Showing papers in "European Journal of Applied Physiology in 1983"

A simple method for measurement of mechanical power in jumping.

Abstract: A simple test for the measurement of mechanical power during a vertical rebound jump series has been devised. The test consists of measuring the flight time with a digital timer (+/- 0.001 s) and counting the number of jumps performed during a certain period of time (e.g., 15-60 s). Formulae for calculation of mechanical power from the measured parameters were derived. The relationship between this mechanical power and a modification of the Wingate test (r = 0.87, n = 12 males) and 60 m dash (r = 0.84, n = 12 males) were very close. The mechanical power in a 60 s jumping test demonstrated higher values (20 W X kgBW-1) than the power in a modified (60 s) Wingate test (7 W X kgBW-1) and a Margaria test (14 W X kgBW-1). The estimated powers demonstrated different values because both bicycle riding and the Margaria test reflect primarily chemo-mechanical conversion during muscle contraction, whereas in the jumping test elastic energy is also utilized. Therefore the new jumping test seems suitable to evaluate the power output of leg extensor muscles during natural motion. Because of its high reproducibility (r = 0.95) and simplicity, the test is suitable for laboratory and field conditions.

Skeletal muscle tension, flow, pressure, and EMG during sustained isometric contractions in humans.

Abstract: In five healthy males sustained isometric torques during elbow flexion, knee extension, and plantar flexion correlated positively with intramuscular tissue pressure (MTP) in the range 0–80% of the maximal voluntary contraction (MVC). During passive compression of the muscle at rest 133-Xenon muscle clearance stopped when MTP reached diastolic arterial pressure (DAP) indicating that the muscle vascular bed was occluded. However, during sustained contractions this relation between DAP, flow and MTP was not seen. In two cases 133-Xenon clearance from M. soleus did not stop in spite of an 80% maximal contraction and MTP stayed below DAP. In other cases MTP would reach as high as 240 mm Hg before clearance was zero. In the deeper parts of the muscles MTP during contraction was increased in relation to the more superficial parts. The mean values for the %MVC that would stop MBF varied between 50 and 64% MVC for the investigated muscles. Mean rectified EMG (MEMG) showed a high correlation to MTP during sustained exhaustive contractions: When MEMG was kept constant MTP also remained constant while the exerted force decreased; when force was kept constant both MEMG and MTP increased in parallel. This demonstrated that muscle tissue compliance is decreasing during fatigue. Muscle ischemia occuring during sustained isometric contractions is partly due to the developed MTP, where especially the MTP around the veins in the deeper parts of the muscle can be considered of importance. However, ischemia is also affected by muscle fiber texture and anatomical distorsion of tissues.

Load optimization for the wingate anaerobic test

Abstract: The purpose of the present study was to define the optimal loads (OL) for eliciting maximal power-outputs (PO) in the leg and arm modes of the 30s Wingate Anaerobic Test (WAnT). Eighteen female and seventeen male physical education students, respectively 20.6 +/- 1.6 and 24.1 +/- 2.5 years old, volunteered to participate. In each of the total five sessions, the test was administered twice on a convertible, mechanically braked cycle-ergometer, once for the legs and once for the arms. The five randomized, evenly-spaced resistance loads ranged from 2.43 to 5.39 Joule per pedal revolution per kg body weight (B. W.) for the legs, and from 1.96 to 3.92 for the arms. The measured variables were mean (MP x kg-1) and peak PO as well as absolute and relative measures of fatigue. A parabola-fitting technique was employed to define the optimal loads from the MP x kg-1 data. The resulting OL were 5.04 and 5.13 Joule x Rev-1 x kg B.W.-1 in the leg and 2.82 and 3.52 in the arm tests for the women and men, respectively. OL were shown to depend on PO magnitude. However, within a two-load span (0.98 Joule x Rev-1 x kg B.W.-1) about the OL, MP x kg-1 did not vary by more than 1.4% in the leg and 2.2% in the arm tests. It is suggested that although the WAnT is rather insensitive to moderate variation in load assignment, improved results could be obtained by using the stated OL as guidelines that may be modified according to individual body build, composition, and, particularly, anaerobic fitness level.

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

Abstract: 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 005) 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 005) 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

Specificity of velocity in strength training.

Abstract: Twenty-one male volunteers (ages 23–25 years) were tested pre- and post training for maximal knee extension power at five specific speeds (1.05, 2.09, 3.14, 4.19, and 5.24 rad·s−1) with an isokinetic dynamometer. Subjects were assigned randomly to one of three experimental groups; group S, training at 1.05 rad·s−1 (n=8), group I, training at 3.14 rad·s−1 (n=8) or group F, training at 5.24 rad·s−1 (n=5). Subjects trained the knee extensors by performing 10 maximal voluntary efforts in group S, 30 in group I and 50 in group F six times a week for 8 weeks. Though group S showed significant increases in power at all test speeds, the percent increment decreased with test speed from 24.8% at 1.05 rad·s−1 to 8.6% at 5.24 rad·s−1. Group I showed almost similar increment in power (18.5–22.4 at all test speeds except at 2.09 rad·s−1 (15.4%). On the other hand, group F enhanced power only at faster test speeds (23.9% at 4.19 rad·s−1 and 22.8% at 5.24 rad·s−1).

A work-energy approach to determine individual joint contributions to vertical jump performance

Abstract: A work-energy approach was used to determine the contributions of the muscles crossing the hip, knee and ankle joints to the total positive work done during maximal vertical jumps. It was found that the average relative contributions of the ankle and hip muscles were approximately 23 and 28% respectively, with the remaining 49% of the work being done by the muscles acting at the knee joint. The efficiency of jumping, i.e. the ratio of potential energy gained to the net mechanical work done by the muscles acting at the three lower limb joints was nearly 1.0. These results stress the importance of all three major leg extensor muscle groups to the performance of an explosive activity such as vertical jumping. It is suggested that the work-energy approach supplies useful information concerning joint contributions without the problems associated with other techniques.

Mechanical power test and fiber composition of human leg extensor muscles.

Abstract: The present study was undertaken to assess the relationship between the mechanical power developed during new anaerobic power test and muscular fiber distribution. Ten track and field male athletes were used as subjects, whose muscle fiber composition (m. vastus lateralis) varied from 25 to 58 fast twitch (FT) fibers. The test consisted of measuring the flight time with a special timer during 60 s continuous jumping. A formula was derived to allow the calculation of mechanical power during a certain period of time (e.g., in the present study every 15 s during 60 s of jumping performance). The relationship between the mechanical power for the first 15 s period correlated best with fast twitch (FT) fiber distribution (r = 0.86, p less than 0.005). However, the power output during the successive 15 s periods demonstrated lower correlation with FT, and this relationship became statistically non-significant after 30 s of work. The sensitivity to fatigue of the test was supported by the relationship observed between the decrease of power during 60 s jumping performance and the percentage of FT fibers (r = 0.73, p less than 0.01). Thus, the present findings suggest that muscular performance, as determined by the new jumping test, is influenced by skeletal muscle fiber composition. The new test, which primarily evaluates maximal short term muscular power, also proved sensitive in assessing fatigue patterns during 60 s of strenuous work.

Energy cost of treadmill and floor walking at self-selected paces

Abstract: Oxygen uptake-velocity regression equations were developed for floor and level treadmill walking by having two groups of men, aged 19-29 years (n = 20) and 55-66 years (n = 22), walk at four self-selected paces, from "rather slowly" to "as fast as possible". A two-variable quadratic model relating VO2 (ml X kg-1 X min-1) to velocity (m X s-1) was adopted for prediction purposes. However, age and fatness significantly (P less than 0.05) interacted with treadmill walking speed, while age alone significantly interacted with floor speed. In addition, a significant difference was found between the energy cost of floor and treadmill walking. For example at the normal walking speed of 1.33 m X s-1, the energy cost for the treadmill (age 55-66 years) was 10.58 ml X kg-1 X min-1 and for the floor, 11.04 ml X kg-1 X min-1 (P less than 0.05). Four quadratic equations are therefore presented, one each for floor and treadmill in each of the two age-groups. The percent variance explained was between 87 and 95% for each of these equations.

Changes in blood ammonia, lactate and amino acids in relation to workload during bicycle ergometer exercise in man

Abstract: Whole body exercise at intensities up to 50% \(\dot V\)O2max has no effect on the concentration of blood ammonia but a threefold rise in blood ammonia is observed at workloads up to maximal. There is a linear relationship between blood ammonia and lactate production during exercise which suggests that the two processes may be linked to a common process of short-term energy provision. Blood glutamine and blood alanine both show rises linearly related to power output during exercise, suggesting that if these amino acids are sinks for ammonia then the process of ammonia incorporation is saturated at high workloads.

Relationships between muscle strength and muscle cross-sectional area in male sprinters and endurance runners

Abstract: The relationship between the cross-sectional area (CSA) and maximum voluntary isometric strength of the knee extensor muscles was measured in a group of untrained subjects (control group, n=30), a group of successful marathon runners (n=6) and a group of successful sprinters (n=6). All subjects were male, aged between 20 and 41 years. In the control group muscle strength was found to be positively correlated with lean body mass (p<0.01) and with muscle CSA as determined by computed tomography scanning of the leg at mid-thigh level (p<0.001). However, in spite of these significant relationships, there was considerable variability between subjects. The sprinters were significantly stronger than the endurance runners (p<0.01), but neither of the athletic groups differed significantly from the control group. Muscle CSA was greater in the sprinters than in the marathon runners but this difference was not significant. The ratio of muscle strength to CSA in the control group varied from 7.07 to 13.57. All the trained subjects fell within this normal range, but the sprinters' muscles were stronger per unit CSA than the muscles of the marathon runners (p<0.05). Since it is well established that the leg muscles of sprinters contain a high proportion of fast twitch (FT) muscle fibres whereas endurance runners have a high proportion of slow twitch (ST) fibres, these results suggest that the strength which can be produced by a muscle may depend on its fibre composition. Variation in the distribution of the different fibre types in the untrained population may therefore account at least in part for the wide variability observed in this group.

Relationships between muscle fibre conduction velocity and frequency parameters of surface EMG during sustained contraction

Abstract: A surface electrode array has been used to investigate the relationship between muscle fibre conduction velocity and the frequency spectrum during sustained isometric contractions of the biceps brachii. Measurement of muscle fibre conduction velocity was made directly, using the zero-crossing time delay method with two pairs of bipolar electrodes. It was found that the average conduction velocity during an intense (12 kg) sustained contraction decreased by about 20% at the end of the contracting period. Except for peak frequency, changes in the spectral parameters decreased in a similar manner. These results indicate that, during fatiguing contraction, spectral modifications are partly due to reduction in the action potential conduction velocity along the muscle fibres.

A comparison of the contractile properties of the human gastrocnemius and soleus muscles.

Abstract: Twitch speeds and potentiating capacities have been determined for human medial and lateral gastrocnemius and soleus muscles. The experiments involved and application of submaximal stimuli to the respective muscle bellies, with monitoring of the evoked compound action potentials (M-waves) during repetitive stimulation. Contrary to an earlier report, the lateral gastrocnemius was found to have a significantly shorter mean contraction time (100.0 +/- 10.8 ms) than the soleus (156.5 +/- 14.7 ms) and this value was also significantly different from that of the medial gastrocnemius (113.7 +/- 19.6 ms). The mean half-relaxation time for each muscle also differed significantly from those for the other two muscles. A further contrast between the muscles was that potentiation of the twitch, following a 3-s tetanus at 50 Hz, was significantly greater in the lateral gastrocnemius than in soleus (mean values 60.4 +/- 43.1% and 2.6 +/- 3.3% respectively.

Relationships of anaerobic threshold and onset of blood lactate accumulation with endurance performance

Abstract: This study was undertaken to compare the contribution of both the anaerobic threshold (AT) and onset of blood lactate accumulation (OBLA) with endurance performance in eleven non-endurance trained active male adults. AT determination was based upon both blood lactate and gas exchange criteria, while OBLA was determined as the point corresponding to a blood lactate concentration of 4 mmol·l−1. A dependent t-test revealed significantly higher values for OBLA related variables as compared with corresponding AT related variables, thereby validating the comparison of these two categories of variables in relation to endurance performance. Approximately 67, 60, 37, and 50% of the variance in endurance performance were accounted for by \(\dot V\)O2 (ml · kg−1 · min−) AT-WR, OBLS-\(\dot V\)O2 (ml · kg−1 · min−), and OBLA-WR, respectively. When AT-HR (X2) was added to the \(\dot V\)O2 (X1) as another predictor, the contribution of these variables to endurance performance increased appreciably to 84%. The resultant multiple regression equation was Y=−4.564 X1+2.68 IX2+90.6 (SEE=9.9 s). Consequently, it is suggested that variables related to an abrupt increase in blood lactate, together with several gas exchange responses, could explain endurance performance in a shorter distance to a greater extent than variables related to a rigid threshold of 4 mmol·l−1.

Aerobic capacity and fractional utilisation of aerobic capacity in elite and non-elite male and female marathon runners

Abstract: The physiology of marathon running has been extensively studied both in the laboratory and in the field, but these investigations have been confined to elite competitors. In the present study 28 competitors who took part in a marathon race (42.2 km) have been studied; 18 male subjects recorded times from 2 h 19 min 58 s to 4 h 53 min 23 s; 10 female subjects recorded times between 2 h 53 min 4 s and 5 h 16 min 1 s. Subjects visited the laboratory 2–3 weeks after the race and ran on a motor driven treadmill at a series of speeds and inclines; oxygen uptake \(\dot V\)O2 was measured during running at average marathon racing pace. Maximum oxygen uptake (\(\dot V\)O2 max) was measured during uphill running. For both males (r=0.88) and females (r=0.63), linear relationships were found to exist between marathon performance and aerobic capacity. Similarly, the fraction of \(\dot V\)O2 max which was sustained throughout the race was significantly correlated with performance for both male (r=0.74) and female (r=0.73) runners.

Recovery from short term intense exercise: Its relation to capillary supply and blood lactate concentration

Abstract: Muscle force recovery from short term intense exercise was examined in 16 physically active men. They performed 50 consecutive maximal voluntary knee extensions. Following a 40-s rest period five additional maximal contractions were executed. The decrease in torque during the 50 contractions and the peak torque during the five contractions relative to initial torque were used as indices for fatigue and recovery, respectively. Venous blood samples were collected repeatedly up to 8 min post exercise for subsequent lactate analyses. Muscle biopsies were obtained from m. vastus lateralis and analysed for fiber type composition, fiber area, and capillary density.

Relationship between isokinetic performance and ballistic movement.

Abstract: The present experiments were carried out to assess the relationship between the mechanical behaviour of the leg extensor muscles in 12 male athletes during activities of a ballistic type and torque production, during: (1) torque production during isokinetic contraction; (2) ballistic type activities (vertical jumps from static position = SJ, with counter-movement = CMJ and after a fall from different heights = DJ) and (3) a new anaerobic test (Bosco 1983a). This consisted of performing continuous jump work for a certain period of time (e.g., 60s). Both ballistic activities and anaerobic power tests demonstrated the highest relationship with peak torques when this was developed respectively at π and 4.2 rad·s−1. Peak torque was related to SJ (r=0.71, p<0.01); to CMJ (r=0.74, p<0.005); to best DJ (r=0.60, p<0.05), to 15 s anaerobic power (r=0.70, p<0.01) and 60 s anaerobic power (r=0.68, p<0.01). The power output during ballistic activities was much higher than the power measured during zero acceleration performances. The difference noted was explained in the light of the fact that, when jumping, three different extensor muscle groups in each leg contract with re-use during the concentric phase of elastic energy stored during the eccentric phase. The relationship between isokinetic contraction and ballistic motion is discussed in terms of fiber type recruitment and their velocity dependency.

Comparison of serum testosterone and androstenedione responses to weight lifting in men and women.

Abstract: To determine if a sex difference exists in the androgen response to heavy-resistance exercise, serum testosterone (T) and androstenedione (A) concentrations were measured in 20 men and 20 women before and during a 2-h period following 30 min of weight lifting. Hormone concentrations from venous blood samples were determined by radioimmunoassay. Prior to weight lifting, T for men (3.51±0.24 ng·ml−1) was approximately 10 times that for women (0.36±0.04 ng·ml−1), whereas A for women (1.26±0.07 ng·ml−1) was 43% higher than for men (0.88±0.07 ng·ml−1). Immediately following weight lifting, T was increased significantly (p<0.01) in men (0.76 ng·ml−1, 21.6%), but nonsignificantly in women (0.06 ng·ml−1, 16.7%). Resting T levels were restored within 30 min. Serum A levels decreased significantly (p<0.01) below pre-exercise levels at 2 h post-exercise for both men and women. It was concluded that men have a greater absolute T response to weight lifting than women, whereas the absolute A response to weight lifting is similar in men and women.

Effects of caffeine ingestion on metabolism and performance during graded exercise

Abstract: Seven trained men were studied during graded cycle ergometer exercise to assess the effects of caffeine ingestion on metabolism and performance. A single blind experimental procedure was followed with one trial being performed 60 min after the subject ingested caffeine (5 mg·kg−1) while the second trial required the subject to ingest a placebo with the treatment order being counterbalanced. Subjects began exercising at a work load of 30 W while the load was increased by an additional 30 W every 3 min until the subject could not maintain the desired pedal frequency. Venous blood samples were obtained at each work load and assayed for free fatty acids (FFA), glycerol, lactic acid, and caffeine. There was no significant difference (p>0.05) in time to exhaustion between the two experimental treatments. Resting measurements of FFA and glycerol showed that ingestion of caffeine brought about significant (p 0.05) between the two exercise tests. These data suggest that a small dose of caffeine does not change the rate of blood lactate accumulation nor does it enhance performance during graded cycle ergometer exercise.

Cardio-Respiratory Physical Training in Water and on Land,

Abstract: Fifteen unconditioned young men, who were similar in maximal aerobic power (VO2 max), were divided into three groups (n=5 each) and physically trained for one month on a cycle ergometer either on land (I) or immersed to the neck in water of either 32‡ C (II) or 20‡ C (III) to determine if physical training (PT) in water and air differ. PT consisted of one-hour daily exercise, 5 times/wk, with exercise intensity readjusted each week to maintain a constant training stimulus of ~ 75% VO2 max (determined on land). Throughout the training period, heart rates (fc) of III averaged 20 and 10 beats·min−1 less than I and II, respectively, despite working at the same VO2 and % VO2 max. Training elicited a 16% increase in VO2 max in I compared to increases of 13 and 15% for II and III, respectively. It was concluded that PT in water produces similar physiological adaptations as does training on land. In cold water, VO2 max is improved despite training with fc significantly lower than that on land.

Anaerobic threshold and lactate turnpoint.

Abstract: Venous lactate concentration and ventilatory responses to progressively increased work rates were studied in 16 men who performed an incremental exercise test to exhaustion on an electrically braked cycle ergometer. In this test the characteristic curvilinear increase in venous lactate concentrations was observed. In addition to the anaerobic threshold (AT), a second breakpoint was observed and named the lactate turnpoint (LTP). Eight of the 16 subjects performed a second incremental exercise test initiated during lactic acidosis. In this test the direction of change in venous lactate concentrations was different. The work rate at which lactate concentrations again increased, after a steady decline (previously described as the AT2), was similar to the work rate established for the LTP in the first test. In the second test removal of lactate was demonstrated at work rates exceeding the AT. Although the lactate response to the two tests was different the pattern of change was similar, with the two breakpoints occurring at the same work rates. Collectively these results lend a measure of support to the hypothesis of a positive relationship between the AT, LTP, and a pattern of recruitment of motor units with different enzyme profiles. Both the AT and LTP were predictable from the ventilatory response to incremental exercise.

Physiological properties of two antagonist human muscle groups.

Abstract: The physiological features of two antagonistic muscle groups, the dorsiflexors (DF) and plantarflexors (PF) of the ankle, have been compared in 46 healthy subjects (31 men and 15 women) aged 19–65 years. The DF muscles, of which tibialis anterior (TA) was studied most thoroughly, had relatively small twitches, with moderately fast contraction and relaxation phases, and had marked post-activation potentiation; they were susceptible to fatigue during isometric exercise. The PF muscles had comparatively large twitches, with slow contraction and relaxation phases, and poor post-activation potentiation; they were more resistant to fatigue. Women differed from men in having smaller TA twitches and slower PF twitches; PF twitches were also slower in older subjects. The marked differences in physiological properties between DF and PF muscles contrasted with relatively modest histochemical differences found by ourselves and others.

Energy metabolism of medium-chain triglycerides versus carbohydrates during exercise.

Abstract: Medium-chain triglycerides (MCT) are known to be rapidly digested and oxidized. Their potential value as a source of dietary energy during exercise was compared with that of maltodextrins (MD). Twelve subjects exercised for 1 h on a bicycle ergometer (60% VO2 max), 1 h after the test meal (1MJ). The metabolism of MCT was followed using 1-13C-octanoate (Oc) as tracer and U-13C-glucose (G) was added to the 13C-naturally enriched MD. After MCT ingestion no insulin peak was observed with some accumulation of ketone bodies (KB), blood levels not exceeding 1 mM. Total losses of KB during exercise in urine, sweat and as breath acetone were small (less than 0.2 mmol X h-1). Hence, the influence of KB loss and storage on gas exchange data was negligible. The partition of fat and carbohydrate utilization during exercise as obtained by indirect calorimetry was practically the same after the MCT and the CHO meals. Oxidation over the 2-h period was 30% of dose for Oc and 45% for G. Glycogen decrements in the Vastus lateralis muscle were equal. It appears that with normal carbohydrate stores, a single meal of MCT or CHO did not alter the contribution of carbohydrates during 1 h of high submaximal exercise. The moderate ketonemia after MCT, despite substantial oxidation of this fat, led to no difference in muscle glycogen sparing between the diets.

Variations in dietary-induced thermogenesis and body fatness with aerobic capacity

Abstract: Resting metabolic rate (RMR), dietary thermogenesis (DIT), aerobic capacity ( $$\dot V$$ O2 max), and percent body fat were measured in a group of sixteen women and ten men. DIT was significantly positively correlated with aerobic capacity (r=0.658). Percent body fat was significantly negatively correlated with $$\dot V$$ O2 max (r=−0.727). RMR was independent of $$\dot V$$ O2 max, or body fatness, but women had a significantly higher average RMR than men. Three men and three women participated in an endurance training program which significantly increased $$\dot V$$ O2 max. DIT was increased in proportion to the increase in aerobic capacity (r s=0.924), RMR was unchanged, and body fat decreased in males but not females. The controversy surrounding “luxuskonsumption” may stem in part from not taking into account individual differences in aerobic capacity when measuring DIT.

Some technical, physiological and anthropometrical aspects of speed skating.

Abstract: Five elite speed skaters and fourteen well trained skaters of a lower performance level performed three maximal tests: a 3,000 m race from which the skating position and the stroke frequency were derived, an oxygen consumption test both during skating and during a bicycle ergometer test. From all subjects anthropometric measures were taken. The elite group showed a $$\dot V$$ o2 during cycling of 64.4±3.5 ml·kg−1·min−1 and 59.4±3.7 ml·kg−1·min−1 during skating. The elite skaters showed: a shorter upper leg length with respect to total leg length, higher aerobic power during cycling, higher stroke frequency, smaller pre-extension knee angle coupled to higher work per stroke, higher “efficiency” during skating and higher external power during skating and during cycling when compared with the group of lower performance level. It is concluded that an important pre-requisite for speed skating appears to be the possibility to skate at a small pre-extension knee angle without an excessive claim to anaerobic metabolism.

Acute effects of cigarette smoking and inhalation of carbon monoxide during maximal exercise

Abstract: The acute effect of inhaling the smoke of three cigarettes was compared to the effect of inhalation of an amount of carbon monoxide (CO), giving the same CO-saturation of the arterial blood as smoking during rest and during maximal exercise on a Krogh cycle ergometer. Sixteen male subjects were tested in the morning (1) after about 8 h without smoking (control), (2) after inhalation of the smoke of three cigarettes (smoke), and (3) after CO-inhalation (CO). It was found that the average maximal rate of O2-uptake (\(\dot V_{O_2 } \) max) decreased during both smoke and CO by about 7%. Endurance time at \(\dot V_{O_2 } \) max decreased 20% during smoke but only 10% during CO. A significant decrease in maximal heart rate (HR), and an increase in HR at rest, was demonstrated only during smoke. The peak lactate concentration (HLa) following maximal exercise was significantly decreased after smoke. The results suggest that the decrease in \(\dot V_{O_2 } \) max during smoke is due to the CO-saturation of the blood, and hence to a decrease in the oxygen capacity of the blood, while the decrease in endurance time during smoke is a combined effect of the CO-saturation and an increased cost of breathing caused by the smoke particles. It is further suggested that nicotine, or possibly some other components of the smoke, have an enhancing effect on the heart at rest, while an inhibition is seen during maximal exercise. Finally it was found that the subjects who had a \(\dot V_{O_2 } \) max above the average for all subjects investigated were less susceptible to the effects of smoking than subjects with a \(\dot V_{O_2 } \) max below the average.

The effect of sleep deprivation on the plasma levels of hormones during prolonged physical strain and calorie deficiency.

Abstract: The effect of sleep on the serum levels of hormones during prolonged heavy physical strain and calorie deficiency were investigated in 19 young men participating in a 5 day ranger training course with a calorie consumption of 35,000–50,000 kJ·24 h−1, and a calorie intake of about 6,000 kJ·24 h−1. The subjects were divided into two groups: the stress group (8 cadets) were allowed no organized sleep during the course, whereas the sleep group (9 cadets) had 3 h sleep each night.

Diminished dietary thermogenesis in exercise-trained human subjects.

Abstract: The influence of exercise-training on dietary-induced thermogenesis (DIT) was investigated in humans. The resting metabolic rate was identical in trained and non-trained subjects, but the response to a meal containing 1,636 kcal (6.9 MJ) was markedly lower in trained subjects. Mean dorsal skin temperature, as measured by thermography, was not influenced by training. A significant correlation was observed between postprandial RQ and DIT, which indicates that the reduced energy expenditure noted in trained subjects is related to a greater lipid oxidation. This sparing effect of exercise-training on energy utilization in the form of carbohydrate, is interpreted as adaptive in the sense that energy is preserved for the purpose of producing work.

The time course of ammonia and lactate accumulation in blood during bicycle exercise

Abstract: The time course of venous blood ammonia and lactate formation has been investigated on 5 separate occasions in each of two subjects. Blood was sampled from a free flowing catheter for every 30 s during a ramp bicycle test to exhaustion. In each subject blood ammonia was rapidly elevated even at work rates as low as 40–50% of \(\dot VO_2\) max. On cessation of exercise blood concentrations fell rapidly. Lactate concentration in blood on the other hand was more slowly elevated during the test and continued to rise in the usual fashion after the completion of the work. It is suggested that ammonia may be a primary toxin during exhaustive exercise inducing changes, which ultimately become incapacitating, in essential metabolic functions.

Effect of isometric and isokinetic muscle training on static strength and dynamic power.

Abstract: This study investigated whether isokinetic strength training might induce changes in static and dynamic power already achieved as a result of isometric strength training. The subjects were twelve males. The isometric strength and dynamic power of elbow flexors were tested by means of an electric dynamometer and fly-wheel every two weeks. During the first 8 weeks all subjects trained the elbow flexors isometrically at four different positions of elbow joints. This training produced 27–36% gains in isometric strength and 34–46% in power. Thereafter the subjects were divided into two groups: the FG group who trained isokinetically at a fast velocity of 157‡·s−1, and the SG group at slow velocity of 73‡·s−1. After 6 weeks of training, the FG group produced a significant gain in power with light equivalent masses and the SG group did so with heavy equivalent masses. Neither group showed change in isometric strength.

Greater serum GH response to arm than to leg exercise performed at equivalent oxygen uptake.

Abstract: The aim of this study was to provide information concerning the mechanism of exercise-induced stimulation of growth hormone (GH) release in human subjects. For this reason serum GH as well as some hemodynamic variables and blood concentrations of noradrenaline (NA), insulin (IRI), lactate (LA), glucose (BG), and free fatty acids (FFA) were determined in seven healthy male subjects exercising on a bicycle ergometer with arms or legs and running on a treadmill at equivalent oxygen consumption levels. Significantly greater increases in serum GH concentration accompanied arm exercises than those observed during the leg exercises. This was accompanied by greater increases in heart rate, blood pressure, and plasma NA and blood lactate concentrations. Serum IRI decreased during both leg exercises and did not change during the arm exercise. There were no differences in BG and plasma FFA concentrations between the three types of exercise.