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It seems sensible to establish that TTE in laboratories for each cyclist and for each specific physiologic event, involves a very high cost in human resources, time, and materials, as well as been highly demanding for cyclists from the physiological and physiological point of view. These facts preclude its widespread use for most of them. However, it is also evident that although the use of potentiometers in the field and the analysis of power profiles based on specific times represent the future, it must be recognized that, without the basic research carried out in laboratories around the world during the last three decades, this future would lack of the sufficient scientific support.

[Resumen]: En la última década han aparecido una serie de estudios que han demostrado que la fatiga mental puede afectar no sólo al rendimiento cognitivo si no también al rendimiento físico. A pesar de que actualmente, no existe un consenso entre los diferentes tipos de pruebas de rendimiento en resistencia de los estudios, los resultados obtenidos parecen apuntar que las tareas mentalmente fatigosas tienen un efecto negativo sobre el rendimiento., [Abstract]: In the last decade, a series of studies have appeared that have shown that mental fatigue can affect not only cognitive performance but also physical performance. Although there is currently no consensus between the different types of endurance performance tests in the studies, the results obtained seem to indicate that mentally fatiguing tasks have a negative effect on performance.

It seems sensible to establish that TTE in laboratories for each cyclist and for each specific physiologic event, involves a very high cost in human resources, time, and materials, as well as been highly demanding for cyclists from the physiological and physiological point of view. These facts preclude its widespread use for most of them. However, it is also evident that although the use of potentiometers in the field and the analysis of power profiles based on specific times represent the future, it must be recognized that, without the basic research carried out in laboratories around the world during the last three decades, this future would lack of the sufficient scientific support.

The use of nicotine administered through smokeless tobacco (snus) has increased among athletes. The purpose of this study was to investigate the ergogenic effects of snus on aerobic performance during exercise until exhaustion in athletes after abstinence or satiety nicotine conditions. The study utilized a randomized, controlled, within-subject design experiment. Sixteen male snus-user athletes completed an exercise until exhaustion at a constant load of their 80% of VO2max (calculated by a maximal incremental test) in two separate sessions, corresponding to nicotine conditions: 12-hour overnight abstinence and satiety. A portion of 1 g of snus (similar to 8 mg/g of nicotine) was administered 25 minutes before each experimental test. In each session, time to exhaustion (TTE), global rating of perceived exertion, cardiovascular and metabolic responses, and muscle and cerebral oxygenation were measured. Nicotine and cotinine analysis confirmed session conditions (abstinence or satiety). Snus induced a significant increase (+13.1%) of TTE following abstinence (24.1 +/- 10.7 minutes) compared to satiety condition (20.9 +/- 8.0 minutes; P = 0.0131). The baseline values revealed that abstinence of snus induced significant increase in the oxygenation of the muscular tissues (+4%), in metabolic values and in cardiovascular parameters, when compared to satiety condition. Our results indicate an increase of exercise performance (+13.1% TTE) due to snus administration in an abstinence condition. Considering that twelve hours of abstinence from snus-contained nicotine affected metabolic, cardiovascular and muscular tissue oxygenation, we suggest that snus administration at test time might relieve these withdrawal changes and yield an increase in time to exhaustion.

Background: Smokeless tobacco is widely used by athletes to enhance performance. Nicotine is a central nervous system stimulant and acts on cardiocirculatory and metabolic systems, involving tissue blood flow and circulatory vasoreactivity. The aim of this study was to investigate the effects of the oral smokeless tobacco (Swedish snus (SS)) on the perception of fatigue and time to exhaustion (TTE) during moderate -intensity aerobic exercise.Methods: Fourteen healthy non-tobacco male users were recruited for a double-blind, controlled crossover design (SS vs. snus placebo (SP)). Subjects were tested for 3 sessions: experimental session 1 (Expl) consisted of an incremental test to determine the maximal aerobic power output (W-max), whereas Exp2 and Exp3 consisted of exercising at 65%W-max until exhaustion in SS or SP conditions. During Exp2 and Exp3, muscle and cerebral oxygenation was assessed by means of near-infrared spectroscopy, and the rating of perceived exertion (RPE) was recorded.Results: Comparing SS with SP tests, significant differences (p < 0.05) were found in the values of cerebral (similar to 3%) and muscular tissues oxygenation (similar to 4%) in the first 30 min of exercise. The RPE values were not significantly different between the 2 conditions (SS vs. SP). No significant difference was found in TTE (SS: 54.25 +/- 21.84 min; SP: 50.01 +/- 17.03 min).Conclusion: This study showed that muscular and cerebral oxygenation increased significantly with snus administration during an endurance exercise until exhaustion, but this did not affect fatigue perception and TTE. The results showed that snus could not be considered an ergogenic substance in non-tobacco users. (C) 2018 Published by Elsevier B.V. on behalf of Shanghai University of Sport. This is an open access article under the CC BY-NC-ND license.

Caffeine can stimulate the central nervous system and thus increase exercise tolerance throughout rating perceived exertion (RPE) changes and it can change the pace strategy (PS) during a physical task. The aim of this study was to check if caffeine supplementation might promote changes in PS during a laboratory run test (LRT). In a double-blind, crossover, randomized and counterbalanced fashion, fifteen healthy-male (age: 24 ± 4.4 years; VO2max. 53 ± 5 ml.Kg-1.min-1) ingested 6 mg•kg-1 of CAF or placebo supplementation, 60 minutes before the LRT. The LRT was three-minutes sets (at fixed speed, 1 km/h above Onset Blood Lactate Accumulation) until volitional exhaustion; Rest Time Interval (RTI) between sets were chosen by the participants in the first test (ranging from 30 to 60s). RPE, Heart Rate (HR) and blood plasma lactate concentration ([La]p) were collected at rest, immediately after each set and at the end of test. Time to exhaustion was higher for CAF (p= 0.014). RTI between sets was significantly lower in caffeine (p= 0.048) and this decreased significantly the time to perform a same distance (p= 0.034). Overall HR and [La]p was similar for both conditions (p= 0.252, p= 0.129, respectively). Despite similar overall RPE throughout test (p= 0.380), in caffeine, there was not a RPE abrupt increase similar to placebo. Caffeine supplementation can positively influence running PS (to decrease the RTI required for recovery between moments of high-intensity exercise), as well as, can make an individual run further (in the same event)., A cafeína pode estimular o sistema nervoso central e aumentar a tolerância ao exercício por meio de mudanças na percepção subjetiva de esforço (PSE), isso pode mudar a estratégia de ritmo (ER) durante uma corrida. Nosso objetivo foi verificar se a suplementação de cafeína promove mudanças na ER durante um teste de corrida de laboratório (TCL). De modo duplo-cego, cruzado, randomizado e contrabalançado, quinze homens saudáveis (idade: 24 ± 4,4 anos, VO2max. 53 ± 5 ml.Kg-1.min-1) ingeriram 6 mg/kg-1 de cafeína ou placebo, 60 minutos antes do TCL. O TCL consistiu de séries de três minutos (velocidade fixada à 1 km/h acima do “Onset Blood Lactate Accumulation”) até fadiga volicional; O Intervalo de Tempo de Descanso (ITD) entre as séries foi escolhido pelos participantes no primeiro teste (entre 30 a 60s). PSE, frequência cardíaca (FC) e lactato ([La]p) foram coletados em repouso, imediatamente após cada série e ao final do teste. O tempo de exaustão foi maior na situação cafeína (p= 0,014); o ITD foi significativamente menor na situação cafeína (p= 0,048), isso fez diminuir significativamente o tempo para realizar uma mesma distância (p= 0,034). A FC e [La]p foram semelhantes para ambas as condições (p= 0,252, p= 0,129, respectivamente). Apesar da semelhança da PSE ao longo do teste (p= 0,380), na situação cafeína não houve um aumento abrupto ao longo do teste como ocorreu na situação placebo. A suplementação de cafeína pode influenciar positivamente a ER durante uma corrida, além de aumentar a capacidade de correr mais (no mesmo evento).

Endurance athletes integrate four conditioning concepts in their training programs: high-volume training (HVT), "threshold-training" (THR), high-intensity interval training (HIIT) and a combination of these aforementioned concepts known as polarized training (POL). The purpose of this study was to explore which of these four training concepts provides the greatest response on key components of endurance performance in well-trained endurance athletes. Methods: Forty eight runners, cyclists, triathletes, and cross-country skiers (peak oxygen uptake: (VO2peak): 62.6 ± 7.1 mL·min-1·kg-1) were randomly assigned to one of four groups performing over 9 weeks. An incremental test, work economy and a VO2peak tests were performed. Training intensity was heart rate controlled. Results: POL demonstrated the greatest increase in VO2peak (+6.8 ml·min·kg-1 or 11.7%, P < 0.001), time to exhaustion during the ramp protocol (+17.4%, P < 0.001) and peak velocity/power (+5.1%, P < 0.01). Velocity/power at 4 mmol·L-1 increased after POL (+8.1%, P < 0.01) and HIIT (+5.6%, P < 0.05). No differences in pre- to post-changes of work economy were found between the groups. Body mass was reduced by 3.7% (P < 0.001) following HIIT, with no changes in the other groups. With the exception of slight improvements in work economy in THR, both HVT and THR had no further effects on measured variables of endurance performance (P > 0.05). Conclusion: POL resulted in the greatest improvements in most key variables of endurance performance in well-trained endurance athletes. THR or HVT did not lead to further improvements in performance related variables. © 2014 Stöggl and Sperlich., Correspondence Address: Stöggl, T.; Department of Sport Science and Kinesiology, University of Salzburg, Schlossallee 49, 5400 Hallein/Rif, Salzburg, Austria; email: thomas.stoeggl@sbg.ac.at

Endurance athletes integrate four conditioning concepts in their training programs: high-volume training (HVT), "threshold-training" (THR), high-intensity interval training (HIIT) and a combination of these aforementioned concepts known as polarized training (POL). The purpose of this study was to explore which of these four training concepts provides the greatest response on key components of endurance performance in well-trained endurance athletes. Methods: Forty eight runners, cyclists, triathletes, and cross-country skiers (peak oxygen uptake: (VO2peak): 62.6 ± 7.1 mL·min-1·kg-1) were randomly assigned to one of four groups performing over 9 weeks. An incremental test, work economy and a VO2peak tests were performed. Training intensity was heart rate controlled. Results: POL demonstrated the greatest increase in VO2peak (+6.8 ml·min·kg-1 or 11.7%, P < 0.001), time to exhaustion during the ramp protocol (+17.4%, P < 0.001) and peak velocity/power (+5.1%, P < 0.01). Velocity/power at 4 mmol·L-1 increased after POL (+8.1%, P < 0.01) and HIIT (+5.6%, P < 0.05). No differences in pre- to post-changes of work economy were found between the groups. Body mass was reduced by 3.7% (P < 0.001) following HIIT, with no changes in the other groups. With the exception of slight improvements in work economy in THR, both HVT and THR had no further effects on measured variables of endurance performance (P > 0.05). Conclusion: POL resulted in the greatest improvements in most key variables of endurance performance in well-trained endurance athletes. THR or HVT did not lead to further improvements in performance related variables. © 2014 Stöggl and Sperlich., Correspondence Address: Stöggl, T.; Department of Sport Science and Kinesiology, University of Salzburg, Schlossallee 49, 5400 Hallein/Rif, Salzburg, Austria; email: thomas.stoeggl@sbg.ac.at

Endurance athletes integrate four conditioning concepts in their training programs: high-volume training (HVT), "threshold-training" (THR), high-intensity interval training (HIIT) and a combination of these aforementioned concepts known as polarized training (POL). The purpose of this study was to explore which of these four training concepts provides the greatest response on key components of endurance performance in well-trained endurance athletes. Methods: Forty eight runners, cyclists, triathletes, and cross-country skiers (peak oxygen uptake: (VO2peak): 62.6 ± 7.1 mL·min-1·kg-1) were randomly assigned to one of four groups performing over 9 weeks. An incremental test, work economy and a VO2peak tests were performed. Training intensity was heart rate controlled. Results: POL demonstrated the greatest increase in VO2peak (+6.8 ml·min·kg-1 or 11.7%, P < 0.001), time to exhaustion during the ramp protocol (+17.4%, P < 0.001) and peak velocity/power (+5.1%, P < 0.01). Velocity/power at 4 mmol·L-1 increased after POL (+8.1%, P < 0.01) and HIIT (+5.6%, P < 0.05). No differences in pre- to post-changes of work economy were found between the groups. Body mass was reduced by 3.7% (P < 0.001) following HIIT, with no changes in the other groups. With the exception of slight improvements in work economy in THR, both HVT and THR had no further effects on measured variables of endurance performance (P > 0.05). Conclusion: POL resulted in the greatest improvements in most key variables of endurance performance in well-trained endurance athletes. THR or HVT did not lead to further improvements in performance related variables. © 2014 Stöggl and Sperlich., Correspondence Address: Stöggl, T.; Department of Sport Science and Kinesiology, University of Salzburg, Schlossallee 49, 5400 Hallein/Rif, Salzburg, Austria; email: thomas.stoeggl@sbg.ac.at

Endurance athletes integrate four conditioning concepts in their training programs: high-volume training (HVT), "threshold-training" (THR), high-intensity interval training (HIIT) and a combination of these aforementioned concepts known as polarized training (POL). The purpose of this study was to explore which of these four training concepts provides the greatest response on key components of endurance performance in well-trained endurance athletes. Methods: Forty eight runners, cyclists, triathletes, and cross-country skiers (peak oxygen uptake: (VO2peak): 62.6 ± 7.1 mL·min-1·kg-1) were randomly assigned to one of four groups performing over 9 weeks. An incremental test, work economy and a VO2peak tests were performed. Training intensity was heart rate controlled. Results: POL demonstrated the greatest increase in VO2peak (+6.8 ml·min·kg-1 or 11.7%, P < 0.001), time to exhaustion during the ramp protocol (+17.4%, P < 0.001) and peak velocity/power (+5.1%, P < 0.01). Velocity/power at 4 mmol·L-1 increased after POL (+8.1%, P < 0.01) and HIIT (+5.6%, P < 0.05). No differences in pre- to post-changes of work economy were found between the groups. Body mass was reduced by 3.7% (P < 0.001) following HIIT, with no changes in the other groups. With the exception of slight improvements in work economy in THR, both HVT and THR had no further effects on measured variables of endurance performance (P > 0.05). Conclusion: POL resulted in the greatest improvements in most key variables of endurance performance in well-trained endurance athletes. THR or HVT did not lead to further improvements in performance related variables. © 2014 Stöggl and Sperlich., Correspondence Address: Stöggl, T.; Department of Sport Science and Kinesiology, University of Salzburg, Schlossallee 49, 5400 Hallein/Rif, Salzburg, Austria; email: thomas.stoeggl@sbg.ac.at

Endurance athletes integrate four conditioning concepts in their training programs: high-volume training (HVT), "threshold-training" (THR), high-intensity interval training (HIIT) and a combination of these aforementioned concepts known as polarized training (POL). The purpose of this study was to explore which of these four training concepts provides the greatest response on key components of endurance performance in well-trained endurance athletes. Methods: Forty eight runners, cyclists, triathletes, and cross-country skiers (peak oxygen uptake: (VO2peak): 62.6 ± 7.1 mL·min-1·kg-1) were randomly assigned to one of four groups performing over 9 weeks. An incremental test, work economy and a VO2peak tests were performed. Training intensity was heart rate controlled. Results: POL demonstrated the greatest increase in VO2peak (+6.8 ml·min·kg-1 or 11.7%, P < 0.001), time to exhaustion during the ramp protocol (+17.4%, P < 0.001) and peak velocity/power (+5.1%, P < 0.01). Velocity/power at 4 mmol·L-1 increased after POL (+8.1%, P < 0.01) and HIIT (+5.6%, P < 0.05). No differences in pre- to post-changes of work economy were found between the groups. Body mass was reduced by 3.7% (P < 0.001) following HIIT, with no changes in the other groups. With the exception of slight improvements in work economy in THR, both HVT and THR had no further effects on measured variables of endurance performance (P > 0.05). Conclusion: POL resulted in the greatest improvements in most key variables of endurance performance in well-trained endurance athletes. THR or HVT did not lead to further improvements in performance related variables. © 2014 Stöggl and Sperlich., Correspondence Address: Stöggl, T.; Department of Sport Science and Kinesiology, University of Salzburg, Schlossallee 49, 5400 Hallein/Rif, Salzburg, Austria; email: thomas.stoeggl@sbg.ac.at

The aim of this thesis was to investigate roller ski characteristics; classical and freestyle roller skis’ rolling resistance coefficients (μR) and classical style roller skis’ static friction coefficients (μS), and to study the influence of different μR and μS on cross-country skiers’ performance and both physiological and biomechanical indices. The aim was also to study differences in skiing economy and efficiency between recreational skiers, female and male junior and senior elite cross-country skiers.The experiments showed that during a time period of 30 minutes of rolling on a treadmill (warm-up), μR decreased significantly (p<0.05) to about 60-65 % and 70-75 % of its initial value for freestyle and classical roller skis respectively. Also, there was a significant influence of normal force on μR, while different velocities and inclinations of the treadmill only resulted in small changes in μR.The study of the influence on physiological variables of a ~50 % change in μR showed that during submaximal steady rate exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non-significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a change in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non-significant or small.The study of classical style roller skis μS showed values that were five to eight times more than the values of μS reported from on-snow skiing with grip-waxed cross-country skis.The subsequent physiological and biomechanical experiments with different μS showed a significantly lower skiing economy (~14 % higher v̇O2), higher heart rate, lower propulsive forces coming from the legs and shorter time to exhaustion (~30 %) when using a different type of roller ski wi, Syftet med denna avhandling var att undersöka fristils- och klassiska rullskidors rullmotståndskoefficienter (μR) och klassiska rullskidors statiska friktionskoefficienter (μS) samt effekter av olika μR och μS på längdskidåkares prestation vid rullskidåkning på rullande band. Syftet var även att undersöka s.k. åkekonomi och mekanisk verkningsgrad mellan motionärer och kvinnliga och manliga junior- och seniorlängdskidåkare på elitnivå.Experimenten visade att under en period av 30 minuters kontinuerligt rullande, på rullande band, så sjönk μR signifikant (p<0.05) till 60-65 % och 70-75 % av initiala värden, för fristils- respektive klassiska rullskidor. Undersökandet av olika normalkrafter, hastigheter och lutningars påverkan på μR resulterade i en signifikant, negativ korrelation för μR som funktion av normalkraft, medan olika hastigheter och lutningar endast medförde små förändringar av μR.Studien som undersökte fysiologiska effekter av olika μR visade, vid submaximala konstanta arbetsbelastningar, att yttre effekt, syreupptagning, hjärtfrekvens och blodlaktat förändrades signifikant vid ~50 % förändring av μR. Försökspersonernas frekvens och sträcka per frekvens samt skattning av upplevd ansträngning resulterade dock i mestadels icke signifikanta eller små förändringar. Protokollen med successivt ökande arbetsbelastning (maxtest) resulterade i signifikant förändrad tid till utmattning, vid ~50 % förändring av μR. Detta inträffade utan signifikant skillnad i maximal syreupptagning, hjärtfrekvens och blodlaktat, vilket även mestadels gällde för skattning av upplevd ansträngning.Experimenten som undersökte klassiska rullskidors μS visade att dessa erhöll värden som är fem till åtta gånger högre än vad som rapporterats från studier av μS på snö med fästvallade skidor.Den efterföljande studien som undersökte fysiologiska och biomekaniska influenser av olika μS visade, vid submaximala konstanta arbetsbelastningar, att åkekonomin försämrades (~14 % högre syreförbruknin

The aim of this thesis was to investigate roller ski characteristics; classical and freestyle roller skis’ rolling resistance coefficients (μR) and classical style roller skis’ static friction coefficients (μS), and to study the influence of different μR and μS on cross-country skiers’ performance and both physiological and biomechanical indices. The aim was also to study differences in skiing economy and efficiency between recreational skiers, female and male junior and senior elite cross-country skiers.The experiments showed that during a time period of 30 minutes of rolling on a treadmill (warm-up), μR decreased significantly (p<0.05) to about 60-65 % and 70-75 % of its initial value for freestyle and classical roller skis respectively. Also, there was a significant influence of normal force on μR, while different velocities and inclinations of the treadmill only resulted in small changes in μR.The study of the influence on physiological variables of a ~50 % change in μR showed that during submaximal steady rate exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non-significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a change in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non-significant or small.The study of classical style roller skis μS showed values that were five to eight times more than the values of μS reported from on-snow skiing with grip-waxed cross-country skis.The subsequent physiological and biomechanical experiments with different μS showed a significantly lower skiing economy (~14 % higher v̇O2), higher heart rate, lower propulsive forces coming from the legs and shorter time to exhaustion (~30 %) when using a different type of roller ski wi, Syftet med denna avhandling var att undersöka fristils- och klassiska rullskidors rullmotståndskoefficienter (μR) och klassiska rullskidors statiska friktionskoefficienter (μS) samt effekter av olika μR och μS på längdskidåkares prestation vid rullskidåkning på rullande band. Syftet var även att undersöka s.k. åkekonomi och mekanisk verkningsgrad mellan motionärer och kvinnliga och manliga junior- och seniorlängdskidåkare på elitnivå.Experimenten visade att under en period av 30 minuters kontinuerligt rullande, på rullande band, så sjönk μR signifikant (p<0.05) till 60-65 % och 70-75 % av initiala värden, för fristils- respektive klassiska rullskidor. Undersökandet av olika normalkrafter, hastigheter och lutningars påverkan på μR resulterade i en signifikant, negativ korrelation för μR som funktion av normalkraft, medan olika hastigheter och lutningar endast medförde små förändringar av μR.Studien som undersökte fysiologiska effekter av olika μR visade, vid submaximala konstanta arbetsbelastningar, att yttre effekt, syreupptagning, hjärtfrekvens och blodlaktat förändrades signifikant vid ~50 % förändring av μR. Försökspersonernas frekvens och sträcka per frekvens samt skattning av upplevd ansträngning resulterade dock i mestadels icke signifikanta eller små förändringar. Protokollen med successivt ökande arbetsbelastning (maxtest) resulterade i signifikant förändrad tid till utmattning, vid ~50 % förändring av μR. Detta inträffade utan signifikant skillnad i maximal syreupptagning, hjärtfrekvens och blodlaktat, vilket även mestadels gällde för skattning av upplevd ansträngning.Experimenten som undersökte klassiska rullskidors μS visade att dessa erhöll värden som är fem till åtta gånger högre än vad som rapporterats från studier av μS på snö med fästvallade skidor.Den efterföljande studien som undersökte fysiologiska och biomekaniska influenser av olika μS visade, vid submaximala konstanta arbetsbelastningar, att åkekonomin försämrades (~14 % högre syreförbruknin

The aim of this thesis was to investigate roller ski characteristics; classical and freestyle roller skis’ rolling resistance coefficients (μR) and classical style roller skis’ static friction coefficients (μS), and to study the influence of different μR and μS on cross-country skiers’ performance and both physiological and biomechanical indices. The aim was also to study differences in skiing economy and efficiency between recreational skiers, female and male junior and senior elite cross-country skiers.The experiments showed that during a time period of 30 minutes of rolling on a treadmill (warm-up), μR decreased significantly (p<0.05) to about 60-65 % and 70-75 % of its initial value for freestyle and classical roller skis respectively. Also, there was a significant influence of normal force on μR, while different velocities and inclinations of the treadmill only resulted in small changes in μR.The study of the influence on physiological variables of a ~50 % change in μR showed that during submaximal steady rate exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non-significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a change in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non-significant or small.The study of classical style roller skis μS showed values that were five to eight times more than the values of μS reported from on-snow skiing with grip-waxed cross-country skis.The subsequent physiological and biomechanical experiments with different μS showed a significantly lower skiing economy (~14 % higher v̇O2), higher heart rate, lower propulsive forces coming from the legs and shorter time to exhaustion (~30 %) when using a different type of roller ski wi, Syftet med denna avhandling var att undersöka fristils- och klassiska rullskidors rullmotståndskoefficienter (μR) och klassiska rullskidors statiska friktionskoefficienter (μS) samt effekter av olika μR och μS på längdskidåkares prestation vid rullskidåkning på rullande band. Syftet var även att undersöka s.k. åkekonomi och mekanisk verkningsgrad mellan motionärer och kvinnliga och manliga junior- och seniorlängdskidåkare på elitnivå.Experimenten visade att under en period av 30 minuters kontinuerligt rullande, på rullande band, så sjönk μR signifikant (p<0.05) till 60-65 % och 70-75 % av initiala värden, för fristils- respektive klassiska rullskidor. Undersökandet av olika normalkrafter, hastigheter och lutningars påverkan på μR resulterade i en signifikant, negativ korrelation för μR som funktion av normalkraft, medan olika hastigheter och lutningar endast medförde små förändringar av μR.Studien som undersökte fysiologiska effekter av olika μR visade, vid submaximala konstanta arbetsbelastningar, att yttre effekt, syreupptagning, hjärtfrekvens och blodlaktat förändrades signifikant vid ~50 % förändring av μR. Försökspersonernas frekvens och sträcka per frekvens samt skattning av upplevd ansträngning resulterade dock i mestadels icke signifikanta eller små förändringar. Protokollen med successivt ökande arbetsbelastning (maxtest) resulterade i signifikant förändrad tid till utmattning, vid ~50 % förändring av μR. Detta inträffade utan signifikant skillnad i maximal syreupptagning, hjärtfrekvens och blodlaktat, vilket även mestadels gällde för skattning av upplevd ansträngning.Experimenten som undersökte klassiska rullskidors μS visade att dessa erhöll värden som är fem till åtta gånger högre än vad som rapporterats från studier av μS på snö med fästvallade skidor.Den efterföljande studien som undersökte fysiologiska och biomekaniska influenser av olika μS visade, vid submaximala konstanta arbetsbelastningar, att åkekonomin försämrades (~14 % högre syreförbruknin

Purpose: To investigate the effect of ice slurry ingestion on thermoregulatory responses and submaximal running time in the heat. Methods: On two separate occasions, in a counterbalanced order, 10 males ingested 7.5 g·kg-1 of either ice slurry (-1°C) or cold water (4°C) before running to exhaustion at their first ventilatory threshold in a hot environment (34.0°C ± 0.2°C, 54.9% ± 5.9% relative humidity). Rectal and skin temperatures, HR, sweating rate, and ratings of thermal sensation and perceived exertion were measured. Results: Running time was longer (P = 0.001) after ice slurry (50.2 ± 8.5 min) versus cold water (40.7 ± 7.2 min) ingestion. Before running, rectal temperature dropped 0.66°C ± 0.14°C after ice slurry ingestion compared with 0.25°C ± 0.09°C (P = 0.001) with cold water and remained lower for the first 30 min of exercise. At exhaustion, however, rectal temperature was higher (P = 0.001) with ice slurry (39.36°C ± 0.41°C) versus cold water ingestion (39.05°C ± 0.37°C). During exercise, mean skin temperature was similar between conditions (P = 0.992), as was HR (P = 0.122) and sweat rate (P = 0.242). After ice slurry ingestion, subjects stored more heat during exercise (100.10 ± 25.00 vs 78.93 ± 20.52 W·m-2, P = 0.005), and mean ratings of thermal sensation (P = 0.001) and perceived exertion (P = 0.022) were lower. Conclusions: Compared with cold water, ice slurry ingestion lowered preexercise rectal temperature, increased submaximal endurance running time in the heat (+19% ± 6%), and allowed rectal temperature to become higher at exhaustion. As such, ice slurry ingestion may be an effective and practical precooling maneuver for athletes competing in hot environments.

Purpose: To investigate the effect of ice slurry ingestion on thermoregulatory responses and submaximal running time in the heat. Methods: On two separate occasions, in a counterbalanced order, 10 males ingested 7.5 g·kg-1 of either ice slurry (-1°C) or cold water (4°C) before running to exhaustion at their first ventilatory threshold in a hot environment (34.0°C ± 0.2°C, 54.9% ± 5.9% relative humidity). Rectal and skin temperatures, HR, sweating rate, and ratings of thermal sensation and perceived exertion were measured. Results: Running time was longer (P = 0.001) after ice slurry (50.2 ± 8.5 min) versus cold water (40.7 ± 7.2 min) ingestion. Before running, rectal temperature dropped 0.66°C ± 0.14°C after ice slurry ingestion compared with 0.25°C ± 0.09°C (P = 0.001) with cold water and remained lower for the first 30 min of exercise. At exhaustion, however, rectal temperature was higher (P = 0.001) with ice slurry (39.36°C ± 0.41°C) versus cold water ingestion (39.05°C ± 0.37°C). During exercise, mean skin temperature was similar between conditions (P = 0.992), as was HR (P = 0.122) and sweat rate (P = 0.242). After ice slurry ingestion, subjects stored more heat during exercise (100.10 ± 25.00 vs 78.93 ± 20.52 W·m-2, P = 0.005), and mean ratings of thermal sensation (P = 0.001) and perceived exertion (P = 0.022) were lower. Conclusions: Compared with cold water, ice slurry ingestion lowered preexercise rectal temperature, increased submaximal endurance running time in the heat (+19% ± 6%), and allowed rectal temperature to become higher at exhaustion. As such, ice slurry ingestion may be an effective and practical precooling maneuver for athletes competing in hot environments.

The effects of three textiles with increasing compressive surface were compared with non-compressive conventional clothing on physiological and perceptual variables during sub-maximal and maximal running. 15 well-trained endurance athletes (mean ± s, age: 27.1 ± 4.8 years, VO2max 63.7 ± 4.9 ml∙min-1∙kg-1) performed four sub-maximal (~70%VO2max) and maximal tests with and without different compression stockings, tights, and whole body compression suits. Arterial lactate concentration, oxygen saturation and partial pressure, pH, oxygen uptake and ratings of muscle soreness were recorded before, during, and after all tests. Additionally, time to exhaustion was assessed. Sub-maximal (P = 0.22) and maximal oxygen uptake (P = 0.26), arterial lactate concentration (P = 0.16; 0.20), pH (P = 0.23; 0.46), oxygen saturation (P = 0.13; 0.26) and oxygen partial pressure (P = 0.09; 0.20) did not differ between the types of clothing (effect sizes = 0.00-0.45). Ratings of perceived exertion (P = 0.10; 0.15), muscle soreness (P = 0.09; 0.10) and time to exhaustion (P = 0.16) were also unaffected by the different clothing (effect sizes = 0.28-0.85). For the first time, the effect on endurance performance of different types of compression clothing with increasing amount of compressive surface was evaluated. Overall, there were no performance benefits when using the compression garments., Integrative Physiologi & Biomechanics, Integrative Human Physiology

Modern ski-treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical fitness in a laboratory environment whilst performing classical and freestyle (skating) techniques on roller skis. For elite athletes the differences in performance between test occasions are quite small, thus emphasising the importance of knowing the roller skis’ rolling resistance in order to allow the correct comparison between the results of different test occasions. In this study the roller skis’ rolling resistance has been measured using equipment on the ski-treadmill. The study investigates the influence of significant changes in rolling resistance on physiological variables. The results show that during submaximal exercise, heart rate, blood lactate, power and oxygen uptake are significantly changed by different rolling resistances, while there are no significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests show that time to exhaustion is significantly changed by different rolling resistances and this occurred without significant changes in maximal oxygen uptake and heart rate, and the influence on maximal power and ratings of perceived exertion were insignificant or small., Sportstech

The purpose of the study was to identify critical power (CP) in boys and girls and to examine the physiological responses to exercise at and 10% above CP (CP+10%) in a sub-group of boys. Nine boys and 9 girls (mean age 12.3 (0.5) y performed 3 constant-load tests to derive CP. Eight of the boys then exercised, in random order, at CP and CP+10% until volitional exhaustion. CP was 123 (28) and 91 (26) W for boys and girls, respectively (p < 0.02), which was equivalent to 75 (6) and 72 (10) % of peak oxygen uptake, respectively (p > 0.47). Boys' time to exhaustion at CP was 18 min 37 s (4 min 13 s), which was significantly longer (p < 0.007) than that at CP+10% (9 min 42 s (2 min 31 s)). End-exercise values for blood lactate concentration (B[La]) and maximal oxygen uptake were higher in the CP+10% trial (5.0 (2.4) mmol·L-1 and 2.15 (0.4) L·min-1, respectively) than in the CP trial, (B[La], 4.7 (2.1) mmol·L-1; maximal oxygen uptake, 2.05 (0.35) L·min-1; p > 0.13). Peak oxygen uptake (expressed as a percentage of the peak value) was not attained at the end of the trials (94 (12) and 98 (14) % for CP and CP+10%, respectively). These results provide information about the boundary between the heavy and severe exercise intensity domains in children, and have demonstrated that CP in a group of boys does not represent a sustainable steady-state intensity of exercise., Le but de cette étude est de déterminer la puissance critique (CP) des filles et des garçons et d'analyser chez un sous-groupe de garçons les ajustements physiologiques à cette intensité de travail et à 10 % au-dessus de cette valeur (CP+10 %). Neuf filles et neuf garçons âgés de 12,3 (0,5) ans participent à trois épreuves de charge constante conçues pour l'évaluation de la CP. Ensuite, huit garçons participent de façon aléatoire à un effort d'intensité équivalant à la CP et à la CP+10 % jusqu'à l'épuisement volontaire. La CP des garçons est de 123 (28) W et celle des filles est de 91 (26) W (p < 0,02), ce qui équivaut respectivement à 75 (6) % et 72 (10) % du consommation d'oxygene de pointe (p > 0,47). Le temps de performance jusqu'à l'épuisement à une intensité correspondant à la CP est de 18 min 37 s (4 min 13 s), ce qui est significativement plus long (p < 0,007) que le temps de performance (9 min 42 s (2 min 31 s)) à une intensité correspondant à la CP+10 %. Les valeurs de la concentration de lactate sanguin (B[la]) et du consommation d'oxygene sont supérieures à la fin de l'effort réalisé à la CP+10 % (B[la], 5,0 (2,4) mmol·L-1 et consommation d'oxygene, 2,15 (0,4) L·min-1) qu'à l'effort réalisé à la CP (B[la], 4,7 (2,1) mmol·L-1 et consommation d'oxygene, 2,05 (0,35) L·min-1, p > 0,13). À la fin des épreuves, les sujets n'atteignent pas le consommation d'oxygene de pointe (exprimé en pourcentage de la valeur de pointe), soit 94 (12) % et 98 (14) % aux puissances respectives de CP et de CP+10 %. Ces observations constituent des balises entre l'effort intense et l'effort excessif chez les enfants. De plus, un effort mené à la CP chez un groupe de garçons ne correspond pas à une intensité d'exercice qui puisse être maintenue en régime stable.

This study investigates whether a 6-wk intermittent hypoxia training (IHT), designed to avoid reductions in training loads and intensities, improves the endurance performance capacity of competitive distance runners. Eighteen athletes were randomly assigned to train in normoxia [Nor group; n = 9; maximal oxygen uptake (VO2 max) = 61.5 +/- 1.1 ml x kg(-1) x min(-1)] or intermittently in hypoxia (Hyp group; n = 9; VO2 max = 64.2 +/- 1.2 ml x kg(-1) x min(-1)). Into their usual normoxic training schedule, athletes included two weekly high-intensity (second ventilatory threshold) and moderate-duration (24-40 min) training sessions, performed either in normoxia [inspired O2 fraction (FiO2) = 20.9%] or in normobaric hypoxia (FiO2) = 14.5%). Before and after training, all athletes realized 1) a normoxic and hypoxic incremental test to determine VO2 max and ventilatory thresholds (first and second ventilatory threshold), and 2) an all-out test at the pretraining minimal velocity eliciting VO2 max to determine their time to exhaustion (T(lim)) and the parameters of O2 uptake (VO2) kinetics. Only the Hyp group significantly improved VO2 max (+5% at both FiO2, P < 0.05), without changes in blood O2-carrying capacity. Moreover, T(lim) lengthened in the Hyp group only (+35%, P < 0.001), without significant modifications of VO2 kinetics. Despite similar training load, the Nor group displayed no such improvements, with unchanged VO2 max (+1%, nonsignificant), T(lim) (+10%, nonsignificant), and VO2 kinetics. In addition, T(lim) improvements in the Hyp group were not correlated with concomitant modifications of other parameters, including VO2 max or VO2 kinetics. The present IHT model, involving specific high-intensity and moderate-duration hypoxic sessions, may potentialize the metabolic stimuli of training in already trained athletes and elicit peripheral muscle adaptations, resulting in increased endurance performance capacity.

This study investigates whether adaptations of mitochondrial function accompany the improvement of endurance performance capacity observed in well-trained athletes after an intermittent hypoxic training program. Fifteen endurance-trained athletes performed two weekly training sessions on treadmill at the velocity associated with the second ventilatory threshold (VT2) with inspired O2 fraction = 14.5% [hypoxic group (Hyp), n = 8] or with inspired O2 fraction = 21% [normoxic group (Nor), n = 7], integrated into their usual training, for 6 wk. Before and after training, oxygen uptake (VO2) and speed at VT2, maximal VO2 (VO2 max), and time to exhaustion at velocity of VO2 max (minimal speed associated with VO2 max) were measured, and muscle biopsies of vastus lateralis were harvested. Muscle oxidative capacities and sensitivity of mitochondrial respiration to ADP (Km) were evaluated on permeabilized muscle fibers. Time to exhaustion, VO2 at VT2, and VO2 max were significantly improved in Hyp (+42, +8, and +5%, respectively) but not in Nor. No increase in muscle oxidative capacity was obtained with either training protocol. However, mitochondrial regulation shifted to a more oxidative profile in Hyp only as shown by the increased Km for ADP (Nor: before 476 +/- 63, after 524 +/- 62 microM, not significant; Hyp: before 441 +/- 59, after 694 +/- 51 microM, P < 0.05). Thus including hypoxia sessions into the usual training of athletes qualitatively ameliorates mitochondrial function by increasing the respiratory control by creatine, providing a tighter integration between ATP demand and supply.

Due to more stringent requirements to protect personnel against hazardous gasses, the inspiratory resistance of the present generation of respiratory protective devices tends to increase. Therefore an important question is to what extent inspiratory resistance may increase without giving problems during physical work. In this study the effects of three levels (0.24; 1.4 and 8.3 kPasl-1) of inspiratory resistance were tested on maximal voluntary performance. Nine male subjects performed a graded exercise test on a cycle ergometer with and without these three levels of inspiratory resistance. Oxygen consumption, heart rate, time to exhaustion and external work were measured. The results of these experiments showed that increasing inspiratory resistance led to a reduction of time to exhaustion (TTE) on a graded exercise test(GXT). Without inspiratory resistance the mean TTE was 11.9 min, the three levels of resistance gave the following mean TTE's: 10.7, 7.8 and 2.7 min. This study showed that TTE on a GXT can be predicted when physical fitness (VO 2-max) of the subject and inspiratory resistance are known. The metabolic rate of the subjects was higher with inspiratory resistance, but no differences were found between the three selected inspiratory loads. Other breathing parameters as minute ventilation, tidal volume, expiration time and breathing frequency showed no or minor differences between the inspiratory resistances. The most important conclusion of these experiments is that the overall workload increases due to an increase in inspiratory resistance