Biomedical subjects
Publications and source records attributed to P Luhtanen.
This study examined the relationship between cohesion measured by the Group Environment Questionnaire and success measured by winning percentage with over 200 junior ice hockey players. The cohesion explained 29% of the variance of the success. Scores on task cohesion were better predictors of success than social cohesion.
Physically active men (n = 13) twice performed the Maximal Anaerobic Running Test (MART) on a treadmill and once the Wingate Anaerobic Test (WAnT) on a cycle ergometer. The MART consisted of n 20-s runs with 100-s recovery between the runs. The speed of the first run was 14.6 km.h-1 and the inclination 4 degrees. Thereafter, the speed was increased by 1.37 km.h-1 every run until exhaustion. During all tests oxygen uptake was measured breath-by-breath and blood samples were taken from the fingertip 40s after each run to determine the lactate concentration (BLa). Power at submaximal BLa levels and maximal power (P5mM, P10mM and Pmax, respectively) were calculated and P was expressed as the oxygen demand of running according to the American College of Sports Medicine equation. In the MART the Pmax was 108 ml.kg-1.min-1 and peak BLa was 15.6 mM. The reliability for the power indices in the MART were as follows: r = 0.92 (p < 0.001) for Pmax r = 0.80 (p < 0.001) for P10mM and r = 0.67 (p = 0.01) for P5mM. The average contribution of anaerobic energy expenditure was calculated to be 68% but it ranged from 64% to 72% during the MART. Although four out of seven of the correlations between the corresponding variables of the MART and WAnT were significant (0.52 < r < 0.59) they were not high. It is concluded that the anaerobic energy production is high in the MART, the test is reliable, and that the treadmill and cycle ergometer test measure slightly different qualities.
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.
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)
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.
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.
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.
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 statis position = SJ, with counter-movement equal CMJ and after a fall from different heights equal DJ) and (3) a new anaerobic test (Bosco 1983a). This consisted of performing continuous jump work for a certain period of time (e.g., 60 s). Both ballistic activities and anaerobic power tests demonstrated the highest relationship with peak torques when this was developed respectively at pi and 4.2 rad x s-1. Peak torque was related to SJ (r = 0.71, p less than 0.01); to CMJ (r = 0.74, p less than 0.005); to best DJ (r = 0.60, p less than 0.05), to 15 s anaerobic power (r = 0.70, p less than 0.01) and 60 s anaerobic power (r = 0.68, p less than 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.
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.
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Ground reaction forces and mechanical power were investigated when the subjects walked normally, while they were racing or running at four speeds, and when they performed the running long jump take-off. In addition, the apparent spring constants of the support leg in eccentric and concentric phases were investigated at the four running speeds, during the running long jump take-off, and in the triple jump. Six club level track and field athletes, four national level long jumpers, and six national level triple jumpers took part in the study. Cinematographic technique and a mathematical model of hopping (Alexander and Vernon 1975) were employed in the analysis. Force and power values were found to vary in the following order (from highest to lowest): long jump take-off, maximal running speed, submaximal running (80, 60, and 40% of maximum speed), racing gait, and normal gait. The data disclosed that the measured parameters had the highest values in the long jump take-off performed by the long jump athletes. Their peak values were: resultant ground reaction force 3270 +/- 74 N and mechanical power 160.1 +/- 10.5 J x kg-1 x s-1. For the track and field athletes the values were 2010 +/- 80 N and 126.0 +/0 12.6 J x kg-1 x s-1. The apparent spring constant values of the support leg in the national level jumper group were in eccentric phase 30.54 +/- 8.38 N x mm-1 x kg-1 and in concentric phase 0.129 +/- 0.012 N x mm-1 x kg-1. In the track and field athletes the values were 13.97 +/- 1.01 N x mm-1 x kg-1 and 0.093 +/- 0.003 N x mm-1 x kg-1, respectively. In general, the increase in force and mechanical power output was related to the value of the apparent spring constant of the support leg in the eccentric phase. The spring constant in the eccentric phase increased with the velocity of motion in running, the long jump take-off and the triple jump. This suggests that it may be possible to use this parameter as a measure of mechanical performance, as it may reflect the combined elasticity of muscles, tendons, and bones.
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Changes in total mechanical work, its partitioning into different energy states, mechanical power, force-time characteristics, force impulses of body segments and mass center's pathway characteristics during long jump take-off were investigated on four national and six ordinary level athletes. Both cinematographic and force-platform techniques were used. The data showed that the national level jumpers had higher run-up and higher take-off (release) velocities in horizontal and vertical directions. In addition, they were able to utilize efficiently the elastic energy stored in the leg extensor muscles at take-off impact. This was seen in high support leg eccentric and concentric forces, which were produced in short contact times. The ordinary level athletes had greater variability in the investigated attributes, and they reached their maximum length of jumps in many different ways. Cinematically the greatest difference between the subject groups was observed in the timing of the various body segment movements. In better athletes all the body parts (arms, trunk, and legs) had decelerating horizontal impulses, but in all ordinary level athletes the horizontal impulse of the swing leg was accelerating during take-off.
Performance of a vertical jump was analyzed with respect to the contribution of the different body segments to the forces acting on the whole body center of gravity. Both cinematograph and force-platform techniques were employed. The data disclosed that the take-off velocity in vertical jumps was caused by the different components as follows: knee extension 56%, plantar flexion 22%, trunk extension 10%, arm swing 10%, and head swing 2%. However, the average take-off velocity of the total performance (3.03 m/s) was only 76% from the theoretical maximum calculated from the segmental analyses. Optimal timing of the segmental performances was calculated to increase this "efficiency" to 84%. Great variance were observed among individuals in the total performance despite the similarities in utilization of the performance of individual segments.
Changes in total mechanical work and its partitioning into different energy states (kinetic, potential and rotational) during a step cycle of running were investigated on six well trained athletes who ran at the test speeds of 40, 60, 80, and 100% (9.3 +/- 0.3 m/s) of maximum. Cinematographic techniques were utilized to calculate the mechanical energy states as described by Norman et al. (1976), using a 13 segment mechanical model of a runner as the basis for the computations. The data showed that both the kinetic and rotational energy increased parabolically but the potential energy decreased linearly with increases in running velocity. The calculated power of the positive work phase increased quadratically with running speed. During the phase when the runner was in contact with the ground, the applied calculations gave similar increases for the positive and negative works, and the power ratio (Wneg/Wpos) stayed the same at all measured speeds. Therefore, it is likely that the method used to calculate the various mechanical energy states did not reflect accurately enough the physiological energy costs at higher running speeds. It may, however, be quite acceptable for estimating the mechanical energy states during walking and slow running, in which case the role of negative work is less and consequently the storage and utilization of elastic energy is small.
The effects of an 8 weeks period of systematic progressive strength training on the EMG activity of the leg extensor muscles (vastus lateralis and rectus femoris) were investigated in 8 healthy male subjects (22-31 yrs). After training there were indications (n.s.) of a decline in integrated EMG (IEMG) during maximal isometric knee extension as well as in the IEMG vs isometric force relationship. The averaged motor unit potential (AMUP) did not demonstrate any significant changes due to the strength training regimen. In conformity with earlier findings no or only minor alterations were observed in anthropometrics, muscle enzyme activities and fibre composition. The fibre area ratio indicated a specific effect of the training stimuli on the fast twitch muscle fibres. Thus, EMG-analyses, as employed in the present study, did not provide any conclusive additional explanation as to the mechanisms behind the well established gains in muscle strength performance induced by the applied strength training program.