% higher when subjects did not wear their braces. In addition, vertical velocity during a short all-out stair run was slower (p less than 0.01) with braces. At the conclusion of a 15-minute ride on a bicycle ergometer at a fixed load, lactate concentration was 41% higher in blood of subjects who wore knee braces. These data demonstrate that potential benefits of support braces for knee instability come at the expense of impaired performance.

Adult↗
PubMed1981

Physiological and muscle enzyme adaptations to two different intensities of swim training.

To test the hypothesis that a smaller quantity of high intensity (HI) as opposed to a larger quantity of moderate intensity (MI) swim training would result in adaptations more specific to the short performance times of swimming competitions, two groups of elite university swimmers were tested before and after 6.5 weeks of specific HI or MI intermittent swim training. In training, swimming times were faster and blood lactate concentrations were higher (10.2 vs. 7.5 mM) during HI compared to MI training. No significant differences were observed between the two groups for any of the variables measured, before or after training. However, significant increases with training were observed for the activities of hexokinase, phosphorylase, phosphofructokinase, succinate dehydrogenase, and 3-hydroxyacyl CoA dehydrogenase in the deltoid, but not the gastrocnemius muscles. Training resulted in significant increases in VO2 max during treadmill running, but not during tethered swimming. It is concluded that a larger quantity of MI swim training results in physiological adaptations that are similar to those obtained with a smaller quantity of HI training, at least over a relatively short training period.

Adult↗
PubMed1981

Skeletal muscle and physiologic characteristics of a world champion masters distance runner: a case study.

Physiologic and skeletal muscle characteristics of a world champion and world record holder Masters distance runner were evaluated in the context of his race performances at age 50 and 51. Comparisons were made to data on other middle-aged runners and on younger, elite distance runners. The subject had a VO2 max of 62.6 mL.kg-1.min-1, an average value for elite, middle-aged runners, but a low value compared to elite, younger distance runners. The subject had a smaller proportion of ST fibers in his gastrocnemius muscle (51.9%) compared to elite distance runners (mean 70.7%) However, the subject had a higher phosphorylase activity and a succinate dehydrogenase activity that was in the same range for younger, elite distance runners. In addition, the subject's gastrocnemius muscle was characterized by small ST and FT fibers with a large capillary density, favoring oxygen diffusion. Despite a relatively modest VO2 max value, the subject has demonstrated superior performance criteria in races from 3 to 42.2 km and an apparent ability to run for several hours at a high percentage of his VO2 max. These capabilities correspond to his large muscle metabolic capacity and enhanced muscle capillarization.

Age Factors↗
PubMed1980

Heat injuries in Canadian mass participation runs.

In two Canadian runs with a total of approximately 2900 participants 26 people collapsed with heat injury and were taken to hospital. All were relatively young (13 to 38 years old). A retrospective survey showed that all were novices to 10-km races and that many had collapsed even though they had consumed fluids before and during the run. A review of etiologic factors suggested that the extremes in the Canadian climate, which preclude heat acclimatization in the spring and early summer, may be an important influence on the incidence of heat injury.

Adolescent↗
PubMed1980

Diet, training and sleep: a survey study of elite Canadian swimmers.

A three day survey of food intake, training and sleep patterns was completed by 8 male and 12 female elite Canadian swimmers. Both groups were swimming similar training distances (ca. 9000m per day) and performed similar flexibility and strength training exercises. Males averaged 5 and females 4 meals per day (p < 0.05). In addition, the male swimmers are significantly more food from the meat, milk and grain food groups, taking in nearly twice as many calories as the female swimmers. The female swimmers were generally deficient in foods from the meat and milk group compared to recommended amounts. Twelve of the 20 athletes took additional food supplements. Both groups slept for similar periods of time each day (ca. 8h).

Calcium, Dietary↗
PubMed1979

Fiber composition, fiber size and enzyme activities in vastus lateralis of elite athletes involved in high intensity exercise.

In order to determine the influence of an extensive history of participation in high intensity activity on muscle fiber type, fiber size, and metabolic profile, elite ice hockey players were selected for investigation from three different leagues. Biopsy samples from the vastus lateralis muscle were obtained from different groups of players prior to and following the season and compared with control subjects. No significant differences were found in the percentage (49.6 vs. 43.8%) or the size of the ST fibers between the elite athletes and the control group, nor was there any significant alteration following the season of play in these variables. For the FT fiber subgroups, a reduction in the FTb (12.2 vs. 3.9%) and an increase in FTa (38.0 to 45.2%) fiber populations occurred over the season. Similarly, increases in fiber area were observed for both FT subgroups pre to post season. Of the enzymes studied only 3-hydroxyacyl CoA dehydrogenase was elevated in the post season measures, while total phosphorylase and phosphofructokinase were significantly lower. The metabolic pattern exhibited does not appear to be substantially different from what would be expected from an untrained group of similar fiber distribution.

Adolescent↗
PubMed1979

Muscle glycogen depletion patterns in fast twitch fibre subgroups of man during submaximal and supramaximal exercise.

Muscle glycogen depletion in ST, FTa and FTb fibres were studied in human subjects undergoing two distinctly different modes of bicycle exercise. Two hours of submaximal exercise (60% of VO2 max) produced a 77% decline in muscle glycogen concentration accompanied by only minor elevations in muscle and blood lactate levels whereas 10 one minute supramaximal work bouts resulted in a 52% decrease in total glycogen concentration and substantially elevated muscle and blood lactate contents. Moreover the patterns of glycogen depletion in the two conditions were also distinctly different. Based on the PAS staining intensity, glycogen was depleted the most in ST fibres and least in FTb fibres, during submaximal work. During supramaximal work FTb fibres were the lightest in PAS staining, with little loss of glycogen from ST fibres. In both situations the loss of glycogen in the FTa fibres was intermediate compared to the other two fibre types. These data support a selective recruitment of muscle fibres during work of different intensities, and further, suggest a physiological basis for the subgrouping of FT fibres in man.

Adult↗
PubMed1979

Interrelationships between skeletal muscle adaptations and performance as studied by detraining and retraining.

The effects of 15 days of detraining and 15 days of retraining were studied in 6 well-trained runners. Detraining resulted in significant decreases in the mean activities of succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) of 24% and 13% respectively, but no significant increases in these enzymes activities occured with retraining. Maximal oxygen uptake (VO2 max) decreased by 4% with detraining (p less than 0.05), and increased by a similar amount with retraining. Performance time in an intense submaximal run decreased by 25% (p less than 0.05) with inactivity, but still averaged 9% below the initial level after retraining. Maximal heart rate and peak heart rate during the performance run were higher after detraining by 4 and 9 beats per min, respectively (p less than 0.05). With retraining, these heart rate values were decreased by 7 and 9 beats per min (p less than 0.05). Blood lactate concentrations after the VO2 max and performance run were approximately 20% lower after detraining and retraining (p less than 0.05). Muscle fibre areas for three subjects tended to be larger in biopsy samples taken after detraining and retraining. These data suggest that even short periods of detraining result in significant changes in indices of physiological capacity and function in subjects near their upper limit of adaptation, and that a longer period of retraining is necessary for muscle to re-adapt to its original trained state.

Adaptation, Physiological↗
PubMed1979

The effect of water temperature on the hormonal response to prolonged swimming.

The relationship between thermoreception, hormonal secretion and muscular activity was studied. 6 men swam 60 min in 21, 27 and 33 degrees C water at a speed requiring 68% of VO2 max (determined in 27 degrees C water). Rectal temperature increased in 33 degrees C (1.3 +/- 0.2 degrees C, mean and S.E.) and 27 degrees C (0.7+/- 0.1 degrees C) expts. but decreased in 21 degrees C expts. (0.8 +/- 0.3 degrees C). Changes in esophageal and muscle temperatures parallelled changes in rectal temperature. Plasma noradrenaline was higher in 33 degrees C than in 27 degrees C expts. and growth hormone, cortisol and glucagon concentrations increased in 27 degrees C and 33 degrees C expts. only. Insulin concentrations were uniformly depressed during swimming at the different water temperatures. In 21 degrees C expts. noradrenaline and adrenaline concentrations were higher than in 27 degrees C expts. VO2, carbohydrate combustion and peak lactate were slightly lower in 33 degrees C expts. Plasma glucose decreased slightly and FFA and glycerol concentrations increased identically in all expts. Heart rate increased continuously during swimming in 27 degrees C and 33 degrees C expts., but not in 21 degrees C expts. In conclusion the rise in body temperatures normally observed during exercise enhances the exercise induced increases in the plasma concentrations of noradrenaline, cortisol, growth hormone and glucagon. Decreased body temperatures may elicit catecholamine secretion as a direct consequence of thermoreception. Shivering may account for previously observed decreases in insulin secretion during cold stress but not for increases in cortisol and growth hormone.

Adult↗
PubMed1979

Nutrition and ice hockey performance.

Muscle glycogen is a major fuel for ice hockey. About 60% of the muscle glycogen in quadriceps muscle is utilized during a single game. When hockey games are played on successive days, studies reveal that muscle glycogen utilized during the second game is less than that of the first game. The diet of seven professional hockey players was studied for one week during the playing season to determine whether food selection could pose a problem for hockey performance. The data reveal that most players have a high protein intake, but that vegetables and fruit intakes were low. The problem of fuel supply for young hockey players is examined during tournament situations where up to three or more games may be played in a single day.

Adult↗