Biomedical subjects

Jostein Hallén

Publications and source records attributed to Jostein Hallén.

9 recordsLinked to original sources

PubMed2006

Live high-train low for 24 days increases hemoglobin mass and red cell volume in elite endurance athletes.

The effect of live high-train low on hemoglobin mass (Hbmass) and red cell volume (RCV) in elite endurance athletes is still controversial. We expected that Hb(mass) and RCV would increase, when using a presumably adequate hypoxic dose. An altitude group (AG) of 10 Swiss national team orienteers (5 men and 5 women) lived at 2,500 m (18 h per day) and trained at 1,800 and 1,000 m above sea level for 24 days. Before and after altitude, Hbmass, RCV (carbon monoxide rebreathing method), blood, iron, and performance parameters were determined. Seven Swiss national team cross-country skiers (3 men and 4 women) served as "sea level" (500-1,600 m) control group (CG) for the changes in Hbmass and RCV. The AG increased Hbmass (805+/-209 vs. 848+/-225 g; P<0.01) and RCV (2,353+/-611 vs. 2,470+/-653 ml; P<0.01), whereas there was no change for the CG (Hbmass: 849+/-197 vs. 858+/-205 g; RCV: 2,373+/-536 vs. 2,387+/-551 ml). Serum erythropoietin (P<0.001), reticulocytes (P<0.001), transferrin (P<0.001), soluble transferrin receptor (P<0.05), and hematocrit (P<0.01) increased, whereas ferritin (P<0.05) decreased in the AG. These changes were associated with an increased maximal oxygen uptake (3,515+/-837 vs. 3,660+/-770 ml/min; P<0.05) and improved 5,000-m running times (1,098+/-104 vs. 1,080+/-98 s; P<0.01) from pre- to postaltitude. Living at 2,500 m and training at lower altitudes for 24 days increases Hbmass and RCV. These changes may contribute to enhance performance of elite endurance athletes.

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PubMed2006

Physical fitness and physical training during Norwegian military service.

OBJECTIVE: Evaluate the physical fitness and training of Norwegian infantry soldiers during 10 months of compulsory military service. METHODS: Maximal oxygen uptake (VO2max) and maximal numbers of sit-ups, push-ups, and chin-ups and 3-km running time were tested in 107 male infantry soldiers at the beginning and end of basic training (BT), and again at demobilization. The amount of physical training was registered throughout the military service. RESULTS: During BT, major improvements in sit-ups and push-ups were found. VO2max increased in soldiers with the lowest initial VO2max, but decreased to pre-BT level at demobilization. The amount of obligatory physical training was 8.5 hours x week(-1) during BT and 35% lower after BT, and was usually performed in uniform at low to moderate intensity. CONCLUSION: The amount of high-intensity endurance and strength training during compulsory military service is to low to improve the soldiers' endurance and muscular strength.

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PubMed2005

Linear decrease in .VO2max and performance with increasing altitude in endurance athletes.

It has been hypothesized that one reason for decreased .VO(2max) in hypoxia could be the lower maximal exercise intensity achieved in incremental, time or distance trial tests. We hypothesized that (1).VO(2max) would be decreased at altitude even when exercising at the same absolute maximal exercise intensity as at sea level and; (2) the decline in .VO(2max) in endurance-trained athletes (ETA) would be linear across the range from sea level through moderate altitudes. Eight ETA performed combined .VO(2max) and performance tests running to exhaustion at the same speed in a randomized double blind fashion at simulated altitudes of 300, 800, 1,300, 1,800, 2,300 and 2,800 m above sea level using a hypobaric chamber. Douglas bag system was used for respiratory measurements and pulse oximetry was used to estimate arterial O(2) saturation. .VO(2max) declined linearly from 66+/-1.6 ml kg(-1) min(-1) at 300 m to 55+/-1.6 ml kg(-1) min(-1) at 2,800 m corresponding to a 6.3% decrease per 1,000 m increasing altitude (range 4.6-7.5%). Time to exhaustion (performance) at a constant velocity associated with 107% of sea level .VO(2max) decreased with 14.5% (P<0.001) per 1,000 m altitude between 300 and 2,800 m. Both .VO(2max) and performance decreased from 300 to 800 m (P<0.01; P<0.05). Arterial haemoglobin oxygen saturation at test cessation (SpO(2min)) declined from 89.0+/-2.9% at 300 m to 76.5+/-4.0% at 2,800 m (P=0.001). This study report that in ETA during acute exposure to altitude both performance and .VO(2max) decline from 300 to 800 m above sea level and continued to decrease linearly to 2,800 m.

Adult↗

PubMed2005

Low-dose GH improves exercise capacity in adults with GH deficiency: effects of a 22-month placebo-controlled, crossover trial.

Fifty-five patients with adult-onset GH deficiency (mean age, 49 years) were enrolled in a placebo-controlled, crossover study to investigate the effects of GH therapy on exercise capacity, body composition, and quality of life (QOL). GH and placebo were administered for 9 months each, separated by a 4-month washout period. GH therapy was individually dosed to obtain an IGF-I concentration within the normal range for age and sex. The final mean daily dose of GH was 1.2 IU/day for men and 1.8 IU/day for women. Mean IGF-I concentration at baseline was higher in men than in women (95+/-33 vs 68+/-41 microg/l respectively; P < 0.04) and increased to a similar level on GH therapy. Body fat mass was reduced by 1.9+/-2.9 kg and lean body mass was increased by 1.8+/-2.8 kg (P = 0.0001 for each) with GH treatment. Total and low-density cholesterol levels decreased. Absolute maximal oxygen uptake increased by 6% (P = 0.01), relative to body weight by 9% (P = 0.004), and there was a trend toward increased endurance performance by 7% (P = 0.07). There were no significant effects on QOL. In conclusion, treatment with a low, physiologic dose of GH produced positive effects on body composition and lipids and improved exercise capacity, likely to be of clinical relevance. No changes in QOL were seen, possibly because of a good QOL at baseline.

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PubMed2004

Cadence and performance in elite cyclists.

Many studies have attempted to describe the optimal cadence in cycling. However, the effect on performance has received little attention. The aim of the present study was therefore to examine the effect of cadence on performance during prolonged cycling (approximately 30 min). Fourteen male elite cyclists performed two or five time trials at different cadences [60, 80, 100, 120 rpm or freely chosen cadence (FCC)]. The total work was the same between the time trials, and the subjects were instructed to complete each time trial as fast as possible by adjusting the workload with buttons mounted on the handlebar. Accumulated work and cadence was visualised on a monitor. Oxygen uptake was measured continuously and blood lactate concentration every fifth minute. Compared to 80 rpm, finishing times at 60, 100 and 120 rpm were 3.5, 1.7 and 10.2% slower (P<0.05). Finishing time at FCC (mean 90 rpm) was indistinguishable from 80 and 100 rpm. Gross efficiency at 80 rpm was 2.9, 2.3, 3.4 and 12.3% larger than at 60, FCC, 100 and 120 rpm, respectively (P<0.05). The maximal energy turnover rate was 1.7% higher at 100 than at 80 rpm (P<0.05). This could not, however, compensate for the 3.4% lower efficiency at 100 rpm. This study demonstrated that elite cyclists perform best at their most efficient cadence despite the maximal energy turnover rate being larger at a higher cadence.

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PubMed2004

The most economical cadence increases with increasing workload.

Several studies have suggested that the most economical cadence in cycling increases with increasing workload. However, none of these studies have been able to demonstrate this relationship with experimental data. The purpose of this study was to test the hypothesis that the most economical cadence in elite cyclists increases with increasing workload and to explore the effect of cadence on performance. Six elite road cyclists performed submaximal and maximal tests at four different cadences (60, 80, 100 and 120 rpm) on separate days. Respiratory data was measured at 0, 50, 125, 200, 275 and 350 W during the submaximal test and at the end of the maximal test. The maximal test was carried out as an incremental test, conducted to reveal differences in maximal oxygen uptake and time to exhaustion (short-term performance) between cadences. The results showed that the lowest oxygen uptake, i.e. the best work economy, shifted from 60 rpm at 0 W to 80 rpm at 350 W ( P<0.05). No difference was found in maximal oxygen uptake among cadences ( P>0.05), while the best performance was attained at the same cadence that elicited the best work economy (80 rpm) at 350 W ( P<0.05). This study demonstrated that the most economical cadence increases with increasing workload in elite cyclists. It was further shown that work economy and performance are related during short efforts (approximately 5 min) over a wide range of cadences.

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PubMed2004

Effects of 20-s and 180-s double poling interval training in cross-country skiers.

The purpose of this study was to investigate the effect of upper body 20-s or 180-s interval training, using a double poling ergometer, on upper body power output and selected physiological and biomechanical parameters in cross-country skiers. Twenty (12 male, 8 female) well-trained cross-country skiers took part. Two intervention groups, a 20-s interval training group (IT20; n=6) and a 180-s interval training group (IT180; n=7), underwent training three times a week for 6 weeks on a double poling ergometer. A third group served as a control (CON; n=7) and followed the same training program as the IT20 and IT180 groups without the double poling ergometer interval training. The IT20 and IT180 groups significantly (P<0.05) increased both peak and mean power in a 30-s test and mean power in a 6-min test after double poling training. There was a significant improvement in work efficiency in both IT20 and IT180 (P<0.05) and, in IT180, a significant reduction (P<0.05) in blood lactate concentration at given sub-maximal workloads. VO(2peak) increased significantly during double poling in IT180 ( P<0.05) only. VO(2max) did not change significantly in either group. There were no significant changes in any of the test variables in CON. In conclusion, this study shows that 6 weeks of 20-s or 180-s double poling interval training, three times a week, significantly increases power output in both 30-s and 6-min tests, as well as in selected physiological and biomechanical parameters in well-trained cross-country skiers.

Adult↗

PubMed2004

Residual effects of prior exercise and recovery on subsequent exercise-induced metabolic responses.

Data on the metabolic responses to repeated endurance exercise sessions are limited. Thus, the aims of this study were to examine (1) the impact of prior exercise on metabolic responses to a subsequent exercise session and (2) the effect of different recovery periods between two daily exercise sessions on metabolic responses to the second bout of exercise. Nine male elite athletes participated in four 25-h trials: one bout of exercise (ONE), two bouts of exercise separated by 3 h of rest and one meal (SHORT), two bouts of exercise separated by 6 h of rest and two meals (LONG), and a trial with no exercise (REST). All exercise bouts consisted of 10 min cycling at 50% followed by 65 min at 75% of maximal O2 uptake. Compared to no prior exercise (ONE), a previous bout of exercise (SHORT) was followed by higher mean O2 uptake, heart rate (HR), rectal temperature (TR), excess post-exercise oxygen consumption and lower respiratory exchange ratio (R) during and after a similar exercise session 3 h later. A longer rest interval between the two exercise bouts (6 h versus 3 h) and an additional meal resulted in a decrease in O2 uptake, HR, TR and an increase in R during the second bout of exercise, but no effects on post-exercise metabolism were found. Thus, augmented metabolic stress was observed when strenuous exercise was repeated after only 3 h of recovery, but this was attenuated when a longer recovery period including an additional meal was provided between the exercise sessions.

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PubMed2003

Delayed leukocytosis after hard strength and endurance exercise: aspects of regulatory mechanisms.

BACKGROUND: During infections, polymorphonuclear neutrophilic granulocytes (PMN) are mobilized from their bone marrow stores, travel with blood to the affected tissue, and kill invading microbes there. The signal(s) from the inflammatory site to the marrow are unknown, even though a number of humoral factors that can mobilize PMN, are well known. We have employed a standardized, non-infectious human model to elucidate relevant PMN mobilizers. Well-trained athletes performed a 60-min strenuous strength workout of leg muscles. Blood samples were drawn before, during and just after exercise, and then repeatedly during the following day. Cortisol, GH, ACTH, complement factors, high-sensitive CRP (muCRP), IL-6, G-CSF, IL-8 (CXCL8) and MIP-1beta (CCL4) were measured in blood samples. PMN chemotaxins in test plasma was assessed with a micropore membrane technique. RESULTS: About 5 hr after the workout, blood granulocytosis peaked to about 150% of baseline. Plasma levels of GH increased significantly 30 min into and 5 min after the exercise, but no increase was recorded for the other hormones. No significant correlation was found between concentrations of stress hormones and the subjects' later occurring PMN increases above their individual baselines. Plasma G-CSF increased significantly - but within the normal range - 65 min after the workout. IL-6 increased very slightly within the normal range, and the chemokines IL-8 and MIP-1beta did not increase consistently. However, we found a significant increase of hitherto non-identified PMN-chemotactic activity in plasma 35, 50, and 60 min after the exercise. No systemic complement activation was detected, and (mu)CRP was within the reference range at rest, 5 h and 23 h after the exercise. After endurance exercise, similar findings were made, except for a cortisol response, especially from non-elite runners. CONCLUSION: Apparently, a multitude of humoral factors can - directly or indirectly - mobilize PMN from marrow to blood; some of the factors are, others are not known to be, chemotactic. Under different conditions, different selections of these mobilizers may be used. In the late granulocytosis after heavy, long-lasting exercise a number of factors thought capable of mimicking the granulocytosis of infectious diseases were apparently irrelevant.

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