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Biomedical subjects

P Rahkila

Publications and source records attributed to P Rahkila.

At least 37 records · Page 2Linked to original sources
PubMed1990

Mechanical work and efficiency in treadmill running at aerobic and anaerobic thresholds.

Mechanical work, mechanical power, energy consumption and mechanical efficiency were studied in constant-speed treadmill running of 5 min at seven different exercises around aerobic (AerT) and anaerobic (AnT) thresholds. The true efficiency of concentric (positive) mechanical work and gross efficiency of the whole body in seven male subjects were calculated. The total mechanical work was calculated from film through the translational, potential and rotational energy states as the sum of the changes of all the mechanical energy states in all body segments allowing energy transfer between segments and from energy state to state. The total energy consumption was measured by combining aerobic and anaerobic energy production in resting and working conditions. When the speed of the treadmill was increased from the velocity of 10 km h-1 (2.8 m s-1) to 22 km h-1 (6.1 m s-1), the concentric mechanical work per one step increased from 129 +/- 45 J to 228 +/- 82 J (P less than 0.01). Oxygen consumption increased from 2.22 +/- 0.27 1 min-1 to 4.47 +/- 0.24 1 min-1. The amount of blood lactate increased from 0.94 +/- 0.53 mmol l-1 at the lowest speed to 9.90 +/- 2.89 mmol l-1 at the highest speed (P less than 0.001). The true efficiency of concentric work decreased from 74 +/- 14% to 56 +/- 8% (P less than 0.05). At the speed of the AerT, the economy of running, the vertical rise of different body segments and mechanical efficiency of positive work were high. The highest gross efficiency was found at the running speed between the AerT and AnT.

Adolescent↗
PubMed1990

Serum carbonic anhydrase III and myoglobin concentrations in acute myocardial infarction.

Serum concentrations of myoglobin (S-Myo) and carbonic anhydrase III (S-CA III; EC 4.2.1.1), a skeletal muscle-specific protein, were measured by RIA in 26 patients with acute myocardial infarction, 14 patients with neuromuscular diseases, and six healthy subjects before and after physical exercise. S-Myo was increased in infarct patients, whereas S-CA III was not altered. In patients with neuromuscular diseases and in healthy subjects after physical exercise, both S-Myo and S-CA III were significantly increased. S-CA III and S-Myo also showed identical peak times, 2 h postexercise. The S-Myo/S-CA III ratio was always higher in infarct patients than in the other groups. Thus, the combination of S-CA III and S-Myo determinations is useful to differentiate whether serum myoglobin is originating from myocardium or from skeletal muscle.

Adult↗
PubMed1989

Serum carbonic anhydrase III, an enzyme of type I muscle fibres, and the intensity of physical exercise.

The effects of 30 min running with stepwise increasing intensity (exhaustive, energy demand approx. 50----100% of VO2max), 60 s supramaximal running (anaerobic, greater than or equal to 125% of VO2max) and 40-60 min low-intensity running (aerobic, 40-60% of VO2max) on serum concentration of muscle-derived proteins were studied in 5 male and 5 female elite orienteerers. S-Carbonic anhydrase III (S-CA III) was used as a marker of protein leakage from type I (slow oxidative) muscle fibres and S-myoglobin (S-Mb) as a non-selective (type I + II) muscular marker. The fractional increase in S-CA III (delta S-Ca III) was 0.37 +/- 0.09 (mean +/- SEM, p less than 0.001), 0.10 +/- 0.05 (N. S.) and 0.46 +/- 0.09 (p less than 0.001) 1 h after exhaustive, anaerobic and aerobic exercise, respectively. The corresponding values for delta S-Mb were 1.45 +/- 0.36 (p less than 0.001), 0.39 +/- 0.13 (p less than 0.01) and 0.67 +/- 0.18 (p less than 0.001). The value for the delta S-CA III/delta S-Mb ratio was 0.68 +/- 0.03 after the aerobic exercise, but only 0.25-0.26 (p vs. aerobic exercise less than 0.001) after the two high-intensity forms of exercise. Since type I fibres of skeletal muscle are known to be responsible for power production during low-intensity exercise, whereas fibres of both type I and type II are active at higher intensities, the delta S-CA III/delta S-Mb ratio may depend on the recruitment profile of type I vs. type I + II fibres.

Adult↗
PubMed1988

Beta-endorphin and corticotropin release is dependent on a threshold intensity of running exercise in male endurance athletes.

Relationship between the intensity of running exercise on a treadmill and the changes in the concentrations of beta-endorphin + beta-lipotropin (beta-E + beta-LPH) and adrenocorticotropic hormone (ACTH) in plasma were studied in 10 experienced male endurance athletes. At random order, the subjects run on a treadmill six exercises which required on an average (mean +/- S.E.) 50 +/- 0.8%, 58 +/- 0.8%, 69 +/- 1.1%, 80 +/- 0.7%, 92 +/- 1.0% and 98 +/- 0.5% of their maximal oxygen consumption. Plasma levels of beta-E + beta-LPH and ACTH did not show any significant changes during the 50-80%-tests. During the 92% test, the mean levels (+/- S.E.) of beta-E + beta-LPH and ACTH increased significantly (p less than 0.001), from 3.0 +/- 0.4 to 8.0 +/- 1.2 pmol/l and from 3.1 +/- 0.5 to 8.9 +/- 1.3 pmol/l, respectively, and during the 98% test, from 3.7 +/- 0.6 pmol/l to 20.4 +/- 1.5 pmol/l, and from 3.6 +/- 0.6 to 21.8 +/- 1.5 pmol/l, respectively. Increases in the plasma levels of beta-E + beta-LPH and ACTH were always accompanied by an increase in the blood lactate level. We conclude that intensive running with an anaerobic response causes an increase in the concentrations of beta-endorphin and ACTH in plasma in endurance athletes, whereas slight aerobic exercise did not elicit any response.

Adrenocorticotropic Hormone↗
PubMed1987

Mechanical jumping power in young athletes.

Mechanical jumping power was determined for 286 young male athletes representing six sports events and ranging in calendar and skeletal ages from 8.8 to 17.1 and from 7.8 to 18.1 years, respectively. The subjects performed successive maximal vertical jumps on a contact mat for 30 s. The number of jumps and their cumulative flight time after 15 and 30 s were used for calculations of mechanical power. The jumping performances of the young athletes were found to be reproducible from the age of 10-12 years in respect to the angular displacement of the knee and duration of contact. Absolute mechanical power, as well as power related to body weight, increased with calendar and skeletal ages. Of the anthropometric characteristics, the circumference of the thigh and body weight showed the highest correlation with mechanical power; subjects with the greatest thigh circumference and body weight having the lowest mechanical power. The subjects were divided into 'power' (track and field, gymnastics) and 'endurance' (skiing, orienteering) groups. The former reached higher mechanical power values than the latter. Mechanical power for the second 15-s jumping period was on average 4.7% lower than for the first. The events did not differ from each other in respect of the decrease in power.

Adolescent↗
PubMed1987

Mechanical work and efficiency in ergometer bicycling at aerobic and anaerobic thresholds.

Internal and external mechanical work, energy consumption and mechanical efficiency were studied in constant-load ergometer bicycling at five different power outputs below, equal to, and above the aerobic (AerT) and anaerobic (AnT) thresholds. The gross, net and true efficiencies of the whole body in five male subjects were calculated. The work against the external load was defined as the external mechanical work. The internal mechanical work was calculated as the sum of the increments of kinetic and potential energy in all body segments by using methods of film analysis. Total energy consumption was measured by combining aerobic and anaerobic energy production. When the power output of the bicycle ergometer was increased from 146 +/- 15 to 283 +/- 17 W, oxygen consumption increased from 2.20 +/- 0.98 to 4.22 +/- 0.20 l min-1 (P less than 0.001), while the oxygen consumption at rest was 0.30 +/- 0.03 l min-1. The concentration of blood lactate increased from 2.2 +/- 0.4 at the lowest work load to 8.6 +/- 1.2 mmol l-1 at the highest work load (P less than 0.001). The amount of external work done per revolution increased from 139 +/- 20 to 277 +/- 29 J (P less than 0.001), while the amount of internal work per revolution remained almost constant (56 +/- 12 J). The gross efficiency in the present study was 17-20%, net efficiency 18-22% and true efficiency 21-30%, respectively. The highest gross and net efficiencies were reached at the AerT. The lowest efficiencies were obtained at highest work load.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Effect of androgenic and anabolic steroids on the sebaceous gland in power athletes.

The effect of androgenic and anabolic steroids on sebaceous gland activity and the composition of sebum was studied in power athletes. The subject self-administered large doses of androgenic and anabolic hormones during a 12-week-period of strength training. After 4 weeks of administration of hormones the sebum excretion rate increased significantly (p = 0.002) and it remained high throughout the period of exogenous steroid use. The amounts of cholesterol were significantly increased during that period. There were no differences in the amounts of the following lipid groups; free fatty acids, squalen, triglycerides, wax esters, diglycerides and paraffins. It was concluded that large doses of androgenic and anabolic steroids lead to an increase in sebum output in healthy young adult males.

Adult↗
PubMed1987

Response of plasma endorphins to running exercises in male and female endurance athletes.

We studied the responses of plasma concentrations of beta-endorphin, beta-lipotropin, and corticotropin to an exhaustive graded treadmill exercise, to an anaerobic treadmill exercise, and to a sub-maximal outdoor running exercise in 5 male and in 5 female endurance athletes. During the graded treadmill exercise, the mean plasma level (+/- SE) of beta-endorphin in men rose from 1.2 +/- 0.1 to 8.1 +/- 0.7 pmol.l-1, beta-lipotropin rose from 1.6 +/- 0.5 to 7.4 +/- 1.4 pmol.l-1, and corticotropin rose from 4.9 +/- 1.0 to 31 +/- 3.3 pmol.l-1. In women, the mean level of beta-endorphin rose from 1.2 +/- 0.2 to 8.2 +/- 1.8 pmol.l-1, beta-lipotropin rose from 1.4 +/- 0.1 to 8.1 +/- 2.0 pmol.l-1, and corticotropin rose from 3.3 +/- 0.4 to 28 +/- 7.9 pmol.l-1. Concentrations of endorphins and corticotropin increased significantly also during the anaerobic exercise test. In response to sub-maximal running exercise, no significant change was found. These results showed a relationship between the intensity of exercise and the secretion of pro-opiomelanocortin-related peptides, and there were no differences between the groups of trained men and women.

Adrenocorticotropic Hormone↗
PubMed1986

Muscle metabolism, blood lactate and oxygen uptake in steady state exercise at aerobic and anaerobic thresholds.

Muscle metabolites and blood lactate concentration were studied in five male subjects during five constant-load cycling exercises. The power outputs were below, equal to and above aerobic (AerT) and anaerobic (AnT) threshold as determined during an incremental leg cycling test. At AerT, muscle lactate had increased significantly (p less than 0.05) from the rest value of 2.31 to 5.56 mmol X kg-1 wet wt. This was accompanied by a significant reduction in CP by 28% (p less than 0.05), whereas only a minor change (9%) was observed for ATP. At AnT muscle lactate had further increased and CP decreased although not significantly as compared with values at AerT. At the highest power outputs (greater than AnT) muscle lactate had increased (p less than 0.01) and CP decreased (p less than 0.01) significantly from the values observed at AnT. Furthermore, a significant reduction (p less than 0.05) in ATP over resting values was recorded. Blood lactate decreased significantly (p less than 0.01) during the last half of the lowest 5 min exercise, remained unchanged at AerT and increased significantly (p less than 0.05-0.01) at power outputs greater than or equal to AnT. It is concluded that anaerobic muscle metabolism is increased above resting values at AerT: at low power outputs (less than or equal to AerT) this could be related to the transient oxygen deficit during the onset of exercise or the increase in power output. At high power outputs (greater than AnT) anaerobic energy production is accelerated and it is suggested that AnT represents the upper limit of power output where lactate production and removal may attain equilibrium during constant load exercise.

Adult↗
PubMed1986

Testicular responsiveness to human chorionic gonadotrophin during transient hypogonadotrophic hypogonadism induced by androgenic/anabolic steroids in power athletes.

Serum concentrations of testosterone, 17-hydroxyprogesterone, estradiol and several other unconjugated and sulphated steroids were analyzed before and after a single dose of hCG in 6 power athletes, who had used high doses of testosterone and anabolic steroids for 3 months. The study was carried out 3 weeks after cessation of drug use, but the study subjects were still characterized by hypogonadotrophic hypogonadism. The mean concentrations of serum LH and FSH were 2.6 +/- 0.3 and 1.1 +/- 0.03 mIU/ml (mean +/- SEM), respectively, and the concentrations of several precursors and metabolites of testosterone were lower than those before drug use. In contrast, circulating concentrations of steroid sulphates were not decreased, with the exception of dehydroepiandrosterone sulphate. After hCG injection serum testosterone and 5 alpha-dihydrotestosterone concentrations increased significantly, whereas no increases in estradiol and 17-hydroxyprogesterone concentrations were observed. These results demonstrate that during transient hypogonadotrophism in adult men, the testicular responsiveness to a single injection of hCG is similar to that in prepubertal boys without any sign of steroidogenic lesion at the 17,20-desmolase step. Therefore, the appearance of the possibly estradiol-mediated inhibition at the level of C21-steroid side-chain splitting in testosterone biosynthesis seems to be dependent on priming by gonadotrophins.

Adult↗
PubMed1985

Serum lipids in power athletes self-administering testosterone and anabolic steroids.

The purpose of the present investigation was to study the effects of testosterone and anabolic steroids on serum lipids in power athletes. Altogether 11 national top-level adult athletes completed the study. Five of them volunteered for the study group and the rest for controls. The follow-up consisted of 9 months of a strength training period. During the first 6 months, the subjects in the study group self-administered androgenic steroids on an average of 57 +/- 24.9 mg/day. The most interesting observation was the extremely low high-density lipoprotein (HDL) and HDL2 cholesterol concentrations of the androgen users. After 8 weeks of training, the study group had significantly (P less than 0.05) lower HDL cholesterol concentrations than the control group (0.53 +/- 0.11 and 1.14 +/- 0.19 mmol/l, respectively). This difference remained significant from 8 to 32 weeks of training. No systematic changes were observed in the control group. The HDL2 cholesterol concentration decreased by about 80% (P less than 0.01) and HDL3 cholesterol by about 55% (P less than 0.01) from the onset values in the study group. A substantial decrease in HDL cholesterol to total cholesterol and in HDL2 cholesterol to HDL3 cholesterol ratios were also noticed under the influence of exogenous androgens. The results of this study suggest that the sustained use of testosterone and anabolic steroids have a marked unfavorable effect on the pattern of HDL cholesterol in the serum of male power athletes.

Adult↗
PubMed1985

Electromyographic activity related to aerobic and anaerobic threshold in ergometer bicycling.

Electromyographic activity (EMG) of the knee extensor musculature (m. vastus lateralis, m. vastus medialis, m. rectus femoris), triceps surae (m. gastrocnemius, m. soleus) and m. tibialis anterior was studied in ergometer bicycling at five different power outputs around aerobic (AerT) and anaerobic (AnT) thresholds. EMGs were sampled with surface electrodes for ten revolutions at the beginning, in the middle and at the end of each work load and integrated (IEMG) separately for each of the muscles and for the descending (work) and ascending (rest) phase of the revolution. The mean power frequency (MPF) of the power spectral density function for the descending periods was also calculated. The first work load was 50% of the maximal load, the second at the level of AerT, the third at the AnT, the fourth between the AnT and the maximal load and the fifth load was maximal. The AerT and AnT were determined using blood lactate, ventilation volume and oxygen consumption. Five males from 21 to 38 years of age volunteered as subjects. When the IEMGs of the knee extensor and triceps surae musculature were related to the work load a nonlinearity was found at the aerobic threshold while no further change in the linearity was found at the AnT. The non-linear increase of the IEMG at the AerT was found both for the working (descending) and resting (ascending) phases of the cycling. In the MPF no difference below and above the AnT was found. It was thought that the integral of EMG activity could serve as an indicator of the aerobic threshold of an individual muscle.

Adult↗
PubMed1984

Metabolic changes induced by combined prolonged exercise and low-calorie intake in man.

Thirteen middle-aged women and 10 men walked 344 km during 7 days. The daily walking distances were 57, 53, 67, 53, 41, 36, and 37 km at an average speed of 3.5 km X h-1. During the hike the subjects drank water, mineral drinks, and juices ad libitum. Except for some natural products, no food intake was allowed. During the hike the body weight and serum protein concentration of the subjects decreased by about 7%, on average. Serum triglyceride and total cholesterol decreased drastically, about 30-40% during the hike, but HDL-cholesterol showed a tendency to increase, giving a 40% increment in HDL/total cholesterol ratio. Serum free fatty acids rose 1.5-2 times above the starting level. Serum glucose and evening insulin levels decreased significantly during the hike. Serum cortisol in evening samples after the daily walking and plasma norepinephrine concentrations were significantly increased, reflecting the immediate daily response to the combined fasting and walking. Serum testosterone levels decreased in men but not in women, indicating the involvement of the LH-testis pathway in the decrease obtained. Serum ASAT activity rose to about three times the starting level during the hike, whereas gamma-GT activity gradually decreased. These marked metabolic changes caused by combined fasting and several days exercise were in many respects (as in cholesterol, HDL/total cholesterol ratio or testosterone levels) more pronounced than those earlier reported to be caused by exercise or fasting alone.

Adult↗
PubMed1984

Reduced high-density lipoprotein-cholesterol in power athletes: use of male sex hormone derivates, an atherogenic factor.

The effect of androgenic steroids on plasma lipids was studied in seven power athletes who self-administered androgenic steroids on the average 45 mg/day during an 8-week strength training period. At the beginning of the study, no significant differences were noticed in HDL-cholesterol levels between the steroid users and the controls. After 8 weeks of strength training, the androgen users had reduced the HDL-cholesterol by 54% (from 1.47 to 0.67 mmol/l). The difference when compared to controls was highly significant (P less than 0.001). It was concluded that the use of androgenic steroids combined with strength training decreases serum HDL-cholesterol and thus may cause a higher risk for coronary heart disease.

Adult↗
PubMed1984

Functional capacity of men born in 1906-10, 1926-30 and 1946-50. A basic report.

This interdisciplinary study aims at describing the functional capacity of men belonging to different generation cohorts. The development of methods for the assessment of functional capacity is also the purpose of the study. Functional capacity is defined as a hierarchy comprising physical, mental and social areas into which individuals can be placed depending on the levels of the assessed functions. The study also aims at analyzing environmental and individual factors which are assumed to cause variation in the levels of functions. The purpose of this first report is to describe the framework of the study, the methods and main results concerning differences between cohorts and occupational groups. The sampling frame consisted of the population register of Jyväskylä town in January 1981. The basic populations were men in three age groups, born in 1946-50, 1926-30 and 1906-10. From each age group a systematic random sample of 250 men was made. Persons who had moved or died by the end of August 1981 or were living in institutions (6 men) were removed from the samples. The sample sizes were further randomly reduced so that the final samples consisted of 183, 188 and 176 men. At the time of the study the ages of the cohorts were 31-35, 51-55 and 71-75. The study included postal questionnaires, interviews and laboratory examinations. The basic questionnaire dealt with the background information, living conditions, life history, occupational history, social contracts and social participation, close human relations, use of time, health status and living habits. The second postal questionnaire dealing with psychic capacity included the following main items: life changes, self-realisation, personal trait anxiety, social fears, coping, self-respect, and the purpose of life. The basic questionnaire was checked in an interview when the subjects came for the laboratory examinations. The entrance interview also included questions about the most important events of previous 24 hours. In addition the subjects filled in a questionnaire on situational anxiety. The laboratory examinations included the following tests: cognitive capacity (4 tests), audiometry, speech understanding, visual tests, vibration threshold, posture control, reaction and movement time, tapping rate, leg extension velocity, anthropometric measurements, skin measurements, bone mineral density, physiotherapist's examination, physician's examination, blood analyses, isometric strength of muscles (5 muscles), anaerobic power, aerobic power and anaerobic threshold.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1982

Neuromuscular function and mechanical efficiency of human leg extensor muscles during jumping exercises.

The influence of prestretch amplitude on the mechanical efficiency was examined with 5 subjects, who performed 5 different series of vertical jumps, each of which differed with respect to the mechanics of the knee joint action during the prestretch (eccentric) phase of the contact on the floor. Electromyographic activity was recorded from the major extensor muscles during the entire work period of 1 min per series. In addition, expired air was collected during the test and recovery for determination of energy expenditure. Mechanical work was calculated from the vertical displacement of the body during the jumps. The results indicated that high net efficiency of 38.7% was observed in condition where amplitude of knee bending in eccentric phase was small. In large range motion the corresponding net efficiency was 30.1%. In jumps where no prestretching of extensor muscles occurred the net efficiency was 19.7%. The high efficiency of small amplitude jumps was characterized by low myoelectrical activity of the leg extensor muscles during the positive (concentric) work phase. In addition, the small amplitude jumps had shorter transition time in the stretch-shortening cycle, high average eccentric force and high stretching speed. Therefore the results suggest that the restitution of elastic energy, which was also related to the length change and stiffness of the muscles during stretch, plays an important role in regulating the mechanical efficiency of work.

Adult↗
PubMed1980

Lipid metabolism during exercise. II. Respiratory exchange ratio and muscle glycogen content during 4 h bicycle ergometry in two groups of healthy men.

Seven physically fit (well-trained, maximal oxygen uptake 69.6 +/- 4.4 ml x kg-1 min-1) and eight less fit (moderately trained, maximal oxygen uptake 56.1 +/- 5.7 ml x kg-1 x min-1) healthy male subjects were exercised for 4 h by bicycle ergometry against a pedalling resistance calculated to cause oxygen consumption corresponding to approximately 30% of each individual's maximal oxygen uptake value. Respiratory exchange ratio was estimated at 1 h and blood glucose and lactate concentrations and muscle glycogen content at 2 h intervals. Muscle glycogen content decreased markedly during the first 2 h of exercise in the well-trained group but was similar after 4 h exercise in both groups. No major differences were observed between the two subject groups in blood variable concentrations. Calculations based on respiratory exchange ratio showed that the proportion of carbohydrates utilized in the total energy consumption was 14% in the physically fit group and 25% in the less fit group, thus supporting previous observations that more energy is derived by fat oxidation in well-trained than in less-trained individuals during submaximal work at relatively similar oxygen consumption levels.

Blood Glucose↗