Growth hormone deficiency and hyperthermia during exercise: a controlled study of sixteen GH-deficient patients.

Sweat secretion is often disturbed in patients with GH secretory disorders. Hyperhidrosis is a classic feature of acromegaly, and it has recently been shown that GH-deficient patients exhibit decreased sweating capacity after pilocarpine stimulation of the skin. Thus, patients with GH-deficiency may be at risk for developing hyperthermia. To pursue this, we performed a controlled study on sweating and body temperature regulation during exercise in the heat in 16 GH-treated GH-deficient patients with normalized insulin-like growth factor-I and insulin-like growth factor/binding protein-3 serum levels [11 with multiple pituitary deficiency (MPD) and 5 with isolated GH deficiency] and in 10 healthy subjects as controls (CTs). Each subject exercised on a bicycle ergometer for 60 min at a workload corresponding to 45% of their individual maximal oxygen consumption (VO2max), in a room maintained at 35 C. GH serum concentrations increased significantly after approximately 10 min of exercise in the CTs (P < 0.001) but remained low in the patients. Body heat storage was significantly higher in the patients compared with the CTs [89 (SE +/- 10) watts (MPD) vs. 37 (SE +/- 8) watts (CTs), P < 0.001]. Consequently, the core temperatures of the patients increased significantly after exercise compared with those of the CTs [38.3 C (0.10 C) (MPD) and 38.1 C (0.06 C) (isolated GH deficiency) vs. 37.5 C (0.2 C) (CTs) (P < 0.004)]. Skin temperature increased significantly during exercise in the patients but remained unaltered in the CTs. Sweat secretion rates, as determined by the pilocarpine method, were significantly lower in the MPD patients [77 (SE +/- 10) mg/30 min] than in the CTs [115 (SE +/- 7) mg/30 min] (P < 0.005). Total body sweating was lower in the patients than in the CTs, although the difference did not reach statistical significance. Significantly reduced estimated evaporative heat loss was demonstrated in the patients compared with the CTs (P < 0.001). In conclusion, 1) decreased sweating, decreased sensitivity of the sweat gland, and impaired thermoregulation are part of the adult GH-deficiency syndrome, and 2) GH-deficient patients are at risk for developing hyperthermia during physical activity in hot environments.

The effect of acute exercise on lymphocyte subsets, natural killer cells, proliferative responses, and cytokines in HIV-seropositive persons.

Eight healthy men infected with human immunodeficiency virus, type 1 (HIV) and eight HIV seronegative age- and sex-matched controls exercised on a bicycle ergometer (75% of VO2max, 1 h). The percentages of CD4+, CD4+45RA+, and CD4+45RO+ cells did not change, whereas the absolute number of CD4+ cells increased twofold during exercise and fell below prevalues 2 h after. The neutrophil count increase was more pronounced after exercise in the controls compared with in HIV-seropositive subjects. The percent CD16+ cells, and the natural killer (NK) and lymphokine activated killer (LAK) cell activity increased during exercise, but this increase was significantly less pronounced in the HIV-seropositive group. The results suggest that in response to physical stress, HIV-seropositive subjects have an impaired ability to mobilize neutrophils, NK and LAK cells to the blood. Furthermore, because the total number of CD4+ cells, but not the percentage of CD4+ cells, changed in response to exercise, this study further strengthens the idea that the percentage of CD4+ cells is preferable to the number of CD4+ cells in monitoring patients seropositive for HIV.

Bicycle exercise enhances plasma IL-6 but does not change IL-1 alpha, IL-1 beta, IL-6, or TNF-alpha pre-mRNA in BMNC.

The present study investigated the effect of concentric exercise on cytokine plasma levels and cytokine pre-mRNA in blood mononuclear cells (BMNCs). Healthy young moderately trained men performed ergometer bicycle exercise for 1 h at 75% of maximal oxygen uptake. The levels of plasma interleukin (IL)-6 increased significantly during exercise, but plasma levels of IL-1 alpha, IL-1 beta, and tumor necrosis factor-alpha (TNF-alpha) were below the detection limit in most subjects. Pre-mRNA for IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha could be detected in BMNCs, but the amounts did not change in relation to exercise. These results indicate that, although the absolute number of monocytes increases during exercise and the percentage of CD14+/HLA-DR+ and CD14+/HLA-DR- monocytes increases after exercise, the increased plasma levels of IL-6 during exercise is not likely to be a result of activated monocytes in peripheral blood.

Glutamine supplementation further enhances exercise-induced plasma IL-6.

Exercise stimulates the production and release of interleukin-6 (IL-6) from skeletal muscle. Glutamine is also synthesized in skeletal muscle and is involved in protein synthesis within this tissue. During exercise, plasma levels of glutamine decline, and this may affect the concentration of plasma IL-6 via a decrease in IL-6 synthesis and release from muscle. We hypothesized that glutamine supplementation would attenuate the exercise-induced decrease in plasma glutamine concentration and, thus, further enhance levels of plasma IL-6. Eight healthy men participated in a randomized, double-blind, crossover study in which they performed 2 h of cycle ergometry at 75% of peak O2 uptake. They received glutamine, glutamine-rich protein, or placebo supplementation at intervals during and 2 h after exercise. Exercise induced an 11-fold increase in plasma IL-6, which was further enhanced by glutamine (18-fold) and glutamine-rich protein (14-fold) supplementation, administered at doses that attenuated the exercise-induced decrease in plasma glutamine concentration.

Strenuous exercise decreases the percentage of type 1 T cells in the circulation.

Prolonged strenuous exercise is followed by a temporary functional immune impairment. Low numbers of CD4+ T helper (Th) and CD8+ T cytotoxic (Tc) cells are found in the circulation. These cells can be divided according to their cytokine profile into type 1 (Th1 and Tc1), which produce interferon-gamma and interleukin (IL)-2, and type 2 (Th2 and Tc2) cells, which produce IL-4. The question addressed in the present study was whether exercise affected the relative balance between the circulating levels of these cytokine-producing T cells. Nine male runners performed treadmill running for 2.5 h at 75% of maximal oxygen consumption. The intracellular expression of cytokines was detected following stimulation with ionomycin and phorbol 12-myristate 13-acetate in blood obtained before, during, and after exercise. The percentage of type 1 T cells in the circulation was suppressed at the end of exercise and 2 h after exercise, whereas no changes were found in the percentage of type 2 T cells. Plasma epinephrine correlated negatively with the percentage of circulating CD8+ T cells producing IL-2, whereas peak IL-6 correlated with the percentage of CD8+ IL-4-producing T cells in the circulation. Peak plasma IL-6 correlated with plasma cortisol postrunning. In conclusion, the postexercise decrease in T lymphocyte number is accompanied by a more pronounced decrease in type 1 T cells, which may be linked to high plasma epinephrine. Furthermore, IL-6 may stimulate type 2 T cells, thereby maintaining a relatively unaltered percentage of these cells in the circulation compared with total circulating lymphocyte number.

Effect of glutamine and protein supplementation on exercise-induced decreases in salivary IgA.

Postexercise immune impairment has been linked to exercise-induced decrease in plasma glutamine concentration. This study examined the possibility of abolishing the exercise-induced decrease in salivary IgA through glutamine supplementation during and after intense exercise. Eleven athletes performed cycle ergometer exercise for 2 h at 75% of maximal oxygen uptake on 3 separate days. Glutamine (a total of 17.5 g), protein (a total of 68.5 g/6.2 g protein-bound glutamine), and placebo supplements were given during and up to 2 h after exercise. Unstimulated, timed saliva samples were obtained before exercise and 20 min, 140 min, 4 h, and 22 h postexercise. The exercise protocol induced a decrease in salivary IgA (IgA concentration, IgA output, and IgA relative to total protein). The plasma concentration of glutamine was decreased by 15% 2 h postexercise in the placebo group, whereas this decline was abolished by both glutamine and protein supplements. None of the supplements, however, was able to abolish the decline in salivary IgA. This study does not support that postexercise decrease in salivary IgA is related to plasma glutamine concentrations.

Neural inhibition during maximal eccentric and concentric quadriceps contraction: effects of resistance training.

Despite full voluntary effort, neuromuscular activation of the quadriceps femoris muscle appears inhibited during slow concentric and eccentric contractions. Our aim was to compare neuromuscular activation during maximal voluntary concentric and eccentric quadriceps contractions, hypothesizing that inhibition of neuromuscular activation diminishes with resistance training. In 15 men, pretraining electromyographic activity of the quadriceps muscles [vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF)] was 17-36% lower during slow and fast (30 and 240 degrees/s) eccentric and slow concentric contractions compared with fast concentric contractions. After 14 wk of heavy resistance training, neuromuscular inhibition was reduced for VL and VM and was completely removed for RF. Concurrently, electromyographic activity increased 21-52, 22-29, and 16-32% for VL, VM, and RF, respectively. In addition, median power frequency decreased for VL and RF. Eccentric quadriceps strength increased 15-17%, whereas slow and fast concentric strength increased 15 and 8%, respectively. Pre- and posttraining median power frequency did not differ between eccentric and concentric contractions. In conclusion, quadriceps motoneuron activation was lower during maximal voluntary eccentric and slow concentric contractions compared with during fast concentric contraction in untrained subjects, and, after heavy resistance training, this inhibition in neuromuscular activation was reduced.

Exercise induces recruitment of lymphocytes with an activated phenotype and short telomeres in young and elderly humans.

This study was performed in order to investigate the type of T cells recruited to the blood in response to an acute bout of exercise with regard to mean lengths of telomeric terminal restriction fragments (TRF) and surface activation markers and with special emphasis on age-associated differences. Ten elderly and ten young humans performed maximal bicycle exercise. There was no difference in the number of recruited CD4+ and CD8+ cells between the young and elderly group. In both age groups the immediate increases could be ascribed to recruitment of CD28- cells (CD8+ and CD4+ cells) and memory cells (only CD8+ cells). Furthermore, after exercise mean TRF lengths were significantly reduced in blood mononuclear cells and in CD8+ cells from young subjects and in CD4+ cells from elderly subjects compared with lengths pre-exercise. These findings suggest that the mobilization of T lymphocytes during acute exercise is mainly a redistribution of previously activated cells with an increased replicative story than cells isolated from the blood at rest. Furthermore, elderly humans fulfilling the Senieur protocol have a preserved ability to recruit T lymphocytes in response to acute physical stress.

Dynamic balance during gait in children and adults with Generalized Joint Hypermobility.

BACKGROUND: The purpose of the study was to investigate if differences of the head and trunk stability and stabilization strategies exist between subjects classified with Generalized Joint Hypermobility and healthy controls during gait. It was hypothesized that joint hypermobility could lead to decreased head and trunk stability and a head stabilization strategy similar to what have been observed in individuals with decreased locomotor performance. METHODS: A comparative study design was used wherein 19 hypermobile children were compared to 19 control children, and 18 hypermobile adults were compared to 18 control adults. The subjects were tested during normal walking and walking on a line. Kinematics of head, shoulder, spine and pelvis rotations were measured by five digital video cameras in order to assess the segmental stability (angular dispersion) and stabilization strategies (anchoring index) in two rotational components: roll and yaw. FINDINGS: Hypermobile children and adults showed decreased lateral trunk stability in both walking conditions. In hypermobile children, it was accompanied with decreased head stability as the head was stabilized by the inferior segment when walking on a line. Several additional differences were observed in stability and stabilization strategies for both children and adults. INTERPRETATION: Stability of the trunk was decreased in hypermobile children and adults. This may be a consequence of decreased stability of the head. Hypermobile children showed a different mode of head stabilization during more demanding locomotor conditions indicating delayed locomotor development. The findings reflect that Generalized Joint Hypermobility probably include motor control deficits.

Variations in single fibre areas and fibre composition in needle biopsies from the human quadriceps muscle.

Cross-sectional area of a single fibres and the fibre distribution were measured for the two main types of fibres in needle biopsies from the quadriceps muscle of ten healthy young males. Methodological errors expressed as coefficient of variation (CV) of a single value for the area measurements were analysed and found to be 2.4% including the intraindividual error in handling the planimeter. An inhomogeneity in distribution and size of the fibres within the quadriceps muscle was indicated by a CV within the same section of 6-8% and between repeated biopsies of 15-20%.

Microphotometric determination of glycogen in single fibres of human quadriceps muscle.

A technique for the quantitation of glycogen in single fibres of human skeletal muscle is described. By using microphotometry the loss of glycogen from cryostat sections during a PAS-staining procedure was shown to be negligible. Further, it was found that nearly all the PAS-positive material (98.5%) inside a muscle fibre is glycogen. A significantly higher mean glycogen concentration (P less than 0.001) was found in type II fibres than in type I fibres in the resting quadriceps muscle of sedentary young males. The coefficient of variation for the glycogen concentration within each fibre type was found to be 17% and 15% for type I and type II respectively. The specificity of the PAS-staining technique for glycogen was confirmed by a statistically significant correlation (r = 0.78, P less than 0.001) between the glycogen concentration measured biochemically and that calculated from microphotometry and area and thickness measurements. With the technique described, it seems possible to measure the glycogen concentration of single muscle fibres in serial sections and to calculate this in standard biochemical terms.

Computerized tomographic determination of human thigh components. The effects of immobilization in plaster and subsequent physical training.

Thigh components were estimated by computerized tomography (CT) as well as by anthropometry in two healthy male soccer players (23--29 years), who for 5 weeks had one knee immobilized in a plaster of Paris. The investigations were performed on both thighs just after removal of the cast and after 5 weeks physical training of the inactivated quadriceps muscle. The different components were easily identified on a transverse scan through the middle of the thigh. The quadriceps muscle was 26% smaller after removal of the cast in the inactivated leg as compared with the contralateral leg; no differences were observed in the remaining thigh components. After rehabilitation a specific increase (22%) in the hypotrofic quadriceps muscle was observed, whereas no changes were disclosed in the remaining thigh components. The quadriceps muscle averaged 52% of the lean component in the uninjured thigh, and the subcutaneous part of the total cross-sectional area averaged 15%. The changes in the anthropometrically determined thigh components paralleled those observed by the CT scanning procedure. It is concluded that the loss in the lean thigh volume during immobilization in plaster cast is exclusively due to waste of the quadriceps muscle. CT scanning comprises a new valid tool to study changes in thigh components.

Force-velocity relationships in the human quadriceps muscles.

Isokinetic contraction were performed with the knee extensor muscles in 15 young male soccer players. The measurements were obtained by a modified isokinetic device (Orthotron). In the range of motion the angular velocity was constant from 90 degrees to 20 degrees of knee flexion. The angular velocity could be varied from 30 to 360 degrees/s. The overall variation of the pre-set speed and the peak torque, as estimated from duplicate trials through the whole velocity range, averaged 4% and 5%, respectively. The peak torque decreased linearly with increasing angular velocity in a semilogarithmic scale. An estimate of the peak torque-velocity relationship in an experimental subject was obtained from the slope and the fibre composition in the lateral portion of the quandriceps muscle in this group of subjects especially trained in fast movements. It was concluded that the present applied isokinetic device gives the opportunities to measure force-velocity characteristics in the intact quadriceps muscle of man.

Thickness measurements of skeletal muscle sections using the light microscope.

A new device is described for improving the accuracy of measuring the thickness of cryostat sections by the focusing technique in the light microscope. The necessity of such measurements is demonstrated by the great variation (range 2.55 micrometer--11.93 micrometer) in the thickness of serial cross-sections of frozen muscle biopsies from 12 healthy men. The final dehydration of the sections was found to reduce the thickenss of fresh sections by 47%. However, dehydration caused the cross-sectional area to be reduced by only 2.8%.

Lean and fat component of the human thigh. The effects of immobilization in plaster and subsequent physical training.

Changes in thigh components were investigated with the one-legged inactivity- and training-model using 22 young healthy male soccer players, who for 4-5 weeks had one leg immobilized in a cast. They were investigated before and after the cast period and after 4 weeks' physical training of the inactivated leg. Immobilization induced a significant increase in the subcutaneous thickness and a significant decrease in the circumference of the thigh (p less than 0.01). The calculated lean thigh volume was reduced from 4.93 1 to 4.10 1 (p less than 0.01), whereas the calculated fat thigh volume (1.5 1) was unchanged. The changes reversed after four weeks of progressive dynamic training, but did not reach the pre-immobilized values. Body weight decreased from 73.4 kg to 70.8 kg (p less than 0.01) during the immobilization period and was regained after the training period. The fat fraction of the body was unchanged. It is concluded that the loss in total thigh volume during inactivation in a cast is due to waste of the muscle tissue, and further that this loss is partly concealed by an unchanged fat thigh volume.

Cigarette smoking and maximal oxygen consumption rate in humans.

The relationship of maximal oxygen uptake with tobacco consumption was investigated in sixty-one young males. There was a significant negative correlation between daily consumption of tobacco and measured maximal oxygen uptake (Vo2max) expressed relative to body weight (r = -0.368, P less than 0.01) and to lean body mass (r = -0.497, P less than 0.001), respectively. No correlation could be demonstrated with regard to predicted maximal oxygen uptake (Vo3maxp). No difference was demonstrated between Vo2maxp and Vo2max in nonsmokers and heavy smokers, whereas Vo2maxp was significantly higher (P less than 0.01) in the group of moderate smokers than Vo2max. It is concluded that tobacco smoking decreases Vo2max even in young moderate smokers. Smoking habits should be considered among factors affecting Vo2maxp from cardiac frequency at submaximal levels.

Seasonal variation of maximal oxygen consumption rate in humans.

The relationship of maximal oxygen uptake (VO2 max) and resting oxygen uptake in two seasons of the year (winter/summer) was investigated in 119 young males. The subjects were conscripts, who were investigated at the calling-up time (winter: n = 58). The two groups were comparable with respect to their anthropometric data and smoking habits, as well as their occupational and leisure time activities. VO2 max was significantly (p less than 0.01) higher in the subjects investigated in the summer time (3.35 1/min) compared with those in the winter time (3.12 1/min). There was no difference in resting VO2 expressed relatively to body weight, whereas the resting VO2 was significantly (p less than 0.05) higher in winter than in summer, when it was expressed relatively to lean body mass and body surface area. The results suggest that seasonal variation in maximal aerobic power may occur in young males; this may in turn affect their response to physical training.

Progressive resistance exercise training of the hypotrophic quadriceps muscle in man. The effects on morphology, size and function as well as the influence of duration of effort.

The effects of progressive resistance exercise (PRE) training for 4 weeks on the hypotrophic quadriceps muscle were investigated in 23 young healthy male soccer players, who had been immobilized in a plaster cast 4-6 weeks after knee ligament injuries. The subjects were allocated to two training regimes where the injured leg was trained for periods of varying duration, whereas the intensity and frequency of exercise were alike in the two groups. However no significant differences were detected between the two training groups. In the whole material the lean thigh volume of the injured leg increased from 4.09 to 4.47 litres (p less than 0.001), whereas the fat component of the thigh was unchanged. The dynamic strength (1 RM) of the injured leg increased from 14.0 kg to 27.0 kg and amounted to 87% of the control leg after 4 weeks of training. At this time the maximum isometric strength amounted to 114 Nm, which was 63% of strength in the control leg. Succinate dehydrogenase (SDH) in homogenates of muscle biopsy sample increased (i.e. 20%, p less than 0.05) to the same level as found in the control leg. No changes in phosphofructokinase (PFK) were observed. The type I fibre distribution was lower in the immobilized leg than in the control leg. These results indicate that, following muscular hypotrophy resulting from 4-6 weeks of immobilization, dynamic exercise can restore the oxidative potential, whereas the size and strength are only partly recovered.