Biomedical subjects

H Rusko

Publications and source records attributed to H Rusko.

At least 55 records · Page 3Linked to original sources

PubMed1989

A comparative study of blood lactate tests in swimming.

Three different modes of lactate tests were studied. Eleven male competitive swimmers performed the tests (n.100 m, n.300 m, 2.100m + 2.400 m) within 5 days. Swimming velocity (V) vs blood lactate (BLa) and V vs heart rate (HR) curves were averaged. In V vs BLa comparisons, the BLa values of 4 mmol.l-1 in 2.400 m, 3 mmol.l-1 in n.300 m, and 2 mmol.l-1 in n.100 m modes were found to correspond to the same V. Although the resting BLa values were similar before the testing occasions, the initial BLa value in very easy swimming was lower in the n.300 m than in the n.100 m mode. The elimination of lactate most probably caused this difference. The highest BLa value was measured in the n.100 m (14.9 mmol.l-1) and 2.100 m (13.6 mmol.l-1) exercise modes demonstrating a higher rate of anaerobic energy production than in the n.300 m or 2.400 m test modes. In HR vs V comparison, the n.300 m and 2.400 m modes demonstrated similar HR values in relation to V. To measure the whole intensity area, a combination of tests should be applied by performing an incremental set with several steady-state loadings (aerobic) and one or two 100 m swims (anaerobic) in one test session.

Adolescent↗

PubMed1988

Comparison of two methods for aerobic threshold determination.

A new method of aerobic threshold (AerT) determination, as a minimum of so-called lactate equivalent (Berg et al. 1980; Lehmann et al. 1983), was compared with the generally used method (AerT1) presented first by Wasserman et al. (1973). The comparison was made with data from 32 subjects in repeated maximal exercise tests on a bicycle ergometer. The AerT as a minimum of lactate equivalent was determined using both a computerized method for curve fitting (AerT3) and visual inspection (AerT2). AerT2 and AerT3 showed similarity: the regression coefficient was 0.88 and 0.95 and the correlation coefficient was 0.84 and 0.88 in the first and in the second tests, respectively. AerT1 and AerT2 showed similar mean estimated values, but AerT3 showed slightly higher mean values than AerT1 (p less than 0.05 and p less than 0.01) or AerT2 (p less than 0.01). The regression coefficients between AerT1 and AerT2 or AerT3 (0.60-0.71) showed different slopes from the identity (p less than 0.001). The corresponding correlation coefficients were 0.88 and 0.89 with AerT2, and 0.75 and 0.79 with AerT3 respectively in the first and second tests. However, in two thirds of all determinations the difference between these two estimation methods (AerT1 and AerT2) was less than or equal to 0.10 l O2.min-1. In conclusion, AerT as a minimum of lactate equivalent differed slightly from AerT determined using the traditional method. However, its determination criterion is unambiguous and allows objective computerized curve fitting. The physiological correlates of this new AerT index should be studied carefully before final evaluation of its usefulness in applications can be made.

Adult↗

PubMed1988

Muscle metabolic profile and oxygen transport capacity as determinants of aerobic and anaerobic thresholds.

Aerobic and anaerobic thresholds determined by different methods in repeated exercise tests were correlated with cardiorespiratory variables and variables of muscle metabolic profile in 33 men aged 20-50 years. Aerobic threshold was determined from blood lactate, ventilation, and respiratory gas exchange by two methods (AerT1 and AerT2) and anaerobic threshold from venous lactate (AnTLa), from ventilation and gas exchange (AnTr) and by using the criterion of 4 mmol.1(-1) of venous lactate (AnT4mmol). In addition to ordinary correlative analyses, applications of LISREL models were used. The 8 explanatory variables chosen for the regression analyses were height, relative heart volume, relative diffusing capacity of the lung, muscle fiber composition, citrate synthase (CS) and succinate dehydrogenase activities, the lactate dehydrogenase--CS ratio, and age. They explained 58% of the variation in AerT1, 73.5% that of AerT2, 71% that of AnTr, 74.5% that of AnTLa, and 67.5% that of AnT4mmol.AerT and AnT alone explained 77% of the variation in each other. Both AerT and AnT were determined mainly by a muscle metabolic profile, with the CS activity of vastus lateralis as the strongest determinant. The factor 'submaximal endurance' which was measured with AerT and AnT seemed to be slightly more closely connected to 'muscle metabolic profile' than was 'maximal aerobic power' (= VO2max), but both also correlated strongly with each other (r = 0.92).

Adult↗

PubMed1987

Metabolic response of endurance athletes to training with added load.

Endurance athletes were divided into experimental (n = 12) and control (n = 12) groups to investigate the effects of extra-load training on energy metabolism during exercise. A vest weighing 9%-10% body weight was worn every day from morning to evening for 4 weeks including every (n = 6) or every other (n = 6) training session. After 4 weeks the control group had a lower blood lactate concentration during submaximal running, whereas the experimental group had significantly higher blood lactate and oxygen uptake (p less than 0.01--p less than 0.05), and a lower 2 mmol lactate threshold (p less than 0.05) and an increased blood lactate concentration after a short running test to exhaustion (p less than 0.05). Those experimental subjects (n = 6) who used the added load during every training session had a lower 2 mmol lactate threshold, improved running time to exhaustion, improved vertical velocity when running up stairs and an increased VO2 during submaximal running after the added load increased anaerobic metabolism in the leg muscle during submaximal and maximal exercise. An increased recruitment and adaptation of the fast twitch muscle fibres is suggested as the principal explanation for the observed changes.

Adult↗

PubMed1987

Breakdown of high-energy phosphate compounds and lactate accumulation during short supramaximal exercise.

Muscle ATP, creatine phosphate and lactate, and blood pH and lactate were measured in 7 male sprinters before and after running 40, 60, 80 and 100 m at maximal speed. The sprinters were divided into two groups, group 1 being sprinters who achieved a higher maximal speed (10.07 +/- 0.13 m X s-1) than group 2 (9.75 +/- 0.10 m X s-1), and who also maintained the speed for a longer time. The breakdown of high-energy phosphate stores was significantly greater for group 1 than for group 2 for all distances other than 100 m; the breakdown of creatine phosphate for group 1 was almost the same for 40 m as for 100 m. Muscle and blood lactate began to accumulate during the 40 m exercise. The accumulation of blood lactate was linear (0.55 +/- 0.02 mmol X s-1 X l-1) for all distances, and there were no differences between the groups. With 100 m sprints the end-levels of blood and muscle lactate were not high enough and the change in blood pH was not great enough for one to accept that lactate accumulation is responsible for the decrease in running speed over this distance. We concluded that in short-term maximal exercise, performance depends on the capacity for using high-energy phosphates at the beginning of the exercise, and the decrease in running speed begins when the high-energy phosphate stores are depleted and most of the energy must then be produced by glycolysis.

Adenosine Triphosphate↗

PubMed1987

Neuromuscular and anaerobic performance of sprinters at maximal and supramaximal speed.

Neuromuscular and anaerobic performance was investigated in nine male sprinters who were running at maximal and supramaximal speeds. Supramaximal running was performed by a towing system. A rubber rope pulled by an electronic motor towed the runner, and the angle of draught ranged from 10 degrees to 17 degrees upward from the horizontal. All runs were filmed at 100 frames X s-1, and ground reaction forces were measured with a long force platform system. EMGs were recorded telemetrically with surface electrodes from five leg muscles. Blood lactate and oxygen debt were measured during recovery. The results indicated that in supramaximal running the increases in velocity (4.3%-4.6%) were associated with increase in stride length (P less than 0.01). Comparison of the ground reaction forces showed that in the impact phase maximal force, average force, work, and power were significantly (P less than 0.01-0.001) greater in a horizontal direction and maximal and average forces were greater (P less than 0.05-0.01) in a vertical direction compared with a preceding maximal run. There were no significant differences in EMG activity of any studied muscle between the various runs. Peak blood lactate was 27.7% (P less than 0.001) and oxygen debt 30.3% (P less than 0.01) higher after maximal than supramaximal runs. It is concluded that supramaximal running with towing horizontally and vertically simultaneously causes increases in stride length and changes are associated with a smaller energy expenditure despite the high intensity of the performance.

Adult↗

PubMed1987

The effect of training on aerobic power characteristics of young cross-country skiers.

The influences of growth, training and various training methods were investigated by analysing long-term training effects in young cross-country and biathlon skiers (n = 129). Some athletes (n = 49) were studied six times in three years and some at least once a year during a four year period (n = 48). During three summer training periods skiers emphasized either intensive training or distance training or continued to train normally. The results indicated that maximal oxygen uptake (VO2 max) and heart volume increased between 15 and 20 years of age and the most significant changes in heart volume were observed between 16 and 18 years of age. International level skiers were able to increase their VO2 max and heart volume even after 20 years of age. Anaerobic threshold (AT, ml kg-1 min-1) increased like VO2 max but when expressed as a percentage of VO2 max, the AT was similar in every age group over 16 years of age. Intensive training at the intensity of anaerobic threshold or higher was observed to be most effective in producing improvements in VO2 max. Low-intensity distance training was more effective in producing improvements in anaerobic threshold.

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↗

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

Aerobic and anaerobic thresholds determined from venous lactate or from ventilation and gas exchange in relation to muscle fiber composition.

The aerobic and anaerobic thresholds determined from venous lactate (AerTLa and AnTLa) or from ventilation and gas exchange (AerTr and AnTr) in relation to muscle fiber composition were compared. Twelve subjects were studied in double exercise tests carried out until voluntary exhaustion. They were divided into two groups according to their muscle fiber type in the vastus lateralis muscle: ST group with a majority of slow-twitch fibers (ST% = 66.0% +/- 7.3%) and FT group with a majority of fast-twitch fibers (ST% = 27.7% +/- 8.4%). A 2-min incremental exercise test protocol on a bicycle was used. There were no significant differences between the ST and FT groups in the VO2max or in the Lamax. Neither the AerT nor the AnT related to the VO2max (%) differed between the ST and FT groups. In the FT group the AnTLa occurred 0.70 min in the first test and 1.06 min in the second test earlier than the AnTr, whereas in the ST group the AnTLa occurred at the same time or 0.44 min later, respectively, than the AnTr (P less than 0.05). Expressed as VO2 the differences between thresholds were not so distinct. The results demonstrated that the mutual relation between the AnTLa and AnTr seemed to be dependent on the fiber type majority in exercising muscles (vastus lateralis) among untrained men.

Adult↗

PubMed1986

The effect of fatigue on store and re-use of elastic energy in slow and fast types of human skeletal muscle.

Stretch-shortening exercises are characterized by enhancement of performance when compared to the work output performed in shortening conditions. There is evidence that fast subjects are unable to re-use great amounts of elastic energy during stretch-shortening cycles performed with slow stretching speed and large stretching length. In the present study, 14 subjects possessing different fibre types in m. vastus lateralis performed vertical jumps with and without preliminary countermovement and with large angular displacement and slow stretching speed The jumping tests were executed before and immediately after fatigue induced by short intense exercises (60 s of continuous rebound jumping). The results indicated that the percentage of re-use of elastic energy was more pronounced in slow subjects compared to fast ones during the test performed before fatigue (28.3% vs. 22.8%). In contrast fast subjects demonstrated a greater percentage re-use of elastic energy than slow ones after fatigue (32% vs. 22.5%). Similarly, the negative relationship observed before fatigue, between the percentage of re-use of elastic energy and percentage of fast twitch fibres (r = 0.50, n = 14, P less than 0.05), was reversed after fatigue (r = 0.55, n = 14, P less than 0.05). The results can be interpreted through differences in sarcomere cross-bridges life-times between fast and slow twitch muscle fibres. The slow twitch-type muscle fibre may be able to retain the cross-bridge attachment for a longer period of time during no fatigued conditions, and therefore it may utilize elastic energy better in slow type ballistic motion. On the other hand, fast twitch type muscle fibres are more affected by fatigue, which might have induced a remarkable decrease of the cross-bridge attachment detachment cycle. Decrease of the cross-bridge rate cycle might allow fast twitch-type muscle fibres to retain longer the elastic energy stored during the stretching phase and then re-use it during positive phase.

Adult↗

PubMed1986

The effect of extra-load conditioning on muscle performance in athletes.

Fourteen sprinters were assigned to an experimental group (N = 7) and a control group (N = 7) in order to study the effects of 3 wk of extra-load conditioning. The extra-load conditioning was achieved by the athletes wearing special vests containing weights (7-8% body mass). The vests were used from morning to evening and during 3-5 training sessions/wk for 3 wk. No changes in the ordinary training regime were allowed, except the use of the vest by the experimental group. A jumping test battery and short running test on a treadmill were utilized to measure explosive power characteristics and the anaerobic performance of the subjects. While the control group showed no changes in any of the variables studied, the experimental subjects significantly improved their jumping heights in squat jumps with and without extra loads; their jumping heights in drop jumps and mechanical power output in 15 s of jumps. No changes in lactate levels or in running times to exhaustion were observed in response to the extra-load conditioning. The improvement of jumping performances could be due to a fast neurogenic adaptation to the new requirements.

Adaptation, Physiological↗

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

The influence of extra load on the mechanical behavior of skeletal muscle.

Eleven international jumpers and throwers engaged in year round training were divided into experimental (n = 6) and control (n = 5) groups. The experimental group was tested before and after a 3 weeks simulated hypergravity period, and again 4 weeks after the hypergravity period. The high gravity condition was created by wearing a vest weighing about 13% of the subjects body weight. The vest was worn from morning to evening including the training sessions, and only removed during sleep. The daily training of all subjects consisted of classical weight training and jumping drills. No changes in the ordinary training program were allowed in the experimental group, except for the use of the vest. Vertical jumps, drop jumps and a 15 s continuous jumping test were used to measure the explosive power characteristics of the subjects. After the hypergravity period the experimental subjects demonstrated significant (5-10%, P less than 0.05-0.01) improvements in most of the variables studied: however, 4 weeks after cessation of the high gravity period they tended to return towards the starting values. No changes were observed in the results of the control group. The improvement observed in the experimental subjects was explained as fast adaptation to the simulated high gravity field. It is suggested that adaptation had occurred both in neuromuscular functions and in metabolic processes.

Adult↗

PubMed1984

Reproducibility of aerobic and anaerobic thresholds in 20-50 year old men.

The reproducibility of the aerobic (AerT) and the anaerobic (AnT) threshold was studied in 33 men aged 20-50 years. They completed two maximal exercise tests on a bicycle ergometer. The thresholds, as VO2 (1 X min-1), were determined visually by two investigators using both the blood lactate and the respiratory indices. The respiratory variables were measured with a computerized breath-by-breath method; samples of venous blood were drawn every 2nd min and analysed enzymatically for lactate. The reproducibility of the AerT (r = 0.94) and of the AnT (r = 0.96) were equally good. The AnT can be determined either from blood lactate concentrations (AnTLa) or from ventilatory and gas exchange response (AnTr) during a 2-min incremental exercise test. They both also showed similar reproducibility: r = 0.93 for the AnTLa and r = 0.95 for the AnTr. The work rate and the measured physiological variables at the AerT and AnT, except for the blood lactacte concentration, were very reproducible. Age did not affect the reproducibility of the thresholds. The poor reproducibility of blood lactate concentration of the AnT confirmed our previous opinion that the fixed blood lactate levels of 2 and 4 mmol X 1(-1) are poor indicators of AerT and AnT.

Adult↗

PubMed1983

The effect of prolonged skeletal muscle stretch-shortening cycle on recoil of elastic energy and on energy expenditure.

The enhancement of performance in stretch-shortening exercises has been attributed to the recoil of elastic energy stored during the stretching phase. If the time between stretching and shortening (coupling time) is too long the stored elastic energy can be wasted. In the present study, coupling time was increased by asking ten male subjects to run on a treadmill at different speeds (2.2-5.2 m X s-1) using special soft shoes in addition to normal shoes. The results indicated that running with soft shoes required greater energy consumption than running with normal shoes except at slow speed (2.2 m X s-1). When the running speed was increased the extra energy consumed using soft shoes was parallelly enhanced (0.4 J X kg-1/step at 5.2 m X s-1). It was suggested that the effect of coupling time as limiting factor for recoil of elastic energy was relevant in fast twitch (FT) fibers, which were progressively recruited when the running speed was increased. This is consistent to the fact that cross-bridge life time in FT fibers is very short, and therefore more sensitive to coupling time. At slow running speed (2.2 m X s-1) only slow twitch (ST) fibers were recruited and the enhancement of coupling time was not long enough to provocate detachment of cross-bridges of ST fibers, which possess a long cross-bridge life time. It was concluded that the different recruitment of ST and FT fibers influenced the pattern of recoil of elastic energy which was dependent on the running speed.

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

Anaerobic threshold, skeletal muscle enzymes and fiber composition in young female cross-country skiers.

Anaerobic threshold (AT) and maximum oxygen uptake (max VO2) were determined in 15 young female cross-country skiers, aged 15--20 years, during incremental bycycle ergometer exercise. Succinate dehydrogenase (SDH), malate dehydrogenase (MDH), citrate synthase (CS) and lactate dehydrogenase (LDH) were analyzed biochemically and percentage of slow twitch fibres (%ST fibres, myosin adenosine triphosphatase staining) histochemically in muscle samples obtained from m. vastus lateralis. Max VO2 correlated significantly with anaerobic threshold in ml x kg-1 x min-1 (mlAT) but when AT was expressed in percent of max VO2 (%AT) the correlation was insignificant. Significant correlations were found between %AT and SDH (r = 0.63) and between mlAT and CS (r = 0.58). Max VO2 showed no significant correlations with the enzymes studied or %ST fibres. The results of the study seem to support the hypothesis that anaerobic threshold is related to oxidative capacity of muscle.

Adolescent↗