Showing papers in "European Journal of Applied Physiology in 1985"

The increase of perceived exertion, aches and pain in the legs, heart rate and blood lactate during exercise on a bicycle ergometer.

Abstract: This study was designed to show the general increase in perceived exertion, perception of aches or pain in the legs, heart rate (HR), and blood lactate, and the covariance between these variables during bicycle ergometer work, and to describe individual differences both within and between power levels by testing a large group (28 male students).

Linear increase in optimal pedal rate with increased power output in cycle ergometry

Abstract: This experiment was designed to estimate the optimum pedal rates at various power outputs on the cycle ergometer. Five trained bicycle racers performed five progressive maximal tests on the ergometer. Each rode at pedal rates of 40, 60, 80, 100, and 120 rev X min-1. Oxygen uptake and heart rate were determined from each test and plotted against pedal rate for power outputs of 100, 150, 200, 250, and 300 W. Both VO2 and heart rate differed significantly among pedal rates at equivalent power outputs, the variation following a parabolic curve. The low point in the curve was taken as the optimal pedal rate; i.e., the pedal rate which elicited the lowest heart rate or VO2 for a given power output. When the optimum was plotted against power output the variation was linear. These results indicate that an optimum pedal rate exists in this group of cyclists. This optimum pedal rate increases with power output, and when our study is compared to studies in which elite racers, or non-racers were used, the optimum seems to increase with the skill of the rider.

Serum hormones during prolonged training of neuromuscular performance

Abstract: The effects of a 24-weeks' progressive training of neuromuscular performance capacity on maximal strength and on hormone balance were investigated periodically in 21 male subjects during the course of the training and during a subsequent detraining period of 12 weeks. Great increases in maximal strength were noted during the first 20 weeks, followed by a plateau phase during the last 4 weeks of training. Testosterone/cortisol ratio increased during training. During the last 4 weeks of training changes in maximal strength correlated with the changes in testosterone/cortisol (P less than 0.01) and testosterone/SHBG (P less than 0.05) ratios. During detraining, correlative decreases were found between maximal strength and testosterone/cortisol ratio (P less than 0.05) as well as between the maximal strength and testosterone/SHBG ratio (P less than 0.05). No statistically significant changes were observed in the levels of serum estradiol, lutropin (LH), follitropin (FSH), prolactin, and somatotropin. The results suggest the importance of the balance between androgenic-anabolic activity and catabolizing effects of glucocorticoids during the course of vigorous strength training.

Human skeletal muscle fiber type alteration with high-intensity intermittent training

Abstract: The response of muscle fiber type proportions and fiber areas to 15 weeks of strenuous high-intensity intermittent training was investigated in twenty-four carefully ascertained sedentary (14 women and 10 men) and 10 control (4 women and 6 men) subjects. The supervised training program consisted mainly of series of supramaximal exercise lasting 15 s to 90 s on a cycle ergometer. Proportions of muscle fiber type and areas of the fibers were determined from a biopsy of the vastus lateralis before and after the training program. No significant change was observed for any of the histochemical charactertics in the control group. Training significantly increased the proportion of type I and decreased type IIb fibers, the proportion of type IIa remained unchanged. Areas of type I and IIb fibers increased significantly with training. These results suggest that high-intensity intermittent training in humans may alter the proportion of type I and the area of type I and IIb fibers and in consequence that fiber type composition in human vastus lateralis muscle is not determined solely by genetic factors.

All out anaerobic capacity tests on cycle ergometers. A comparative study on men and women.

Abstract: We have studied the effects of the braking force on the results of an anaerobic capacity test derived from the Wingate test (an all out 45 s exercise on a Monark 864 cycle ergometer against a given force at the fastest velocity from the beginning to the end of the test). Seven men and seven women participated in the study and performed a total of 63 all-out tests against different braking forces. The same subjects performed a force-velocity test on the same cycle ergometer. Since the relationship between force and velocity is approximately linear for peak velocities between 100 and 200 rev X min-1 (Peres et al. 1981a, b; Nadeau et al. 1983; Vandewalle et al. 1983) we characterized each subject by three parameters: P0 (the intercept of the force-velocity regression line with the force axis), V0 (the intercept of the regression line with the velocity axis) and Wmax (maximal power). The relationship between force and mean power was parabolic for the all-out anaerobic capacity test. In the present study the optimal force (the force giving the maximal value of mean power during an all out test) was higher for the men (approximately 1 N X kg BW-1) than the force proposed by others (0.853 N X kg BW-1 for Dotan and Bar-Or 1983). However, because of the parabolic relationship between force and mean power, the mean power which corresponds to the optimal force was approximately the same in both studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood flow in the emissary veins of the human head during hyperthermia.

Abstract: The direction of the blood flowing in the emissary veins (vena emissaria mastoidea and v. e. partietalis) was recorded in human subjects during moderate hyperthermia and hypothermia. During hyperthermia the blood flowed rapidly from skin to brain. During hypothermia either no flow could be detected or the blood flowed slowly from brain to skin. On two fresh cadavers the calvaria was removed with the scalp adhering. Gentle massaging of the scalp produced abundant drops of blood on the inner surface of the bone each time the scalp was massaged, thus showing that cutaneous blood can flow inward through the bone. These results support the hypothesis of selective brain cooling in hyperthermic humans by offering a possible mechanism.

Influence of Heat Stress and Acclimation on Maximal Aerobic Power

Abstract: Thirteen male volunteers performed cycle ergometer maximal oxygen uptake ( $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ tests) in moderate (21‡ C, 30% rh) and hot (49‡ C, 20% rh) environments, before and after a 9-day heat acclimation program. This program resulted in significantly decreased (P<0.01) final heart rate (24 bt·min−1) and rectal temperature (0.4‡ C) from the first to last day of acclimation. The $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ was lower (P 0.05) shown for maximal power output (PO max, watts) between environments either before or after acclimation. The $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ was higher (P<0.01) by 4% after acclimation in both environments. Also, PO max was higher (P<0.05) after acclimation in both the moderate (4%) and hot (2%) environments. The reduction in $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ in the hot compared to moderate environment was not related to the difference in core temperature at $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ between moderate and hot trials, nor was it strongly related with aerobic fitness level. These findings indicate that heat stress, per se, reduced the $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ . Further, the reduction in $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ due to heat was not affect be state of heat acclimation, the degree of elevation in core temperature, or level of aerobic fitness.

Activity of mono- and biarticular leg muscles during sprint running.

Abstract: A cinematographic recording of the movements of the lower limbs together with simultaneous emg tracings from nine lower limb muscles were obtained from two male track sprinters during three phases of a 100 m sprint run. The extensor muscles of the hip joint were found to be the primary movers by acceleration of the body's center of gravity (C.G.) during the ground phase of the running cycle. The extensors of the knee joint were also important in this, but to a minor extent, while the plantar flexors of the ankle joint showed the least contribution. The biarticular muscles functioned in a way different from the monoarticular muscles in the sense that they perform eccentric work during the flight and recovery phases and concentric work during the whole ground phase (support), whereas the monoarticular muscles are restricted first to eccentric work and then to concentric work during the ground phase. Furthermore, the biarticular muscles show variation (and rate of variation) in muscle length to a larger extent than the monoarticular muscles. Paradoxical muscle actions appear to take place around the knee joint, where the hamstring muscles, m. gastrocnemius, m. vastus laterialis and m. vastus medialis act as synergists by extending the knee joint during the last part of the ground phase.

Ventilatory anaerobic threshold in healthy children. Age and sex differences.

Abstract: The ventilatory anaerobic threshold (VAT) during graded exercise was defined as the oxygen uptake (\(\dot V_{{\text{O}}_{\text{2}} }\)) immediately below the exercise intensity at which pulmonary ventilation increased disproportionally relative to \(\dot V_{{\text{O}}_{\text{2}} }\). Since VAT is considered to be a sensitive and noninvasive measure for evaluating cardiorespiratoy endurance performance, the purpose of the present study was to determine normal values in children. We examined 257 healthy children (140 boys and 117 girls) varying in age from 5.7 to 18.5 years, during treadmill exercise. The data were analyzed in relation to sex and age. In boys the lowest \(\dot V_{{\text{O}}_{{\text{2max}}} }\) (ml · min−1 · kg−1) was found in the youngest age group (5–6 year). In girls, on the other hand, no significant increase occurred with age. For VAT, expressed as ml O2 · min−1 · kg−1 or as a percent of \(\dot V_{{\text{O}}_{{\text{2max}}} }\) a significant decrease was found in boys and girls with age. This suggests an increase in lactacid anaerobic capacity during growth. In contrast to observations in adults, only low correlations were found between \(\dot V_{{\text{O}}_{{\text{2max}}} }\) and VAT (r=0.28 in boys and r=0.52 in girls), which suggests that the development of the underlying physiological mechanism does not occur at the same rate in growing children. These data provide normal values for VAT that can be used for clinical exercise testing in the pediatric age group.

Responses of the lower limb to load carrying in walking man

Abstract: Muscle activity patterns of several lower limb muscles were examined in the left leg of normal human subjects walking at comfortable speed on a treadmill. In addition knee angular changes and the durations of the swing and stance phases of the step cycle were recorded. Data were collected during a period of normal control walking and when the subject carried a load, either in his right or left hand or on his back. Load (up to 20% of body weight) carried in either hand caused minimal changes in the kinematic parameters investigated but evoked significant prolongation of the normal ongoing electromyographic activity in the contralateral Gluteus medius and in the ipsilateral Gastrocnemius, Vastus lateralis and Semimembranosus. Load (up to 50% of body weight) carried on the back significantly shortened the swing phase and prolonged the ongoing electromyographic activity of the Vastus lateralis. These findings would seem to indicate that the activity of the leg musculature during walking is so tightly controlled that deviation from the normal kinematic pattern of the legs is largely prevented even when body posture and balance are disturbed by carrying substantial additional load.

Oxygen uptake kinetics in trained athletes differing in $$\dot V_{{\text{O}}_{{\text{2max}}} }$$

Abstract: Previous work has shown that when $$\dot V_{{\text{O}}_{\text{2}} }$$ kinetics are compared for endurance trained athletes and untrained subjects, the highly trained athletes have a faster response time. However, it remains to be determined whether the more rapid adjustment of $$\dot V_{{\text{O}}_{\text{2}} }$$ toward steady state in athletes is due to $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ differences or training adaptation alone. One approach to this problem is to study the time course of $$\dot V_{{\text{O}}_{\text{2}} }$$ kinetics at the onset of work in athletes who differ in $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ but have similar training habits. Therefore, the purpose of these experiments was to compare the time course of $$\dot V_{{\text{O}}_{\text{2}} }$$ kinetics at the onset of exercise in athletes with similar training routines but who differ in $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ . Ten subjects ( $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ range 50–70 ml · kg−1 · min−1) performed 6-minutes of cycle ergometer exercise at ∼50% $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ . Ventilation and gas exchange were monitored by open circuit techniques. The data were modeled with a single component exponential function incorporating a time delay, (T D ); $$\Delta \dot V_{{\text{O}}_{{\text{2}}f} } = \Delta \dot V_{{\text{O}}_{2ss} } {\text{ (1}} - e^{ - t - T_D /_{\tau )} }$$ , where Τ is the time constant $$\Delta \dot V_{{\text{O}}_{{\text{2}}f} }$$ is the increase in $$\dot V_{{\text{O}}_{\text{2}} }$$ at time t and $$\Delta \dot V_{{\text{O}}_{{\text{2ss}}} }$$ is the steady-rate increment above resting $$\dot V_{{\text{O}}_{\text{2}} }$$ . Kinetic analysis revealed a range of $$\dot V_{{\text{O}}_{\text{2}} }$$ half times from 21.6 to 36.0 s across subjects with a correlation coefficient of r=−0.80 (p<0.05) between $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ and $$\dot V_{{\text{O}}_{\text{2}} }$$ half time. These data suggest that in highly trained indicivuals with similar training habits, those with a higher $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ achieve a more rapid $$\dot V_{{\text{O}}_{\text{2}} }$$ adjustment at the onset of work.

Effects of L-carnitine loading on the aerobic and anaerobic performance of endurance athletes.

Abstract: l-Carnitine (l-c), a well known physiological carrier across the inner mitochondrial membrane of activated long chain fatty acids and acceptor of acyl groups from acyl-CoA, has been recently synthesised industrially. This has made it possible to study the effects ofl-c loading (4 g·d−1 by mouth over a period of 2 weeks) on the aerobic and anaerobic performance of 6 long distance competitive walkers. As a result of the treatment: 1) mean total, free and esterified seruml-c both at rest and shortly after completing a 120 min walk at about 65% of the individual maximal aerobic power\((\dot V_{O_{2\max } } )\) were significantly increased; 2)\(V_{O_{2\max } } \) increased 6%, from 54.5±3.7 (S.D.) to 57.8±47 mlO2·kg−1·min−1 (P<0.02); 3) blood lactate concentration (Lab) as a consequence of short bouts of repeated exercise (series of 10, 15 and 20 jumps off both feet on a force platform) was unchanged; 4) heart rate, pulmonary ventilation, oxygen consumption, and respiratory quotient in the same conditions as for 1) were unchanged. It is concluded that, in trained athletes, as a consequence ofl-c loading\(\dot V_{O_{2\max } } \) is slightly but significantly raised, probably as a result of an activation of substrate flow through the TCA cycle, whereas the lipid contribution to metabolism in prolonged submaximal exercise remains unchanged.

Effects of training at and above the lactate threshold on the lactate threshold and maximal oxygen uptake

Abstract: Thirty-three college women (mean age=21.8 years) participated in a 5 d·wk−1, 12 week training program. Subjects were randomly assigned to 3 groups, above lactate threshold (> LT) (N=11; trained at 69 watts above the workload associated with LT), =LT (N=12; trained at the work load associated with LT) and control (C) (N=10). Subjects were assessed for \(\dot V_{O_{2\max } } \), \(\dot V_{O_2 } \)LT, \(\dot V_{O_2 } \)LT/\(\dot V_{O_{2\max } } \), before and after training, using a discontinuous 3 min incremental (starting at 0 watts increasing 34 watts each work load) protocol on a cycle ergometer (Monark). Respiratory gas exchange measures were determined using standard open circuit spirometry while LT was determined from blood samples taken immediately following each work load from an indwelling venous catheter located in the back of a heated hand. Body composition parameters were determined before and after training via hydrostatic weighing. Training work loads were equated so that each subject expended approximately 1465 kJ per training session (Monark cycle ergometer) regardless of training intensity. Pretraining, no significant differences existed between groups for any variable. Post training the > LT group had significantly higher \(\dot V_{O_{2\max } } \) (13%), \(\dot V_{O_2 } \) (47%) and \(\dot V_{O_2 } \)LT/\(\dot V_{O_{2\max } } \) (33%) values as compared to C (p LT group showed a significant increase in \(\dot V_{O_2 } \) (48%) (p LT group showed significant increases in \(\dot V_{O_2 } \)LT/\(\dot V_{O_{2\max } } \) (= LT 16%, > LT 42% (p<.05)). No differences were found between or within groups post training for body composition parameters. It was concluded that training above the LT results in an improvement in \(\dot V_{O_2 } \)LT and that large improvements in \(\dot V_{O_{2\max } } \) may not be required for large improvements in \(\dot V_{O_2 } \).

Variations in iron status with fatigue modelled from training in female distance runners.

Abstract: A low hemoglobin level or even frank anemia is common among female endurance runners; controversy presently exists on the effectiveness of iron supplementation. In the past inadequate descriptions of training and too infrequent measurement of iron indices over a sufficiently long period, have made it difficult to establish any relationship between iron status and training upon which to base a rational iron therapy. In this study 5 young women distance runners age 18–25 years have been studied for 300 days. A numerical index was used to quantify the extent of an individual's daily training effort and a conceptual model of the effect of training allowed definition of the extent of consequent fatigue, to be calculated. Red blood cell number and hemoglobin concentration were measured regularly throughout, and during the last 200 days serum iron, ferritin, total iron binding capacity and percent transferrin saturation were also measured. It has been shown in most subjects that serum iron and transferrin saturation varied in phase with training and the fatigue index, throughout the period while serum ferritin varied out of phase. It is suggested that supplementing iron intake may be of little use during heavy training and concomitant high fatigue because transferrin saturation is also very high at this time and ineffective in promoting absorption of dietary iron.

The effect of exercise on the production and clearance of testosterone in well trained young men

Abstract: Tritium-labelled testosterone was infused into four well-trained subjects at rest and during one hour of exercise at about 60% of their maximum aerobic power. This exercise regime led to a mean increase of 27% (range 10–51%) in plasma testosterone concentration. At the same time there were significant decreases in the estimated hepatic plasma flow (EHPF) (45%; range 28–67%), metabolic clearance rate of testosterone (MCRT) (29%; range 18–37%) and plasma volume (8.2%; range 3–10%). The production rate of testosterone decreased by 10% (range 9–22%) but this was not statistically significant. The ratio MCRT: EHPF increased in 3 out of 4 subjects in response to exercise but there was considerable inter-subject variation both at rest and during exercise. These findings suggest that the exercise-induced elevation of testosterone level is due solely to the reduction in the rate at which testosterone is cleared from the plasma. The principal cause of the reduction in MCRT is probably the reduction in EHPF but the variation in the ratio MCRT: EHPF suggests that changes in the extrahepatic clearance of testosterone may also be involved.

Noninvasive determination of the anaerobic threshold in canoeing, cross-country skiing, cycling, roller, and iceskating, rowing, and walking

Abstract: The relationship between velocity (V) and heart rate (HR) was determined in four canoeists, 42 cross-country skiers, 73 cyclists, nine ice-skaters, 10 roller-skaters, 32 rowers, and 20 walkers. The athletes were asked to increase their work intensity progressively, from low to submaximal velocities; HRs were determined by ECG in roller-, ice-skating, and walking, or read on a cardiofrequency meter in canoeing, cross-country skiing, cycling, and rowing. In all the athletes examined the linearity of the V-HR relationship was maintained up to a submaximal speed (deflection velocity, Vd), beyond which the increase in work intensity exceeded the increase in HR. Vd and anaerobic threshold (AT), determined through blood lactate measurements, were coincident in 19 athletes (6 cross-country skiers, 3 cyclists, 2 roller-skaters, 3 rowers, and 5 walkers). Vd was correlated with the average speeds maintained in walking (20 km, n = 13, r = 0.88), cross-country skiing (15 km, n = 20, r = 0.80; 30 km, n = 8, r = 0.82; 12 km, n = 7, r = 0.86; 11 km, n = 7, r = 0.86) and cycling (1,000 m flying-start, n = 68, r = 0.83), thus showing that AT is a limiting factor in these aerobic events.

Effect of coupling the breathing- and cycling rhythms on oxygen uptake during bicycle ergometry

Abstract: The influence of the degree of coupling between the breathing and cycling rhythms (K) on oxygen uptake $$\dot V_{O_2 } $$ was examined in 30 volunteers. They cycled on an ergometer with a load equal to 50% of their work capacity 170 in two experimental runs with spontaneous breathing rhythm, and in a further two runs with acoustically triggered breathing. K was continuously ascertained. $$\dot V_{O_2 } $$ and other respiratory parameters were measured by an automatic “breath-by-breath analysis” system. In 16 subjects, $$\dot V_{O_2 } $$ -differences between runs were correlated with the differences in K. In the majority of these subjects (12), $$\dot V_{O_2 } $$ decreased significantly with increasing K. In 14 subjects, $$\dot V_{O_2 } $$ -and K-variations within individual runs were analyzed. Phases with higher K were regularly accompanied by a decrease in $$\dot V_{O_2 } $$ . It is concluded that coupling the breathing and cycling rhythms reduces $$\dot V_{O_2 } $$ for a given moderate work load, although the magnitude of the $$\dot V_{O_2 } $$ -reduction varies considerably between individuals.

Nutritional alterations at high altitude in man

Abstract: During the French 1980 Mount Pabil (7,102 m) Expedition, a study was made of four altitude-acclimatised climbers (age 36.5±3.6 years; $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ 50.5±3.1 ml · kg−1). Intake of various nutrients, body weight, skinfold thicknesses as indices of body composition, and water and nitrogen balances, were recorded before, and during high altitude exposure, and again after the return to low altitude. There was a significant (35–57%) reduction in total caloric intake at high altitude. Body weight decreased progressively, mainly due to a reduction in body fat. The subjects apparently remained in water balance, while the nitrogen balance was always negative during high altitude exposure. The significant nutritional alterations were mainly observed above 6,000 m. They are discussed with respect to changes in feeding patterns and in hormonal status of the climbers accompanying hypoxia and other stressors proper to high altitude.

Efficiency of sweat evaporation in unacclimatized man working in a hot humid environment.

Abstract: A method is devised where evaporation and dripping sweat rates can be continuously determined during work 6 unacclimatized men performed work on a bicycle ergometer at 3 different workloads and in 3 humidities Ambient temperatures were always equal to mean skin temperatures, thus eliminating all sensible heat transfer Evaporation rates ranged between 68 and 112 g · min−1 Rates of dripping sweat ranged from a mean of 22 to 104 g · min−1 One subject dripped 203 g · min−1 in condition H3 (70% RH, 100 W) The fully wet skin in condition H3 corresponded to an evaporative heat transfer coefficient of 99 W · m−2 kPa Efficiency of sweating, defined as the ratio between secreted and evaporated sweat, ranged from 87 (50% RH, 50 W) to 51% (70% RH, 100 W) Corresponding values of wettedness were 056 and 10 Efficiency fell to 51% for fully wet skin (H3), and in some subjects the efficiency values were remarkably low One subject displayed an efficiency of 31% in condition H3 The reduction in efficiency at a given level of wettedness was higher than previously reported

Plasma FFA responses to prolonged walking in untrained men and women

Abstract: Gender differences in plasma FFA responses to 90 min of treadmill walking at 35% \(\dot V_{{\text{O}}_{{\text{2max}}} }\)were investigated in six men and six women following an overnight fast. The subjects represented average values for maximal oxygen uptake and body fat percentage for age and gender. Mean plasma FFA concentration at 45 and 90 min of exercise were significantly (P<0.05) higher for women (0.82 mmol·l−01, 0.88 mmol·l−01) than men (0.42 mmol·l−01, 0.59 mmol·l−1). Lower R values for women throughout the exercise period indicated a greater percentage fat in total metabolism than for men while the FFA/glycerol results supported greater lipolytic activity for women. The uniformity of percent fat in metabolism for women from rest to exercise showed that FFA release from adipose tissue increased rapidly with the onset of exercise which was not the case for men. Comparison of metabolic data as well as a statistical analysis (ANCOVA) controlling for the influence of \(\dot V_{{\text{O}}_{{\text{2max}}} }\)and percentage body fat on FFA plasma concentration suggested that gender differences in FFA responses to prolonged submaximal exercise can be expected to occur in untrained subjects.

Alignment of the human body in standing.

Abstract: Alignment of the body in typical symmetrical standing was studied by photographing fifteen subjects in profile on a reaction board. Two aspects of alignment were studied: (1) the anteroposterior position of the body landmarks of knee joint, hip joint, shoulder joint, and ear, compared to the ankle joint; and (2) the positions of the partial centers of gravity above the knee and hip, as a measure of how the body is balanced above these joints.

Transfer effects in endurance exercise. Adaptations in trained and untrained muscles.

Abstract: The effects of 8 weeks of bicycle endurance training (5 x /week for 30 min) on maximal oxygen uptake capacity ( $$\dot V_{O_{2max} } $$ ) during arm and leg ergometry, and on the ultrastructure of an untrained arm muscle (m. deltoideus), and a trained leg muscle (m. vastus lateralis) were studied. With the training, leg- $$\dot V_{O_{2max} } $$ for bicycling increased by +13%, while the capillary per fiber ratio and the volume density of mitochondria in m. vastus lateralis increased by +15% and +40%, respectively. In contrast, the untrained m. deltoideus showed an unchanged capillary per fiber ratio and a decreased mitochondrial volume density (−17%). Despite this decrease of mitochondrial volume arm- $$\dot V_{O_{2max} } $$ increased by +9%. It seems unlikely that the observed discrepancy can be explained by cardiovascular adaptations, since arm cranking did not fully tax the cardiovascular system (arm- $$\dot V_{O_{2max} } $$ /leg- $$\dot V_{O_{2max} } $$ : 0.74 and 0.71 before and after training, respectively). Thus neither cardiovascular adaptations nor local structural changes in the untrained muscles could explain the increased arm- $$\dot V_{O_{2max} } $$ . However, the enhanced capacity for lactate clearance after endurance training could be sufficient to account for the larger $$\dot V_{O_{2max} } $$ during arm cranking. We propose that an increased net oxidation of lactate might be responsible for the increased arm- $$\dot V_{O_{2max} } $$ found after bicycle endurance training.

The relationship between lactate and ventilatory thresholds: coincidental or cause and effect?

Abstract: To determine if blood lactate (LA) is the stimulus responsible for ‘breakaway’ ventilation (VE), the lactate (LT) and ventilation (VT) thresholds were monitored during one-legged cycling exercise. Ten healthy volunteer male subjects (Mean 2-legged \(\dot V_{O_{2\max } } \) =4.27 l·min−1) performed prior exercise (PE) to reduce muscle glycogen stores by cycling at 75–85% of maximal heart rate (HR max) for 60–75 min, followed by a 30 h low carbohydrate diet. Pre- and post- LT and VT tests were performed on a cycle ergometer employing a continuous protocol with increments of 16 W every 3 min. Muscle biopsies were taken from the vastus lateralis muscle before the PE ride, prior to the threshold test 24 h later, and before testing the non-exercised (NE) leg. An I.V. catheter placed in the antecubital vein was used for serial blood samples taken at rest, and during the final 30 s of each progressive load. Gas analysis was calculated every 30 s (Beckman Metabolic Measurement Cart). Biopsies (N=3) showed that the exercise and diet regimen elicited glycogen reduction which significantly (p<0.05) reduced R and the blood LA concentration in both the PE (2.62 to 1.99 mmol·l−1) and NE (2.87 to 2.26 mmol·l−1) legs at LT. At VT, LA concentrations were also significantly reduced in the PE (3.35 to 2.56 mmol·l−1) and NE (3.59 to 2.74 mmol·−1) legs. \(\dot V_{O_2 } \) and VE, however, were similar between pre- and post- tests. Results of this study suggest that plasma LA accumulation is not responsible for ‘breakaway’ ventilation during progressive exercise and that LT and VT are not a cause and effect relationship.

Plasma testosterone and catecholamine responses to physical exercise of different intensities in men.

Abstract: Plasma testosterone, noradrenaline, and adrenaline concentrations during three bicycle ergometer tests of the same total work output (2160 J·kg−1) but different intensity and duration were measured in healthy male subjects. Tests A and B consisted of three consecutive exercise bouts, lasting 6 min each, of either increasing (1.5, 2.0, 2.5 W·kg−1) or constant (2.0, 2.0, 2.0 W·kg−1) work loads, respectively. In test C the subjects performed two exercise bouts each lasting 4.5 min, with work loads of 4.0 W·kg−1. All the exercise bouts were separated by 1-min periods of rest.

Effects of dietary sodium on body and muscle potassium content during heat acclimation.

Abstract: It has been suggested that renal conversion of sodium (Na+) during training in hot environments results in potassium (K+) deficiencies. This investigation examined the influence of two levels of dietary Na+ intake (399 vs 98 mmol X d-1) on intramuscular, urinary, sweat, and whole body K+ homeostasis. Nine unacclimated, untrained males underwent heat acclimation during two 8 day dietary-exercise regimens (40.1 +/- 0.1 degrees C, 23.5 +/- 0.4% RH). Both diets resulted in depressed urinary K+ excretion. Sweat K+ and muscle K+ concentrations were not altered by diets or acclimation. The whole body stores of Na+ increased 31.1% (+916.8 mmol) during the high Na+ diet and decreased 7.8% (-230.4 mmol) during the low Na+ diet; whole body stores of K+ increased 4.1% (+137.6 mmol) during the high Na+ diet and increased 3.4% (+113.6 mmol) during the low Na+ diet. This dietary-acclimation protocol did not result in whole-body or intramuscular K+ deficits and offers no evidence to support previous claims that dietary sodium levels affect K+ balance.

Comparison of office chairs with fixed forwards or backwards inclining, or tiltable seats.

Abstract: Three adjustments of an office chair seat: — one inclining +10‡ (forwards), one inclining − 5‡ (backwards), and one being freely tiltable from −8‡ to +19.5‡ — were investigated using two groups of healthy female workers in a field (n=12), and a laboratory study (n=10), respectively. The seat adjustments were examined with regard to effects on foot swelling, lumbar muscular load, backrest pressure and subjective acceptability. Desk-work and typing were compared according to lumbar muscular activity, seat movements (tiltable seat), and backrest pressure. Foot swelling tended to increase with increasing seat height but was not influenced by the ability to tilt the seat or not. With the different seat adjustments lumbar muscular activity did not change systematically in spite of greater backrest pressure when the seat inclined backwards. The tiltable seat was preferred to the others. Typing was associated with a more constrained and tens posture than desk work, because movements, transferred to the tiltable seat, decreased and the muscular load increased. Backrest pressure was highest during typing. A tendency towards gradually increasing restlessness (i. e. seat movements) and increasing forward inclination of the tiltable seat with time was observed.

Serum creatine kinase activity following forearm flexion isometric exercise

Abstract: The purpose of this study was to 1) compare serum creatine kinase (CK) activity following two forearm flexion isometric exercise regimens differing in work to rest ratio, and 2) examine the CK response to a repeated bout of isometric exercise. Eleven males were tested on two sessions (bouts) spaced 1 week apart. For bout 1, five subjects (group A) performed a forearm flexion isometric exercise consisting of 40 10-s maximal contractions with 20-s inter-trial rests (10∶20), while six (group B) performed 40 maximal 10-s contractions with 5-s inter-trial rests (10∶5). The increase in serum CK activity following the 10∶20 exercise (143%) was significantly greater than that following the 10∶5 exercise (52%). The 10∶20 exercise was also associated with greater tension generation over trials. One week later, both groups performed a bout of 10∶20 exercise. A substantial reduction in the serum CK response was found following this second bout. The data suggest that for bout 1 the isometric exercise associated with the greater overall tension levels resulted in the greater CK response. However, when the 10∶20 exercise was repeated 1 week later, a substantial reduction in the CK response was found which was unrelated to the tension generated.

Muscle glycogen depletion during exercise at 9‡ C and 21‡ C

Abstract: This study compared glycogen depletion in active skeletal muscle after light and moderate exercise in both cold and comfortable ambient conditions Twelve male subjects (Ss) were divided into two groups equally matched for the submaximal exercise intensity corresponding to a blood lactate concentration of 4 mM (W4) during cycle exercise On two separate days Ss rested for 30 min at ambient temperatures of either 9‡ C or 21‡ C, with the order of temperature exposure being counter-balanced among Ss Following rest a tissue specimen was obtained from the m vastus lateralis with the needle biopsy technique Six Ss then exercised on a cycle ergometer for 30 min at 30% W4 (range=50–65 W) while the remaining group exercised at 60% W4 (range=85–120 W) Another biopsy was taken immediately after exercise and both samples were assayed for glycogen content Identical procedures were repeated for the second environmental exposure No significant glycogen depletion was observed in the Ss exercising at 30% W4 in 21‡ C, but a 23% decrease (p=004) was observed when the same exercise was performed at 9‡ C A 22% decrease (p=0002) in glycogen occurred in the 60% W4 group at 21‡ C, which was not significantly different from that observed during the same exercise at 9‡ C The results suggest that muscle substrate utilization is increased during light exercise in a cold environment as compared to similar exercise at a comfortable temperature, probably due to shivering thermogenesis Heat produced with higher exercise intensities seems to be sufficient to prevent shivering and the accompanying glycogenolysis

The influence of muscle metabolic characteristics on physical performance.

Abstract: This study describes the influence of muscle fiber type composition, enzyme activities and capillary supply on muscle strength, local muscle endurance or aerobic power and capacity. Muscle biopsies were obtained from m. vastus lateralis in thirteen physically active men. Histochemical staining procedures were applied to assess the percentage of fast twitch (FT) fibers, muscle fiber area, and capillary density. Also, the activity of citrate synthase (CS), creatine kinase (CK), hexokinase (HK), lactate dehydrogenase (LDH), and phosphofructokinase (PFK) were analysed using fluorometrical assays. Peak torque at ‘low’ and ‘high’ angular velocities was measured during leg extension. Similarly, muscle fatigue (e. g. peak torque decline) and recovery from a short-term exercise task were measured during maximal, voluntary consecutive leg extensions. Aerobic power ( $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ ) and aerobic capacity (e.g. onset of blood lactate concentration; OBLA), as defined by a blood lactate concentration of 4 mol · l−1 were measured during cycling. Peak torque at a high angular velocity was positively correlated with % FT area (p<0.001). Fatigue and recovery were correlated with LDH · CS−1 (p<0.001). WOBLA was best correlated with PFK and PFK · CS−1 (p<0.001). Hence, muscle strength was partly determined by fiber type composition whereas local muscle endurance, recovery and aerobic capacity reflect mainly capillary supply and the activity of key enzymes involved in aerobic and anaerobic metabolism.

Energy sources in alpine skiing (giant slalom)

Abstract: The energy cost of a giant slalom event was measured in eight skiers of national level. The lap lasted on average 82 s. \(\dot V_{{\text{O}}_{\text{2}} }\)was measured during the first, the second and the last third of the lap in different trials and also during recovery from a complete lap. Blood lactate was measured at the end of a lap. From the data obtained it was possible to calculate that: a) \(\dot V_{{\text{O}}_{\text{2}} }\), as measured during the lap, would correspond at steady state to 80% of the \(\dot V_{{\text{O}}_{{\text{2max}}} }\)of the subjects; b) the total metabolic power delivered during the lap should be equal to about 72ml O2·kg−1·min−1, corresponding to 120% of \(\dot V_{{\text{O}}_{{\text{2max}}} }\)of the subjects. Considering the short duration of the trial and the power output delivered during maximal efforts on a bicycle ergometer, it appears that the giant slalom is not a very high energy demanding event.