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- Andersson, Erik, et al.
(författare)
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Analysis of sprint cross-country skiing using a differential global navigation satellite system
- 2010
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 110:3, s. 585-595
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Tidskriftsartikel (refereegranskat)abstract
- The purpose was to examine skiing velocities, gear choice (G2-7) and cycle rates during a skating sprint time trial (STT) and their relationships to performance, as well as to examine relationships between aerobic power, body composition and maximal skiing velocity versus STT performance. Nine male elite cross-country skiers performed three tests on snow: (1) Maximum velocity test (Vmax) performed using G3 skating, (2) Vmax test performed using double poling (DP) technique and (3) a STT over 1,425 m. Additional measurements of VO2max during roller skiing and body composition using iDXA were made. Differential global navigation satellite system data were used for position and velocity and synchronized with video during STT. The STT encompassed a large velocity range (2.9-12.9 m s-1) and multiple transitions (21-34) between skiing gears. Skiing velocity in the uphill sections was related to gear selection between G2 and G3. STT performance was most strongly correlated to uphill time (r = 0.92, P < 0.05), the percentage use of G2 (r = -0.72, P < 0.05), and DP Vmax (r = -0.71, P < 0.05). The velocity decrease in the uphills from lap 1 to lap 2 was correlated with VO2max (r = -0.78, P < 0.05). Vmax in DP and G3 were related to percent of racing time using G3. In conclusion, the sprint skiing performance was mainly related to uphill performance, greater use of the G3 technique, and higher DP and G3 maximum velocities. Additionally, VO2max was related to the ability to maintain racing velocity in the uphills and lean body mass was related to starting velocity and DP maximal speed.
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- Apró, William, et al.
(författare)
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Amino Acid-induced S6K1 Activity In Human Skeletal Muscle Is Mediated By Increased mTor/Rheb Interaction : 128 June 1, 11: 15 AM - 11: 30 AM.
- 2016
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Ingår i: Medicine And Science In Sports And Exercise 2016 May; Vol. 48 (5S Suppl 1), pp. 17.. - : Ovid Technologies (Wolters Kluwer Health). ; 48:5 Suppl 1, s. 17-
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Konferensbidrag (refereegranskat)abstract
- Cell culture studies have shown that amino acids activate mTORC1 signaling by increasing the interaction between mTOR and its essential activator Rheb. However, the existence of this mechanism in human skeletal muscle remains to be determined.PURPOSE: To determine if increased mTORC1 signaling in response to amino acids in human skeletal muscle is due to an increased interaction between mTOR and Rheb.METHODS: Eight well trained men performed resistance exercise on two separate occasions. In connection with the exercise, subjects were supplemented with flavored water (Pla) and essential amino acids (EAA) in a double-blind, randomized cross-over design. Muscle biopsies were taken in the vastus lateralis muscle before, immediately after and 90 and 180 min post exercise. Activity of the mTORC1 pathway was assessed by a radiolabeled in-vitro kinase assay for its immediate downstream target S6K1. Protein-protein interactions were determined by western blot following co-immunoprecipitation of mTOR with Rheb. Co-immunoprecipitation was performed on pooled muscle samples from three of the eight subjects.RESULTS: Activity of S6K1 remained unchanged immediately after exercise in both trials. However, at 90 min post exercise, S6K1 activity increased by approximately 2- and 8-fold (p<0.05) from baseline the Pla and EAA trials, respectively. At the 180 min time point, S6K1 activity remained elevated in both trials being approx. 3-fold higher in the Pla trial and 5-fold higher (p<0.05) in the EAA trial. The fold-change in mTOR and Rheb interaction largely resembled the activity pattern of S6K1 in both trials; in the Pla trial the fold-change was 0.9, 1.3 and 1.4 while in the EAA trial the fold-change was 1.6, 2.9 and 1.9 immediately after, 90 min after and 180 min after exercise, respectively.CONCLUSIONS: The large increase in S6K1 activity following EAA intake appears to be mediated by an increased interaction between mTOR and its proximal activator Rheb. This is the first time this mechanism has been demonstrated in human skeletal muscle.
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- Azzinnari, M, et al.
(författare)
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Efectos del ejercicio en la señalización de NF-kB durante la restricción calórica severa
- 2017
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Konferensbidrag (refereegranskat)abstract
- El sobrepeso y la obesidad, en crecimiento en todo el mundo, se asocian con una alta tasa de mortalidad e morbilidad[1,2]. La causa principal que conduce a éstas condiciones patológicas es un balance energético positivo sostenido a largo plazo, debido a la inactividad física y la ingesta calórica excesiva[3]. Por lo tanto, ejercicio físico y restricción calórica podrían ser dos estratégias eficaces para prevenir y contrastar el excesivo acumulo de grasa corporal que caracteriza estas patologías. Sin embargo, durante dietas muy bajas en calorías (<800 Kcal/día) se pierde no solo masa grasa sino también masa muscular, reportando efectos negativos para la salud[4]. En dichas condiciones, el ejercicio físico permite preservar masa muscular de manera local y dosis-dependiente, mientras la ingestión de proteínas no ejerce particulares efectos protectivos sobre el tejido contráctil[5]. Los mecanismos moleculares implicados en la preservación de la masa muscular inducida por el ejercicio durante este tipo de dietas no han sido definidos claramente. NF-kB es un factor de transcripción cuya activación provoca atrofia muscular, y su bloqueo puede parcialmente limitar este fenomeno[6]. NF-kB se ha mostrado activado de manera aguda por el ejercicio y la restricción calorica, sin embargo no ha sido definida su respuesta a la restricción calórica en conjunción con el ejercicio prolongado de baja intensidad. Además, cuando los niveles basales de NF-kB son altos, el ejercicio no parece aumentar ulteriormente su señalización[7]. Por las razones presentadas, NF-kB podría desempeñar un rol en la preservación de masa magra inducida por el ejercicio durante la restricción calórica.El objetivo del estudio es establecer la respuesta de NF-kB a la restricción calórica severa en conjunción con el ejercicio prolongado de baja intensidad. Las hipótesis fueron las siguientes: 1) la restricción calórica severa activaría la via de NF-kB y 2) dicha activación será atenuada por el ejercicio de manera local y dosis-dependiente.15 sujetos con sobrepeso y obesidad fueron sometidos a tres fases experimentales: fase 1, en la que la dieta y el nivel de actividad física de los participantes fue monitorizado durante una semana (PRE); fase 2, caracterizada por cuatro días de ejercicio prolongado y de restricción calórica severa (RCE); fase 3, caracterizada por tres días de ejercicio reducido y una dieta isoenergética (DC). Durante la fase 2, los sujetos ingeriron hidratos de carbono o proteínas (0.8 g/kg peso corporal/día; 320 kcal/día) y hicieron 45 minutos de pedaleo con un solo miembro superior (15% Ppeak) seguidos de 8 horas de caminata (4.5 km/h; 35 km/día). Las biopsias musculares fueron recogidas de ambos los deltoides y del vasto lateral en la fase 1 y después de la fase 2 y 3. Mediante Western blot, se determinó la expresión de NF-κB p105, NF-κB p50, la fosforilación de la Serina 32/36 de IκBα e IκBα total. La composición corporal se midió mediante DXA. Estadística: ANOVA para medidas repetidas.Durante los 4 días de restricción calórica severa el deficit energético fue de 5500 Kcal. Después de la fase 2 los sujetos perdieron menos masa magra en los miembros inferiores y en el brazo ejercitado respecto al brazo de control: 57% (P<0.05) y 29% (P=0.05), respectivamente. Tras la fase 2 y 3, el contenido de p105 y de p50 fue menor en los miembros inferiores respecto a los superiores: efecto extremidad P=0.003 y P=0.024 para p105 y p50, respectivamente. Tras la fase 3, la fosforilación de la Serina 32/36 de IkBα aumentó únicamente en las piernas, mientras la expresión total IkBα fue mayor solo en los miembros ejercitados (P<0.05).El ejercicio físico atenuó la activación de la señalización de NF-kB durante 4 días de restricción calórica severa, limitando el incremento de la expresión de p50 y p105, que resultó más baja después de la fase 2 y la fase 3 en los miembros inferiores respecto a los miembros superiores, posiblemente debido a la mayor cantidad de ejercicio a la que fueron sometidos. Además, la expresión total de IkBα fue más alta tras la fase 3 solo en los miembros ejercitados, indicando una posible inhibición de la vía de NF-kB inducida por el ejercicio. Por lo tanto, dado la menor activación de la señalización de NF-kB en los miembros que perdieron menor masa muscular, los resultados sugieren que los efectos protectores del ejercicio físico sobre el tejido contráctil podrían ser mediados a una menor activación de la señalización de NF-kB.El ejercicio físico desempeña una función preservadora sobre la masa muscular durante la restricción calórica severa. La preservación de masa muscular es dosis-dependiente (a mayor volumen, mayor preservación) y está mediada, al menos parcialmente, por una menor activación de la señalización por NF-kB.1.Hill, J. O., H. R. Wyatt, et al. (2012). Circulation 126(1): 126-132.2.Di Angelantonio, E., N. Bhupathiraju Sh, et al. (2016). Lancet 388(10046): 776-786. 3.Chaston, T. B., J. B. Dixon, et al. (2007). Int J Obes (Lond) 31(5): 743-750. 4.Calbet, J. A., J. G. Ponce-Gonzalez, et al. (2017). Front Physiol (Accepted, In press).5.Cai, D., J. D. Frantz, et al. (2004). Cell 119(2): 285-298.6.Tantiwong, P., K. Shanmugasundaram, et al. (2010). Am J Physiol Endocrinol Metab 299(5): E794-801.7.NCD-RisC (2016). Lancet 387(10026): 1377-1396.
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| 8. |
- Beaven, Martyn, et al.
(författare)
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Physiological comparison of concentric and eccentric arm cycling in males and females
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 5:9, s. Art. no. e112079-
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Tidskriftsartikel (refereegranskat)abstract
- Lower body eccentric exercise is well known to elicit high levels of muscular force with relatively low cardiovascular and metabolic strain. As a result, eccentric exercise has been successfully utilised as an adaptive stressor to improve lower body muscle function in populations ranging from the frail and debilitated, to highly-trained individuals. Here we investigate the metabolic, cardiorespiratory, and energy costs of upper body eccentric exercise in a healthy population. Seven men and seven women performed 4-min efforts of eccentric (ECC) or concentric (CON) arm cycling on a novel arm ergometer at workloads corresponding to 40, 60, and 80% of their peak workload as assessed in an incremental concentric trial. The heart rate, ventilation, cardiac output, respiratory exchange ratio, and blood lactate concentrations were all clearly greater in CON condition at all of the relative workloads (all p<0.003). Effect size calculations demonstrated that the magnitude of the differences in VO2 and work economy between the ECC and CON exercise ranged from very large to extremely large; however, in no case did mechanical efficiency (ηMECH) differ between the conditions (all p>0.05). In contrast, delta efficiency (ηΔ), as previously defined by Coyle and colleagues in 1992, demonstrated a sex difference (men>women; p<0.05). Sex differences were also apparent in arteriovenous oxygen difference and heart rate during CON. Here, we reinforce the high-force, low cost attributes of eccentric exercise which can be generalised to the muscles of the upper body. Upper body eccentric exercise is likely to form a useful adjunct in debilitative, rehabilitative, and adaptive clinical exercise programs; however, reports of a shift towards an oxidative phenotype should be taken into consideration by power athletes. We suggest delta efficiency as a sensitive measure of efficiency that allowed the identification of sex differences.
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| 9. |
- 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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