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Sökning: WAKA:ref > Gymnastik- och idrottshögskolan > (1990-1994) > (1992)

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1.
  • Balsom, Paul, et al. (författare)
  • Maximal-Intensity Intermittent Exercise: Effect of Recovery Duration
  • 1992
  • Ingår i: International Journal of Sports Medicine. - 0172-4622 .- 1439-3964. ; 13:7, s. 528-533
  • Tidskriftsartikel (refereegranskat)abstract
    • Seven male subjects performed 15 x 40m sprints, on three occasions, with rest periods of either 120 s (R120), 60 s (R60) or 30 s (R30) between each sprint. Sprint times were recorded with four photo cells placed at 0, 15, 30 and 40 m. The performance data indicated that whereas running speed over the last 10 m of each sprint decreased in all three protocols (after 11 sprints in R120, 7 sprints in R60 and 3 sprints in R30), performance during the initial acceleration period from 0-15 m was only affected with the shortest rest periods increasing from (mean +/- SEM) 2.58 +/- .03 (sprint 1) to 2.78 +/- .04 s (spring 15) (p < .05). Post-exercise blood lactate concentration was not significantly different in R120 (12.1 +/- 1.3 mmol.l-1) and R60 (13.9 +/- 1.2 mmol.l-1), but a higher concentration was found in R30 (17.2 +/- .7 mmol.l-1) (p < .05). After 6 sprints there was no significant difference in blood lactate concentration with the different recovery durations, however, there were significant differences in sprint times at this point, suggesting that blood lactate is a poor predictor of performance during this type of exercise. Although the work bouts could be classified primarily as anaerobic exercise, oxygen uptake measured during rest periods increased to 52, 57 and 66% of maximum oxygen uptake in R120, R60 and R30, respectively. Evidence of adenine nucleotide degradation was provided by plasma hypoxanthine and uric acid concentrations elevated post-exercise in all three protocols. Post-exercise uric acid concentration was not significantly affected by recovery duration.(ABSTRACT TRUNCATED AT 250 WORDS)
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2.
  • Balsom, Paul, et al. (författare)
  • Physiological responses to maximal intensity intermittent exercise
  • 1992
  • Ingår i: European Journal of Applied Physiology and Occupational Physiology. - 0301-5548 .- 1432-1025. ; 65, s. 144-149
  • Tidskriftsartikel (refereegranskat)abstract
    • Physiological responses to repeated bouts of short duration maximal-intensity exercise were evaluated. Seven male subjects performed three exercise protocols, on separate days, with either 15 (S15), 30 (S30) or 40 (S40) m sprints repeated every 30 s. Plasma hypoxanthine (HX) and uric acid (UA), and blood lactate concentrations were evaluated pre- and postexercise. Oxygen uptake was measured immediately after the last sprint in each protocol. Sprint times were recorded to analyse changes in performance over the trials. Mean plasma concentrations of HX and UA increased during S30 and S40 (P less than 0.05), HX increasing from 2.9 (SEM 1.0) and 4.1 (SEM 0.9), to 25.4 (SEM 7.8) and 42.7 (SEM 7.5) mumol.l-1, and UA from 372.8 (SEM 19) and 382.8 (SEM 26), to 458.7 (SEM 40) and 534.6 (SEM 37) mumol.l-1, respectively. Postexercise blood lactate concentrations were higher than pretest values in all three protocols (P less than 0.05), increasing to 6.8 (SEM 1.5), 13.9 (SEM 1.7) and 16.8 (SEM 1.1) mmol.l-1 in S15, S30 and S40, respectively. There was no significant difference between oxygen uptake immediately after S30 [3.2 (SEM 0.1) l.min-1] and S40 [3.3 (SEM 0.4) l.min-1], but a lower value [2.6 (SEM 0.1) l.min-1] was found after S15 (P less than 0.05). The time of the last sprint [2.63 (SEM 0.04) s] in S15 was not significantly different from that of the first [2.62 (SEM 0.02) s]. However, in S30 and S40 sprint times increased from 4.46 (SEM 0.04) and 5.61 (SEM 0.07) s (first) to 4.66 (SEM 0.05) and 6.19 (SEM 0.09) s (last), respectively (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS
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3.
  • Cresswell, A G, et al. (författare)
  • Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man.
  • 1992
  • Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 144:4, s. 409-18
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim was to investigate possible relationships between activities of the individual muscles of the ventrolateral abdominal wall and the development of pressure within the abdominal cavity. Intra-muscular activity was recorded bilaterally from transversus abdominis, obliquus internus, obliquus externus and rectus abdominis with fine-wire electrodes guided into place using real-time ultrasound. Intra-abdominal pressure was measured intragastrically using a micro tip pressure transducer. Six males were studied during loading and movement tasks with varied levels of intra-abdominal pressure. During both maximal voluntary isometric trunk flexion and extension, transversus abdominis activity and intra-abdominal pressure remained constant, while all other abdominal muscles showed a marked reduction during extension. When maximal isometric trunk flexor or extensor torques were imposed upon a maximal Valsalva manoeuvre, transversus abdominis activity and intra-abdominal pressure remained comparable within and across conditions, whereas obliquus internus, obliquus externus and rectus abdominis activities either markedly increased (flexion) or decreased (extension). Trunk twisting movements showed reciprocal patterns of activity between the left and right sides of transversus abdominis, indicating an ability for torque development. During trunk flexion--extension, transversus abdominis showed less distinguished changes of activity possibly relating to a general stabilizing function. In varied pulsed Valsalva manoeuvres, changes in peak intra-abdominal pressure were correlated with mean amplitude electromyograms of all abdominal muscles, excluding rectus abdominis. It is concluded that the co-ordinative patterns shown between the muscles of the ventrolateral abdominal wall are task specific based upon demands of movement, torque and stabilization. It appears that transversus abdominis is the abdominal muscle whose activity is most consistently related to changes in intra-abdominal pressure.
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4.
  • Hickner, R C, et al. (författare)
  • The ethanol technique of monitoring local blood flow changes in rat skeletal muscle : implications for microdialysis.
  • 1992
  • Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 146:1, s. 87-97
  • Tidskriftsartikel (refereegranskat)abstract
    • We have investigated the feasibility of monitoring local skeletal muscle blood flow in the rat by including ethanol in the perfusion medium passing through a microdialysis probe placed in muscle tissue. Ethanol at 5, 55, or 1100 mM did not directly influence local muscle metabolism, as measured by dialysate glucose, lactate, and glycerol concentrations. The clearance of ethanol from the perfusion medium can be described by the outflow/inflow ratio ([ethanol]collected dialysate/[ethanol]infused perfusion medium), which was found to be similar (between 0.36 and 0.38) at all ethanol perfusion concentrations studied. With probes inserted in a flow-chamber, this ratio changed in a flow-dependent way in the external flow range of 5-20 microliters min-1. The ethanol outflow/inflow ratio in vivo was significantly (P less than 0.001) increased (to a maximum of 127 +/- 2.8% and 144 +/- 7.4% of the baseline, mean +/- SEM) when blood flow was reduced by either leg constriction or local vasopressin administration, and significantly (P less than 0.001) reduced (to 62 +/- 6.4% and 43 +/- 4.4% of baseline) with increases in blood flow during external heating or local 2-chloroadenosine administration, respectively. Dialysate glucose concentrations correlated negatively with the ethanol outflow/inflow ratio (P less than 0.01) and consequently decreased (to 46 +/- 7.6% and 56 +/- 5.6% of baseline) with constriction and vasopressin administration and increased (to 169 +/- 32.5% and 262 +/- 16.7% of baseline) following heating and 2-chloroadenosine administration. Dialysate lactate concentrations were significantly increased (approximately 2-fold, P less than 0.001) during all perturbations of blood flow. In conclusion, this technique makes it possible to monitor changes in skeletal muscle blood flow; however, methods of quantification remain to be established. The fact that blood flow changes were found to significantly affect interstitial glucose and lactate concentrations as revealed by microdialysis indicates that this information is critical in microdialysis experiments.
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5.
  • Svedenhag, Jan, et al. (författare)
  • Running on land and in water: comparative exercise physiology
  • 1992
  • Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 24:10, s. 1155-1160
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of water immersion on cardiorespiratory and blood lactate responses during running was investigated. Wearing a buoyant vest, 10 trained runners (mean age 26 yr) ran in water at four different and specified submaximal loads (target heart rates 115, 130, 145, and 155-160 beats.min-1) and at maximal exercise intensity. Oxygen uptakes (VO2), heart rates, perceived exertion, and blood lactate concentrations were measured. Values were compared with levels obtained during treadmill running. For a given VO2, heart rate was 8-11 beats.min-1 lower during water running than during treadmill running, irrespective of exercise intensity. Both the maximal oxygen uptake (4.03 vs 4.60 1 x min-1) and heart rate (172 vs 188 beats.min-1) were lower during water running. Perceived exertion (legs and breathing) and the respiratory exchange ratio (RER) were higher during submaximal water running than during treadmill running, while ventilation (1 x min-1) was similar. The blood lactate concentrations were consistently higher in water than on the treadmill, both when related to VO2 and to %VO2max. Partly in conformity with earlier cycle ergometer studies, these data suggest that immersion induces acute cardiac adjustments that extend up to the maximal exercise level. Furthermore, both the external hydrostatic load and an altered running technique may add to an increased anaerobic metabolism during supported water running.
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7.
  • Åstrand, PO (författare)
  • J.B. Wolffe Memorial Lecture. "Why exercise?".
  • 1992
  • Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 24:2, s. 153-62
  • Tidskriftsartikel (refereegranskat)abstract
    • There is a pronounced plasticity and adaptability in the structural and/or functional properties of cells, tissues, and organ systems in the human body when exposed to various stimuli. While there is unanimous agreement that regular exercise is essential for optimal function of the human body, it is evident that extrinsic factors, such as diet and exercise habits, are reflected in the morbidity and mortality statistics, especially in the aged. Aging is obligatorily associated with reduced maximal aerobic power and reduced muscle strength, i.e., with reduced physical fitness. As a consequence of diminished exercise tolerance, a large and increasing number of elderly persons will be living below, at, or just above "thresholds" of physical ability, needing only a minor intercurrent illness to render them completely dependent. Physical training can readily produce a profound improvement of functions essential for physical fitness in old age. Adaptability to regular physical activity serves to cause less disruption of the cell's "milieu interieur" and minimizes fatigue, thereby enhancing performance and the economy of energy output during exercise.
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8.
  • Åstrand, PO (författare)
  • Physical activity and fitness.
  • 1992
  • Ingår i: American Journal of Clinical Nutrition. - 0002-9165 .- 1938-3207. ; 55:6 Suppl, s. 1231S-1236S
  • Tidskriftsartikel (refereegranskat)abstract
    • There is unanimous agreement that regular exercise is essential for optimal function of the human body. It is evident that extrinsic factors, such as diet and exercise habits, are reflected in the morbidity and mortality statistics, especially in aging. Aging is obligatorily associated with reduced maximal aerobic power and reduced muscle strength, ie, with reduced physical fitness. As a consequence of diminished exercise tolerance, a large and increasing number of elderly people will be living below, at, or just above "thresholds" of physical ability, needing only a minor intercurrent illness to render them completely dependent. Physical training can readily produce a profound improvement of functions also essential for physical fitness in old age. From a nutritional viewpoint one advantage of physical activity, and increased metabolic rate, is that a higher energy intake can better secure an adequate intake of essential nutrients.
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