Alterations in blood volume following short-term supramaximal exercise

To investigate the role of high-intensity intermittent exercise on adaptations in blood volume and selected hematological measures, four male subjects aged 19-23 yr [peak O2 consumption (VO2max) = 53 ml X min-1 X kg-1] performed supramaximal (120% VO2max) cycle exercise on 3 consecutive days. Each exercise session consisted of intermittent work performed as bouts of 1-min work to 4-min rest until fatigue or until a maximum of 24 repetitions had been completed. Measurements on blood samples were made before the exercise period and 24 h after the last exercise session. Plasma volume (PV) estimated using 131I-human serum albumin increased by 11.6% (3,504 vs. 3,912 ml; P less than 0.05). Total blood volume (TBV) based on PV and hematocrit (Hct) values increased by 4.5% (5,798 vs. 6,059 ml; P less than 0.05), whereas red cell volume (RCV) decreased by 6.4% (2,294 vs. 2,147 ml; P less than 0.05). Measurements of hematological indices indicated significant reductions (P less than 0.05) in whole-blood Hct (39.7 vs. 35.5%), hemoglobin concentration (15.5 vs. 13.9 g/100 ml), hemoglobin content (897 vs. 839 g), and red blood cell count (5.15 vs. 4.55 X 10(6) X mm-3). The findings of this study suggest that exercise intensity is a major factor in promoting exercise-induced hypervolemia and that rapid elevations in PV can be induced early in training.

Inter- and intraspecies comparisons of fibre type distribution and of succinate dehydrogenase activity in type I, IIA and IIB fibres of mammalian diaphragms

Fibre types in the costal region of the diaphragm muscle of several mammalian species with widely different respiratory rates were examined microphotometrically for succinate dehydrogenase (SDH) activity. Mean activities indicated no significant (p greater than 0.05) difference between the type I and IIA fibres for any of the species examined. SDH activities in type IIB fibres were significantly lower (p less than 0.05) than either the type I or type IIA fibres in the cat, guinea pig, rat and rabbit whereas in the mouse no difference was found. The dog had no classical type 1B fibres. Analysis of the distribution of SDH activities by fibre type indicated a wide scattering of scores with no distinct separation between fibre types. Large differences in SDH activity were noted between species. Mean SDH activities were highest in the mouse and rat, intermediate in the rabbit and guinea pig and lowest in the cat and dog. These data suggest an association between respiratory rate and aerobic oxidative potential of the various fibre types in diaphragms of the species examined.

Fibre type specific transformations in the enzyme activity pattern of rat vastus lateralis muscle by prolonged endurance training

The alterations in activity patterns of representative enzymes in energy metabolism were investigated in the superficial (white) and deep (red) portions of the fast vastus lateralis muscle of the adult rat in response to prolonged endurance training. It was found that following 15 weeks of extreme training (final running duration: 210 min per day, 27 m/min at 15 degree grade), increases in the activities of marker enzymes of the citric acid cycle (citrate synthase), beta-oxidation (3-hydroxyacyl CoA dehydrogenase), and ketone body utilization (3-ketoacid CoA transferase) as well as of glutamate pyruvate transaminase occurred in both regions of the muscle, with the greatest increase being observed in the superficial portion (2.6-4.2-fold). Pronounced increases were also seen for hexokinase which showed highest activities after 7 weeks of training. Conversely, decreases were noted for various glycogenolytic, glycolytic and gluconeogenic enzymes (phosphorylase, glyceraldehydephosphate dehydrogenase, pyruvate kinase, lactate dehydrogenase and fructose-1,6-diphosphatase). Reduction in the activities of these enzymes was most pronounced in the deep portion of the muscle. These results demonstrate a fundamental rearrangement of the energy metabolism of the muscle in response to prolonged, high intensity training. In the case of the deep portion of the vastus lateralis muscle, which has been shown to be composed of a large percentage of fast oxidative-glycolytic fibres (FOG), the enzyme profile becomes similar to the slow oxidative (SO) fibre. In the superficial portion which contains predominantly fast glycolytic fibres (FG), the enzyme profile becomes similar to FOG fibres.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of oral propranolol and exercise protocol on indices of aerobic function in normal man

The exercise responses to two different progressive, upright cycle ergometer tests were studied in nine healthy, young subjects either with no drug (ND) or following 48 h or oral propranolol (P) (40 mg q.i.d.). The ergometer tests increased work rate by 30 W either every 30 s or every 4 min. Propranolol caused a significant (p less than 0.05) reduction in peak oxygen uptake (VO2) during both the 30-s and 4-min tests (30-s ND, 3949 +/- 718 mL X min-1 (means +/- SD); 30-s P, 3408 +/- 778 mL X min-1; 4-min ND, 4058 +/- 409 mL X min-1; 4-min P, 3725 +/- 573 mL X min-1). There was no difference between 30-s ND and 4-min ND for peak VO2. The ventilatory anaerobic threshold was not significantly different between any test (30-s ND, 2337 +/- 434 mL O2 X min-1; 30-s P, 2174 +/- 406 mL O2 X min-1; ND, 2433 +/- 685 mL O2 X min-1; 4-min P, 2296 +/- 604 mL O2 X min-1). The VO2 at which blood lactate had increased by 0.5 mM above resting levels was significantly lower than the ventilatory anaerobic threshold for the 4-min ND (1917 +/- 489) and the 4-min P (1978 +/- 412) tests, but was not different for the 30-s ND and 30-s P tests. At exhaustion in the progressive tests, the blood PCO2 was higher (p less than 0.05) in both 30-s tests than 4-min tests.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaerobic threshold, blood lactate, and muscle metabolites in progressive exercise

The purpose of this study was to investigate the interrelationship between the ventilatory anaerobic threshold (VAT), the blood lactate anaerobic threshold (LAT), and the alteration in muscle metabolism. Ten subjects (5 men and 5 women) performed progressive exercise to exhaustion on two occasions for determination of the VAT and the LAT. For both AT criteria, the initial breakpoints (P less than 0.05) in the relationship between ventilation (VE) and O2 uptake (VO2VAT) and lactate (La) and power output (POLAT) were determined by multisegmental linear regression. During three subsequent tests the subjects performed progressive exercise to various percentages of the VO2VAT. Biopsies were obtained from the musculus vastus lateralis for determination of selected glycolytic intermediates at the cessation of exercise. It was found that the VO2VAT, expressed in terms of power output (POVAT), occurred at a higher value (P less than 0.05) than the POLAT (1,004 vs. 621 kg X min-1). Blood La values at these power outputs were 2.09 and 1.25 mM, respectively. Determination of the muscle La concentration at 79, 94, and 110% of VO2VAT indicated significant increases (P less than 0.05) from rest values of 1.59 to 4.49, 6.37, and 11.3 mmol X kg wet wt-1, respectively. It is concluded that the gas exchange AT as determined by the relationship between VE and VO2VAT and the AT as determined by blood La accumulation (LAT) are not coincidental. In addition the elevation in muscle anaerobic glycolysis precedes both the VAT and the blood LAT in this progressive exercise test.

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.

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.

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.

A computer linear regression model to determine ventilatory anaerobic threshold

The anaerobic threshold has generally been determined by simple visual inspection of ventilation or other gas-exchange data obtained during incremental exercise. To establish objective criteria for the determination of anaerobic threshold, a computer algorithm has been developed that models the ventilatory response to exercise using multisegment linear regression. The best-fit regression model is chosen by minimizing the pooled residual sum of squares . The anaerobic threshold is reported as the first break point in that model. The computer-determined anaerobic threshold values for 37 subjects were compared with subjectively determined values as chosen by four independent observers. The observers' estimates, when pooled to yield a single a single value for each subject, gave a mean value for the gas-exchange anaerobic threshold of 2.26 +/- 0.69 l/min. The estimates by the computer method averaged 2.21 +/- 0.65 l/min. The correlation coefficient for these two methods was 0.94.

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.

Blood acid-base and lactate relationships studied by ramp work tests

The effect of work rate increase in ramp work tests was studied in six healthy subjects. Each subject exercised on a cycle ergometer with the work rate incremented by either 65.4 W . min-1 and 49.0 W . min-1 for the fast ramps or 8.2 W . min-1 and 6.1 W . min-1 for the slow ramps for male and female subjects, respectively. Gas exchange was monitored by open-circuit spirometry. Arterialized venous blood samples were obtained from a dorsal hand vein. The peak VO2 was not significantly different for fast (3218 +/- 602 ml . min-1, X +/- SD) and slow (3237 +/- 601 ml . min-1) ramp tests. Gas-exchange anaerobic threshold, determined by multi-segment linear regression of VE vs VO2, was similar for fast and slow ramp tests (1742 +/- 415 and 1925 +/- 639 ml O2 . min-1, P greater than 0.05). The VO2 at which blood lactate increased 0.5 mM above resting levels was lower (1463 +/- 259 ml . min-1, P less than 0.05) than the gas-exchange anaerobic threshold for the slow ramp test. The VO2 at which blood lactate reached 2.0 mM was greater (2383 +/- 247 ml . min-1, P less than 0.05) than the gas-exchange anaerobic threshold for the fast ramp test. In addition to these lactate differences, blood pH and HCO3- did not change in direct proportion to the lactate concentration in either test. Blood PCO2 was significantly (P less than 0.05) greater at the point of exhaustion in the fast ramp test (42.2 +/- 2.3 mmHg) than in the slow ramp test (26.7 +/- 2.1 mmHg). It is concluded that the gas-exchange anaerobic threshold can be clearly dissociated from the blood lactate threshold by altering the work rate forcing function. Other mechanisms, such as H+ efflux and CO2 storage capacity, are more likely explanations for the gas-exchange anaerobic threshold.

A comparison of two ATPase based schemes for histochemical muscle fibre typing in various mammals

A comparative study was performed on the fibre populations in tibialis anterior muscles of mouse, rat, guinea pig, rabbit, cat and dog using the two different methods of histochemical staining for myofibrillar ATPase after acid (Brooke and Kaiser 1970) or alkaline preincubations (Guth and Samaha 1970). For all species a complete correspondence existed between type I (Brooke and Kaiser 1970) and beta fibres (Samaha et al. 1970). Gross correspondence (greater than 85%) existed between IIA and IIB (Brooke and Kaiser 1970) and alpha beta and alpha fibres (Samaha et al. 1970) respectively in mouse, guinea pig, rabbit, cat and dog. In the case of mouse and dog, this high degree of correspondence was based on the assumption that mouse tibialis anterior contains no type I and the dog no type IIB fibres. For the rat, a pronounced overlap existed between IIA fibres on the one hand and alpha beta and alpha fibres on the other hand as well as between IIB fibres and alpha beta and alpha fibres. These observations lead to the conclusion that the two classification schemes are not interchangeable for all species and that the two terminologies should be used only in relation with the methods from which they were derived.

Human vastus lateralis and gastrocnemius muscles. A comparative histochemical and biochemical analysis

Two muscles involved in locomotion the vastus lateralis and the gastrocnemius, were compared on a variety of histochemical an biochemical properties. Ten active males, age 20 - 24 years, served as subjects. Fibre type distributions, type I, type IIA and type IIB, as determined from samples extracted by muscle biopsy were similar in both muscles. In addition, no significant difference (p greater than 0.05) was found between fibre types in each muscle for fibre size, relative area, capillaries per fibre and the ratio of capillaries per fibre area. The activities of a number of enzymes representative of energy supplying pathways - the citric acid cycle (succinate dehydrogenase, SHD; beta-hydroxyacyl CoA dehydrogenase, HADH), glycogenolysis (total phosphorylase, PHOSP), glycolysis (phosphofructokinase, PFK) - were of similar magnitude between the two muscles. The only exception noted was for the activity of a glycolytic enzyme, lactate dehydrogenase, LDH, where a 16% higher value was observed in the vastus lateralis. The close degree of homogeneity displayed between these two muscles may be of significance in providing for a functional synchrony to occur in locomotor activities of varying intensity.

The Effect of Rapid Weight Loss on Physiological Functions in Wrestlers

In brief: To assess the effects of rapid weight reduction, four university wrestlers decreased their body weight by 8% over a four-day period by food and liquid intake reductions. Significant decreases in muscle glycogen concentration and dynamic strength, but not aerobic or anaerobic capacity, accompanied weight loss. A three-hour rehydration period did not improve glycogen levels or strength performance. These results suggest that rapid weight reduction may impair wrestling performance.

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.

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.

Biochemical and histochemical alterations in skeletal muscle in man during a period of reduced activity

This study investigated the hypothesis that the adaptations in skeletal muscle to prolonged exercise overload, involving high levels of adenosine triphosphate (ATP) resynthesis, result in a preferential adaptation to pathways involved in energy metabolism. The change in selected properties of skeletal muscle during a period of reduced activity was used as an indication of training-induced adaptations. Muscle biopsy samples from the vastus lateralis were analyzed 6 weeks and 18 weeks after a 5-month, intense, intermittent training program. Significant reductions occurred (p less than 0.05) in enzyme activities representative of the citric acid cycle (succinic dehydrogenase, SDH), beta oxidation of free fatty acids (3-hydroxyacyl CoA dehydrogenase, HADH), glycogenolysis (total phosphorylase, PHOSP), and glycolysis (phosphofructokinase, PFK). In addition, reductions in concentration (p less than 0.05) were also found for ATP, creatine phosphate (CP), and glycogen. With the exception of PFK, all enzyme changes and the high energy phosphates reached new stable levels by at least the 6th week of detraining. The absence of changes in muscle cell type and size during the detraining period supports the hypothesis that adaptations in energy potential of the muscle cell predominate in this type of high intensity overload situation.

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.

Open-circuit gas exchange analysis in the non-steady-state

The serial measurement of oxygen uptake (VO2) of four subjects was calculated during the transition from rest to constant-load cycle ergometer work using an open-circuit gas exchange analysis system. In calculating VO2, the mixed expired gas concentrations were matched with the ventilatory volume by various delay factors. A delay factor equivalent to the passing of 20 L of expired ventilation through the mixing chamber yielded results which were most similar to the VO2 obtained by a computerized breath-by-breath analysis. Previous checks of the response of the system to changes in calibrating gas mixtures had indicated that it was necessary to pass approximately 20-25 L of gas through the system before a plateau response was observed. This volume remained relatively constant, independent of flow rate. It is proposed that an understanding of the response characteristics of an open circuit system will enable the accurate calculation of VO2 over short time intervals in the non-steady-state.