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Performance predicting factors in prolonged exhausting exercise of varying intensity
Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. (Nationellt Vintersportcentrum / Swedish Winter Sports Research Centre)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. (Nationellt Vintersportcentrum / Swedish Winter Sports Research Centre)
Responsible organisation
2007 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 99, no 4, 423-429 p.Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
2007. Vol. 99, no 4, 423-429 p.
Keyword [en]
Cycling, Exercise, Lactate, Potassium
Keyword [sv]
Idrottsvetenskap
National Category
Sport and Fitness Sciences Microbiology
Identifiers
URN: urn:nbn:se:miun:diva-4539DOI: 10.1007/s00421-006-0352-0ISI: 000243963000011Scopus ID: 2-s2.0-33846872580Local ID: 5629OAI: oai:DiVA.org:miun-4539DiVA: diva2:29571
Note

VR-Medicine, External

Available from: 2008-09-30 Created: 2009-06-07 Last updated: 2016-10-04Bibliographically approved
In thesis
1. Metabolic and Cardiovascular Responses During Variable Intensity Exercise
Open this publication in new window or tab >>Metabolic and Cardiovascular Responses During Variable Intensity Exercise
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Previous research investigating endurance sports from a physiological perspectivehas mainly used constant or graded exercise protocols, although the nature ofsports like cross-country skiing and road cycling leads to continuous variations inworkload. Current knowledge is thus limited as regards physiological responses tovariations in exercise intensity. Therefore, the overall objective of the present thesiswas to investigate cardiovascular and metabolic responses to fluctuations inexercise intensity during exercise. The thesis is based on four studies (Studies I-IV);the first two studies use a variable intensity protocol with cardiorespiratory andblood measurements during cycling (Study I) and diagonal skiing (Study II). InStudy III one-legged exercise was used to investigate muscle blood flow duringvariable intensity exercise using PET scanning, and Study IV was performed toinvestigate the transition from high to low exercise intensity in diagonal skiing,with both physiological and biomechanical measurements. The current thesisdemonstrates that the reduction in blood lactate concentration after high-intensityworkloads is an important performance characteristic of prolonged variableintensity exercise while cycling and diagonal skiing (Studies I-II). Furthermore,during diagonal skiing, superior blood lactate recovery was associated with a highaerobic power (VO2max) (Study II). Respiratory variables such as VE/VO2, VE/VCO2and RER recovered independently of VO2max and did not reflect the blood lactate oracid base levels during variable intensity exercise during either cycling or diagonalskiing (Studies I-II). There was an upward drift in HR over time, but not inpulmonary VO2, with variable intensity exercise during both prolonged cyclingand diagonal skiing. As a result, the linear HR-VO2 relationship that wasestablished with a graded protocol was not present during variable intensityexercise (Studies I-II). In Study III, blood flow heterogeneity during one-leggedexercise increased when the exercise intensity decreased, but remained unchangedbetween the high intensity workloads. Furthermore, there was an excessiveincrease in muscular VO2 in the consecutive high-intensity workloads, mainlyexplained by increased O2 extraction, as O2 delivery and blood flow remainedunchanged. In diagonal skiing (Study IV) the arms had a lower O2 extraction thanthe legs, which could partly be explained by their longer contact phase along withmuch higher muscle activation. Furthermore, in Study IV, the O2 extraction in botharms and legs was at the upper limit during the high intensity workload with nofurther margin for increase. This could explain why no excessive increase inpulmonary VO2 occurred during diagonal skiing (Study II), as increased O2extraction is suggested to be the main reason for this excessive increase in VO2(Study III).

Place, publisher, year, edition, pages
Sundsvall: Mittuniversitetet, 2010
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 86
Keyword
cross-country skiing, cycling, heart rate, lactate, O2 extraction, O2 uptake, performance, ventilation
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-11744 (URN)978-91-86073-76-3 (ISBN)
Public defence
2010-06-16, Q221, Östersund, 10:30 (English)
Available from: 2010-07-01 Created: 2010-06-21 Last updated: 2013-11-21Bibliographically approved

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