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- Björklund, Glenn, et al.
(författare)
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A comparison between elite and well trained cross-country skiers in physiological response to variations in intensity during prolonged exercise
- 2008
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Ingår i: 13th Annual Congress of the European College of Sports Science. - Cologne : Sportools. - 9789727351565 ; , s. 522-
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Konferensbidrag (refereegranskat)abstract
- Introduction: Cross-country ski racing includes continual variations in intensity due to terrain and tactics {Mygind et al 1994; Norman et al 1989). Consequently, the recovery between periods with higher intensity might affect the outcome of the race. Both blood metabolites and respiratory variables are used for standard performance evaluations for endurance athletes, although there is a lack information if respiratory variables respond similar to blood lactate and acid/base values during prolonged variable exercise. Therefore, the aims with the present study were to 1) evaluate whether respiratory variables are associated with blood lactate and acid/base variables, 2) how/if these variables might predict physical performance and 3) whether a calculated heart rate-oxygen uptake (HR-VO2) relationship is valid during variable intensity exercise. Methods: 12 cross-country skiers classified as elite (E, n=6) and formerly well-trained (FWT, n=6) performed two roller ski tests. 1) An incremental test to establish maximal oxygen uptake (VO2max), maximum heart rate (HRmax) and lactate threshold (LT). Submaximal and maximal VO2 and HR during the incremental test were used for calculating the individual HR-VO2 linear relationship and 2) a 48-min long variable intensity protocol (VIP) at alternating exercise intensities, 90% (HI90) and 70% (MI70) of VO2max. Cardio-respiratory variables and venous blood samples were continuously collected throughout the VIP. Comparisons between E and FWT were performed using a two-tailed unpaired Student’s t-test and a ANCOVA analysis was used to determine which physiological variable best could prognosticate time to exhaustion (TTE). A simple linear regression was used to establish the relationship between HR and VO2. Results: Blood lactate concentrations [La] were higher and base excess [BE] lower for FWT from the first MI70 (P<0.05). FWT had augmented RER during all HI90 and an elevated VE/VO2 during the second and third HI90 in comparison to E (P<0.05). The expected HR were higher during the MI70 exercise intensities regardless of group affiliation (P<0.05). The blood [La] response predicted time to exhaustion earlier than respiratory variables (P<0.05). Discussion: Blood lactate and acid/base fluctuations were not reflected by RER and the ventilatory equivalents. Furthermore, blood lactate is to prefer, in comparison to ventilatory variables, to study performance related recovery processes during endurance exercise with variations in intensity. The expected HR-VO2 relationship was not valid during VIP.
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| 2. |
- Björklund, Glenn, et al.
(författare)
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Performance predicting factors in prolonged exhausting exercise of varying intensity
- 2007
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 99:4, s. 423-429
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Tidskriftsartikel (refereegranskat)abstract
- Several endurance sports, e.g. road cycling, have a varying intensity profile during competition. At present, few laboratory tests take this intensity profile into consideration. Thus, the purpose of this study was to examine the prognostic value of heart rate (HR), lactate (La−1), potassium (K+), and respiratory exchange ratio (RER) performance at an exhausting cycling exercise with varying intensity. Eight national level cyclists performed two cycle tests each on a cycle ergometer: (1) a incremental test to establish VO2max, maximum power (W max), and lactate threshold (VO2LT), and (2) a variable intensity protocol (VIP). Exercise intensity for the VIP was based upon the VO2max obtained during the incremental test. The VIP consisted of six high intense (HI) workloads at 90% of VO2max for 3 min each, interspersed by five middle intense (MI) workloads at 70% of VO2max for 6 min each. VO2 and HR were continuously measured throughout the tests. Venous blood samples were taken before, during, and after the test. Increases in HR, La-, K+, and RER were observed when workload changed from MI to HI workload (P < 0.05). Potassium and RER decreased after transition from HI to MI workloads (P < 0.05). There was a negative correlation between time to exhaustion and decrease in La- concentration during the first MI (r = −0.714; P = 0.047). Furthermore, time to exhaustion correlated with VO2LT calculated from the ramp test (r = 0.738; P = 0.037). Our results suggest that the magnitude of decrease of La−1 between the first HI workload and the consecutive MI workload could predict performance during prolonged exercise with variable intensity
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| 4. |
- de Bruijn, Robert, et al.
(författare)
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High hemoglobin levels in divers may be a result of apnea induced EPO-production
- 2005
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Ingår i: FASEB JOURNAL. ; , s. A211-A212
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Konferensbidrag (refereegranskat)abstract
- Oxygen storage capacity is important for apneic duration and affects performance in endurance sports. We studied if hemoglobin concentration (Hb) was different in divers compared to endurance athletes and untrained subjects and if any differences could be connected to training-induced erythropoietin (EPO) -production. We first compared Hb in 3 groups of subjects: 13 elite apneic divers (35±4 years), 13 elite cross-country skiers (20±1 years) and 23 untrained subjects (29±1 years) with similar weight and height. After 20 min of horizontal rest blood samples were drawn and analysed for Hb using standard methods. In a second experiment, we compared EPO levels before and after a series of 15 maximal apneas in air in 9 previously untrained volunteers (302 years). Apneas were spaced by 2 minutes, the last minute with hyperventilation to produce durations long enough to induce hypoxia. Values were also compared to the EPO levels of a control day without apneas. The apneic divers had higher Hb than untrained subjects (P<0.05) and skiers (P<0.01). After apnea training in untrained subjects EPO levels increased in all subjects, with a mean peak value after 3 h, where the increase was 135 % of the pre apnea value (P<0.05). No increase was observed during the same time period of the control day. We concluded that higher Hb levels in apneic divers may be a result of enhanced EPO-production due to the apnea training.
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| 5. |
- Holmberg, Hans-Christer, et al.
(författare)
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Contribution of the legs to double-poling performance in elite cross-country skiers.
- 2006
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Ingår i: Medicine and science in sports and exercise. - : Ovid Technologies (Wolters Kluwer Health). - 0195-9131 .- 1530-0315. ; 38:10, s. 1853-60
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Tidskriftsartikel (refereegranskat)abstract
- In the classical style of cross-country skiing, the double-poling (DP) technique, which is regarded as an upper-body exercise, is used on the flatter parts of a course. Limited biomechanical and physiological data are available about DP compared with other cross-country skiing techniques. The purpose of the present study was to evaluate the possible role of the lower body during DP.Eleven elite cross-country skiers performed two incremental tests using DP roller skiing at 1 degree inclination on a treadmill with or without locking the knee and ankle joints (DPLOCKED and DPFREE). Maximal and peak oxygen uptake (VO2max and VO2peak) during classic diagonal skiing and DP, respectively, were measured. In addition, heart rate, blood lactate concentration, and maximal DP velocity (Vmax) were determined. Pole-ground reaction forces and joint angles (elbow, hip, knee, and ankle) were analyzed.The skiers obtained 7.7% higher VO2peak, 9.4% higher Vmax, and 11.7% longer time to exhaustion during DPFREE compared with DPLOCKED (all P < 0.05). There was a higher heart rate and blood lactate concentration in DPLOCKED at submaximal stages (all P < 0.05), with no difference in oxygen consumption. At 85% Vmax, corresponding to approximately 81% VO2peak FREE, the differences in physiological variables were accompanied by a 13.6% higher poling frequency, a 4.9% shorter poling phase, 13.3% shorter recovery phase, and 10.9% lower relative pole force in DPLOCKED (all P < 0.05).Movements of the knee and ankle joints are an integrative part in the skillful use of the DP technique, and restriction of the motion in these joints markedly affects both biomechanical and physiological variables, impairing DP performance.
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| 9. |
- Richardson, Matthew, et al.
(författare)
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Increase of hemoglobin concentration after maximal apneas in divers, skiers and untrained humans
- 2005
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Ingår i: Canadian Journal of Applied Physiology. - 1066-7814. ; 30:3, s. 276-281
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Tidskriftsartikel (refereegranskat)abstract
- Apnea is physiologically stressful and can within a short time frame pose a threat to survival. To sustain prolonged apnea, oxygen use should be minimized and its storage maximized. Two mechanisms known to have this effect are the cardiovascular diving response, directing the available oxygen selectively to the heart and brain, and spleen contraction increasing the circulating erythrocyte volume and thereby gas storage capacity. Spleen contraction is also observed after maximal exercise, and is thought to enhance aerobic performance. While the cardiovascular diving response is known to be more pronounced after apnea training, spleen contraction has not been studied in conjunction with apnea training or other types of training. The aim of the present investigation is to study the hematological responses to apnea performed during rest by elite apneic divers, by elite cross-country skiers and by untrained subjects. After 20 min of rest, subjects performed 3 maximal apneas spaced by 2 min normal breathing intervals. Blood samples were drawn before, directly after, and 10 min after the apnea series and hemoglobin concentration was measured. All groups responded to maximal apneas with an increase in hemoglobin concentration, which had disappeared after 10 min of recovery. The increase in hemoglobin concentration was more pronounced in the apneic divers (4g/L) than in skiers (3g/L) and untrained subjects (2g/L; P < 0.05). All groups prolonged their apneic times through the series, but the increase was most evident for the divers versus both the skiers (P < 0.05) and untrained subjects (P < 0.01). The results suggest that these responses could be more pronounced as a result of apnea training.
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| 10. |
- Richardson, Matthew, et al.
(författare)
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Increase of hemoglobin concentration after maximal apneas in divers, skiers and untrained humans
- 2005
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Ingår i: Canadian Journal of Applied Physiology. - : Canadian Science Publishing. - 1066-7814 .- 1543-2718. ; 30:3, s. 276-281
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Tidskriftsartikel (refereegranskat)abstract
- Human splenic contraction occurs both during apnea and maximal exercise, increasing the circulating erythrocyte volume. We investigated the hematological responses to 3 maximal apneas performed by elite apneic divers, elite cross-country skiers, and untrained subjects. Post-apnea hemoglobin concentration had increased in all groups, but especially in divers. The increases disappeared within 10 min of recovery. Apneic duration across apneas also increased the most in divers. Responses in divers could be more pronounced as a result of apnea training. Key words: breath hold, serial apneas, spleen contraction, cross-country skiing
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