Time-dependent effects of short-term training on muscle metabolism during the early phase of exercise.

In this study, we investigated the hypothesis that the metabolic adaptations observed during steady-state exercise soon after the onset of training would be displayed during the nonsteady period of moderate exercise and would occur in the absence of increases in peak aerobic power (Vo2peak) and in muscle oxidative potential. Nine untrained males [age = 20.8 +/- 0.70 (SE) yr] performed a cycle task at 62% Vo2peak before (Pre-T) and after (Post-T) training for 2 h/day for 5 days at task intensity. Tissue samples extracted from the vastus lateralis at 0 min (before exercise) and at 10, 60, and 180 s of exercise, indicated that at Pre-T, reductions (P < 0.05) in phosphocreatine and increases (P < 0.05) in creatine, inorganic phosphate, calculated free ADP, and free AMP occurred at 60 and 180 s but not at 10 s. At Post-T, the concentrations of all metabolites were blunted (P < 0.05) at 60 s. Training also reduced (P < 0.05) the increase in lactate and the lactate-to-pyruvate ratio observed during exercise at Pre-T. These adaptations occurred in the absence of change in Vo2peak (47.8 +/- 1.7 vs. 49.2 +/- 1.7 mlxkg(-1)xmin(-1)) and in the activities (molxkg protein(-1)xh(-1)) of succinic dehydrogenase (3.48 +/- 0.21 vs. 3.77 +/- 0.35) and citrate synthase (7.48 +/- 0.61 vs. 8.52 +/- 0.65) but not cytochrome oxidase (70.8 +/- 5.1 vs. 79.6 +/- 6.6 U/g protein; P < 0.05). It is concluded that the tighter metabolic control observed following short-term training is initially expressed during the nonsteady state, probably as a result of increases in oxidative phosphorylation that is not dependent on changes in Vo2peak while the role of oxidative potential remains uncertain.

Failure of hypoxia to exaggerate the metabolic stress in working muscle following short-term training.

This study investigated the effects of hypoxia (experiment 1) and the effects of hypoxia following short-term training (experiment 2) on metabolism in working muscle. In experiment 1, eight males with a peak aerobic power (VO2peak) of 45 +/- 1.7 ml x kg(-1) x min(-1) (x +/- SE) cycled for 15 min at 66.1 +/- 2.1% VO2peak while breathing room air [normoxia (N)] or 14% O(2) [hypoxia (H)]. In experiment 2, nine males with a VO2peak of 43.3 +/- 1.6 ml x kg(-1) x min(-1) performed a similar protocol at 60.7 +/- 1.4% VO2peak during N and during H following 5 days of submaximal exercise training (H + T). Tissue samples extracted from the vastus lateralis before exercise and at 1, 3, and 15 min of exercise indicated that compared with N, H resulted in lower (P < 0.05) concentrations (mmol/kg dry wt) of creatine phosphate and higher (P < 0.05) concentrations of creatine, inorganic phosphate, and lactate, regardless of exercise time. When the exercise was performed at H + T and compared with N, no differences were observed in creatine phosphate, creatine, inorganic phosphate, and lactate, regardless of duration. Given the well-documented effects of the short-term training model on elevating VO2 kinetics and attenuating the alterations in high-energy phosphate metabolism and lactate accumulation, it would appear that the mechanism underlying the reversal of these adaptations during H is linked to a more rapid increase in oxidative phosphorylation, mediated by increased oxygen delivery and/or mitochondrial activation.

The effects of tendon load and posture on carpal tunnel pressure.

Two pressure measurement techniques (catheter and bulb) were used to decompose the effects of tendon loads on carpal tunnel pressure (CTP). The catheter technique measures true hydrostatic pressure, whereas the bulb technique is a estimate of contact force or pressure on the median nerve. Eight cadaveric wrists were moved through a range of flexion-extension (0 degrees, 10 degrees, 20 degrees, 30 degrees, and 45 degrees of each) and radioulnar deviation (10 degrees and 20 degrees radial and 0 degrees, 10 degrees, 20 degrees, and 30 degrees ulnar) while CTPs were measured under 4 muscle loading conditions with the thumb, index, and long finger in a pinch-grip posture. The first of these was zero load. Then a 1-kg mass was applied in turn to both flexors of the index and long fingers, the palmaris longus (PL); and the flexor pollicis longus. The hydrostatic pressure was found to be affected by both wrist posture and tendon load. With no load, highest pressures were seen in wrist extension. Muscular loading elevated CPT, particularly the loading of palmaris longus with the wrist in extension and the digital flexors with the wrist flexed. Bulb pressure measurements, related to local contact forces by the digital flexors, indicated the highest loads on the median nerve with the wrist flexed. Palmaris longus loading created the highest pressures in extension and only moderate pressure in flexion, indicating that it may alter the geometry of the transverse carpal ligament. In view of the data from this study, it is necessary to incorporate measures of hydrostatic pressure and local contact forces to describe possible trauma to the median nerve in the carpal tunnel, as neither appears sufficient when used independently.

Passive properties of the forearm musculature with reference to hand and finger postures.

OBJECTIVE: To quantify individual forearm muscle passive forces and evaluate their impact on hand function. DESIGN: The passive force-length properties of the 24 extrinsic hand and wrist muscles were determined in five fresh frozen cadaver arms. BACKGROUND: Muscle force production is a summation of the active and passive force components. The passive properties of the extrinsic finger musculature and wrist musculature appear to strongly affect both hand posture and hand movement. METHODS: The passive force-length properties of extrinsic hand and wrist muscles were determined by applying a slow, continuous extension to each muscle and recording the resulting tension. Each force-length curve was fit using exponential regression and were related to specific joint rotations and seven hand postures by calculating the muscle excursions for those postures. RESULTS: The exponential passive force-length relationship explained over 97% of the experimental variance. The largest passive forces were elicited in the digital extensors in grips involving large flexion angles such as tip pinch, key pinch, and a briefcase grip. CONCLUSIONS: The passive properties of the extrinsic finger musculature and wrist musculature affect both hand posture and movement especially in postures with flexed wrist and fingers.

Lumbrical function: interaction of lumbrical contraction with the elasticity of the extrinsic finger muscles and its effect on metacarpophalangeal equilibrium.

Since conflicting statements have been made in the literature regarding the influence of lumbrical contraction on the metacarpophalangeal (MP) joint, a study was undertaken to determine the length-tension curve for the index flexor profundus. Four fresh cadaver hands were used. Measurements for the flexor superficialis and for the common extensor were determined in there. The measurements were correlated with measured displacement of these tendons in six finger positions. Isolated lumbrical contraction was then mechanically simulated, acting against spring homologues of the index extrinsic muscles. The finger moved from the rest position toward the intrinsic position with loads of less than 5 N. This demonstrated that in addition to its effect on interphalangeal joint extension, the lumbrical acting alone can cause flexion of the metacarpophalangeal joint.

Lumbrical length changes in finger movement: a new method of study in fresh cadaver hands.

A new method of loading the lumbrical muscle in the cadaver hand, based on the bicycle brake cable concept, has been developed. The device can be inserted with the aid of tendon-tunneling forceps and sutured to the profundus tendon at the origin of the lumbrical muscle. Lumbrical function is stimulated by applying a force that approximates the attachment point on the profundus tendon to the lateral wing of the extensor expansion without predetermining which will move the origin, the insertion, or both. This preliminary study reports the use of this device in determining lumbrical length changes in five fresh cadaver hands as the index finger was passively moved through each of six standard finger positions. In the absence of other restraints lumbrical contraction causes the index finger to move from the claw position through the straight to the intrinsic position. The latter position represents maximum shortening.

Male and female differences in enzyme activities of energy metabolism in vastus lateralis muscle.

To investigate sex differences in the organization of enzyme activities of energy supplying metabolism in skeletal muscle, samples of the vastus lateralis were extracted from active but untrained males (n = 16) and females (n = 17), ranging in age from 18 to 22 years. Muscle tissue from 2 different biopsy samples from each subject were analyzed for enzymes representative of the citric acid cycle (succinic dehydrogenase, SDH), beta-oxidation of fatty acids (3-hydroxyacyl CoA dehydrogenase, HAD), glycogenolysis (phosphorylase, PHOSPH), glycolysis (pyruvate kinase, PK; phosphofructokinase, PFK and lactate dehydrogenase, LDH) and glucose phosphorylation (hexokinase, HK). The results indicated that the maximal activities of PFK, PK, LDH and PHOSPH, HK and SDH averaged between 15 and 32% higher in the males than in the females. No significant differences between the sexes were found for HAD. When enzyme activity ratios were calculated, sex differences were only evident for the HAD/SDH ratio (mean +/- SD; females = 0.56 +/- 0.20; males = 0.41 +/- 0.11 and for the PFK/HAD ratio (females = 7.40 +/- 1.6; males = 9.58 +/- 1.9). The findings suggest that (1) the females have a significantly lower overall capacity for aerobic oxidation and for anaerobic glycolysis than the males; (2) the females have a greater capacity for beta-oxidation relative to the capacity of the citric acid cycle; and (3) the glycolytic potential relative to the potential for beta-oxidation is lower in the females.

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.

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.

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.

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.

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.

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.

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.

The protective value of a neurovascular island pedicle transfer in hands partially anesthetic due to ulnar denervation in leprosy.

Neurovascular skin island transfers were performed with the prime objective of protecting vulnerable anesthetic areas on the hands of patients with leprosy. After an average follow-up of eight years on sixteen patients, all had long-lasting protective benefits without further loss of tissue consequent to injury. At follow-up, two-point discrimination was less than ten millimeters in only one patient, more than twenty millimeters in ten, and indeterminate in five. Sensory misreference persisted in fourteen patients. Axon sprouting was evident in six but only over short distances (four to eight millimeters beyond the island). Compared with the intact side of the donor finger, nine of the sixteen transfers had lost some sensitivity but sensation was rated normal in one, nearly normal in six, and protective only in nine. The loss of sensation in the donor finger was less than expected and was not a problem. Scar contracture occurred in two donor and five recipient fingers, but this could be attributed to placement of the incision too far anteriorly, and hence was an unavoidable complication. Restoration of protective sensation to the ulnar border of the hand, whatever the cause of anesthesia, is considered extremely worth while.