| 1. |
- Balsom, Paul, et al.
(författare)
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Maximal-Intensity Intermittent Exercise: Effect of Recovery Duration
- 1992
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Ingår i: International Journal of Sports Medicine. - 0172-4622 .- 1439-3964. ; 13:7, s. 528-533
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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)
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Physiological responses to maximal intensity intermittent exercise
- 1992
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Ingår i: European Journal of Applied Physiology and Occupational Physiology. - 0301-5548 .- 1432-1025. ; 65, s. 144-149
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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. |
- Bonnard, M, et al.
(författare)
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Different strategies to compensate for the effects of fatigue revealed by neuromuscular adaptation processes in humans.
- 1994
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Ingår i: Neuroscience Letters. - 0304-3940 .- 1872-7972. ; 166:1, s. 101-5
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Tidskriftsartikel (refereegranskat)abstract
- An initially submaximal hopping task was maintained with the same global power output until it became the maximal performance; since there was no decrease in performance, any change in behavior occurring with fatigue characterizes the strategies allowing to compensate for the effects of fatigue. In a prolonged hopping task, fatigue is likely to be most prominent in the ankle extensor muscles since they are the main contributors to vertical propulsion in the hop. With fatigue, all subjects landed with more flexed knees and with an increased activity in the biarticular rectus femoris muscle indicating some compensation between the knee and ankle joint. Furthermore, two different strategies appeared to further compensate for the important fatigue of the ankle extensor muscles: one was organized across joints and consisted in a heavier reliance of the knee extensor vastus lateralis, and the other was organized within the fatigued joint and consisted in an earlier preactivation of the gastrocnemius. As a consequence, two different adaptations of the ground reaction force profiles appeared at the end of the session; each being related to one of these two strategies.
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| 4. |
- Cresswell, A G, et al.
(författare)
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Changes in intra-abdominal pressure, trunk muscle activation and force during isokinetic lifting and lowering.
- 1994
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Ingår i: European Journal of Applied Physiology and Occupational Physiology. - 0301-5548 .- 1432-1025. ; 68:4, s. 315-21
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Tidskriftsartikel (refereegranskat)abstract
- Intra-abdominal pressure (IAP), force and electromyographic (EMG) activity from the abdominal (intra-muscular) and trunk extensor (surface) muscles were measured in seven male subjects during maximal and sub-maximal sagittal lifting and lowering with straight arms and legs. An isokinetic dynamometer was used to provide five constant velocities (0.12-0.96 m.s-1) of lifting (pulling against the resistance of the motor) and lowering (resisting the downward pull of the motor). For the maximal efforts, position-specific lowering force was greater than lifting force at each respective velocity. In contrast, corresponding IAPs during lowering were less than those during lifting. Highest mean force occurred during slow lowering (1547 N at 0.24 m.s-1) while highest IAP occurred during the fastest lifts (17.8 kPa at 0.48-0.96 m.s-1). Among the abdominal muscles, the highest level of activity and the best correlation to variations in IAP (r = 0.970 over velocities) was demonstrated by the transversus abdominis muscle. At each velocity the EMG activity of the primary trunk and hip extensors was less during lowering (eccentric muscle action) than lifting (concentric muscle action) despite higher levels of force (r between -0.896 and -0.851). Sub-maximal efforts resulted in IAP increasing linearly with increasing lifting or lowering force (r = 0.918 and 0.882, respectively). However, at any given force IAP was less during lowering than lifting. This difference was negated if force and IAP were expressed relative to their respective lifting and lowering maxima.(ABSTRACT TRUNCATED AT 250 WORDS)
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| 5. |
- Cresswell, A G, et al.
(författare)
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Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man.
- 1992
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 144:4, s. 409-18
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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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| 6. |
- Cresswell, A G, et al.
(författare)
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The effect of an abdominal muscle training program on intra-abdominal pressure.
- 1994
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Ingår i: Scandinavian Journal of Rehabilitation Medicine. - 0036-5505 .- 1940-2228. ; 26:2, s. 79-86
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Tidskriftsartikel (refereegranskat)abstract
- The effect of 10 weeks' specific abdominal strength training (resisted trunk rotations) on intra-abdominal pressure was investigated in 10 healthy males. Isometric rotational force, trunk flexor and extensor torque and intra-abdominal pressure were measured as well as intra-abdominal pressure responses to Valsalva manoeuvres, maximal pulsed pressures, drop jumps and trunk perturbations. The rotational strength increased 29.7% after training without significant change in intra-abdominal pressure. The isometric flexor strength did not change, while the extensor strength increased 11.0%. Valsalva and pulsed pressures increased 11.6 and 9.2%, respectively. The rate of intra-abdominal pressure development during pulsed pressures, drop jumps and trunk perturbations increased after training. The level of intra-abdominal pressure during the latter two tasks remained unchanged. It is concluded that an increase in strength of the trunk rotators with training improves the ability to generate higher levels of voluntarily induced intra-abdominal pressure and increases the rate of intra-abdominal pressure development during functional situations.
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| 7. |
- Cresswell, A G, et al.
(författare)
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The influence of sudden perturbations on trunk muscle activity and intra-abdominal pressure while standing.
- 1994
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Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 98:2, s. 336-41
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Tidskriftsartikel (refereegranskat)abstract
- Unexpected ventral and dorsal perturbations and expected, self-induced ventral perturbations were delivered to the trunk by suddenly loading a vest strapped to the torso. Six male subjects were measured for intra-abdominal pressure (IAP) and intra-muscular electromyography of the transversus abdominis (TrA), obliquus internus abdominis (OI), obliquus externus abdominis (OE) and rectus abdominis (RA) muscles. Erector spinae (ES) activity was recorded using surface electromyography. Displacements of the trunk and head were registered using a video-based system. Unexpected ventral loading produced activity in TrA, OI, OE and RA, and an IAP increase well in advance of activity from ES. Expected ventral loading produced pre-activation of all muscles and an increased IAP prior to the perturbation. The TrA was always the first muscle active in both the unexpected and self-loading conditions. Of the two ventral loading conditions, forward displacement of the trunk was significantly reduced during the self-loading. Unexpected dorsal loading produced coincident activation of TrA, OI, OE, RA and ES. These results indicate a response of the trunk muscles to sudden expected and unexpected ventral loadings other than the anticipated immediate extensor torque production through ES activation. It is suggested that the increase in IAP is a mechanism designed to improve the stability of the trunk through a stiffening of the whole segment.
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| 8. |
- Fuchi, Tokio, et al.
(författare)
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Microdialysis of rat skeletal muscle and adipose tissue : dynamics of the interstitial glucose pool.
- 1994
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 151:2, s. 249-60
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Tidskriftsartikel (refereegranskat)abstract
- Microdialysis was evaluated as a method for studying glucose metabolism in skeletal muscle. Dialysis probes (0.5 x 10 mm) were perfused at 0.5 or 1.0 microliter min-1. Based upon perfusion with glucose, the muscle interstitial glucose concentration was estimated to be 6.9 +/- 0.3 mM (n = 14), which was not significantly different from the blood glucose level. With insulin infusion (1200 mU kg-1 body wt i.v.), the insulin-induced change in the glucose concentration of the interstitial space of muscle was of equal magnitude to that of blood and adipose tissue. In spite of this, when the perfusion medium was not supplemented with glucose, the glucose concentration decreased more in skeletal muscle dialysates (to 36.7 +/- 4.9% of the initial level) than in blood (to 29.7 +/- 5.0%) but less than in adipose tissue (to 17.7 +/- 4.9% of the initial level) (P < 0.05). The results indicate that these differences are due to tissue-specific differences in the dynamic balance between the supply to, and removal from, the interstitial glucose pool. This balance is revealed as a result of the constant glucose drainage by the microdialysis probe. The present results show that, in skeletal muscle, increases in glucose uptake occur with a concomitant increase in tissue blood flow as revealed by the microdialysis ethanol technique, whereas in adipose tissue the glucose uptake increases in the absence of a corresponding increase in blood flow.
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| 9. |
- Hassmén, Peter, et al.
(författare)
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Branched-chain amino acid supplementation during 30-km competitive run : mood and cognitive performance.
- 1994
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Ingår i: Nutrition (Burbank, Los Angeles County, Calif.). - 0899-9007 .- 1873-1244. ; 10:5, s. 405-10
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that an elevated concentration of the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) in specific areas of the brain may contribute to the development of central/mental fatigue during and after sustained exercise. Supplementation with branched-chain amino acids (BCAAs) should prevent the exercise-induced increase in the plasma concentration ratio of free tryptophan to other large neutral amino acids (including BCAAs) and thereby prevent an elevation in the level of 5-HT in the brain. In this study, subjects were given either a mixture of BCAAs in a carbohydrate solution or a placebo drink that contained only carbohydrates during a 30-km cross-country race. Several tasks to measure cognitive performance were performed before and after the race. When subjects were supplied with BCAAs, their performance in the different parts of the color-word test (words, colors and color words) was improved by an average of 3-7% (p < 0.05) after exercise, whereas there was no difference in performance before and after exercise in the subjects who were given the placebo. Furthermore, the experimental group, supplied with BCAAs, maintained their performance in the shape-rotation and figure-identification tasks, whereas an impairment in performance in these tests by 25% (p < 0.05) and 15% (p < 0.05), respectively, was found in the subjects who received the placebo. Thus, BCAA supplementation seemed to have an effect on the more complex tasks, whereas no effect could be detected on the less demanding tasks. However, an intake of BCAAs during exercise modified only slightly the exercise-induced changes in mood.
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| 10. |
- Hassmén, Peter, et al.
(författare)
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Mood change and marathon running : a pilot study using a Swedish version of the POMS test.
- 1991
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Ingår i: Scandinavian Journal of Psychology. - : Wiley. - 0036-5564 .- 1467-9450. ; 32:3, s. 225-32
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Tidskriftsartikel (refereegranskat)abstract
- Regular exercise is said to have positive effects on mood, especially if the exercise intensity is low to moderate. However, the acute effects resulting from participation in a strenuous competition, such as a marathon race, have been studied less. The present investigation used the Profile of Mood States (POMS) test to measure mood, before and after the 1989 Stockholm Marathon. A total of 106 male runners (mean age 40.0 years), with finishing times between 3h and 3h 45 min participated as subjects. Results showed great changes between pre- and post-marathon scores, most of them significant at the p less than 0.001 level. Furthermore, differences between a faster and a slower group of runners were demonstrated with regard to mood states, even though plasma glucose levels were comparable. It is concluded that participation in a marathon race greatly effects mood, mainly in a more negative way than low to moderately intense exercise does.
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