Double-Poling Physiology and Kinematics of Elite Cross-Country Skiers: Specialized Long-Distance Versus All-Round Skiers

Purpose: Long-distance cross-country skiers specialize to compete in races >50 km predominantly using double poling (DP). This emphasizes the need for highly developed upper-body endurance capacities and an efficient DP technique. The aim of this study was to investigate potential effects of specialization by comparing physiological capacities and kinematics in DP between long-distance skiers and skiers competing using both techniques (skating/classic) in several competition formats (“all-round skiers”). Methods: Seven male long-distance (32 [6] y, 183 [6] cm, 76 [5] kg) and 6 all-round (25 [3] y, 181 [5] cm, 75 [6] kg) skiers at high international levels conducted submaximal workloads and an incremental test to exhaustion for determination of peak oxygen uptake (VO2peak) and time to exhaustion (TTE) in DP and running. Results: In DP and running maximal tests, TTE showed no difference between groups. However, long-distance skiers had 5–6% lower VO2peak in running (81 [5] vs 85 [3] mL·kg−1·min−1; P = .07) and DP (73 [3] vs 78 [3] mL·kg−1·min−1; P < .01) than all-round skiers. In DP, long-distance skiers displayed lower submaximal O2 cost than all-round skiers (3.8 ± 3.6%; P < .05) without any major differences in cycle times or cyclic patterns of joint angles and center of mass. Lactate concentration over a wide range of speeds (45–85% of VO2peak) did not differ between groups, even though each workload corresponded to a slightly higher percentage of VO2peak for long-distance skiers (effect size: 0.30–0.68). Conclusions: The long-distance skiers displayed lower VO2peak but compensated with lower O2 cost to perform equally with the all-round skiers on a short TTE test in DP. Furthermore, similar submaximal lactate concentration and reduced O2 cost could be beneficial in sustaining high skiing speeds in long-duration competitions

Caffeine Increases Exercise Performance, Maximal Oxygen Uptake, and Oxygen Deficit in Elite Male Endurance Athletes.

PURPOSE: The aims of the present study were to test the hypothesis that caffeine increases maximal oxygen uptake (V˙O2max) and to characterize the physiological mechanisms underpinning improved high-intensity endurance capacity. METHODS: Twenty-three elite endurance-trained male athletes were tested twice with and twice without caffeine (four tests) in a randomized, double-blinded, and placebo-controlled study with crossover design. Caffeine (4.5 mg·kg-1) or placebo was consumed 45 min before standardized warm-up. Time to exhaustion during an incremental test (running 10.5° incline, start speed 10.0 km·h-1, and 0.5 km·h-1 increase in speed every 30 s) determined performance. Oxygen uptake was measured continuously to determine V˙O2max and O2 deficit was calculated. RESULTS: Caffeine increased time to exhaustion from 355 ± 41 to 375 ± 41 s (Δ19.4 ± 16.5 s; P < 0.001). Importantly, caffeine increased V˙O2max from 75.8 ± 5.6 to 76.7 ± 6.0 mL·kg-1·min-1 (Δ 0.9 ± 1.7 mL·kg-1·min-1; P < 0.003). Caffeine increased maximal heart rate (HRpeak) and ventilation (VEpeak). Caffeine increased O2 deficit from 63.1 ± 18.2 to 69.5 ± 17.5 mL·kg-1 (P < 0.02) and blood lactate compared with placebo. The increase in time to exhaustion after caffeine ingestion was reduced to 11.7 s after adjustment for the increase in V˙O2max. Caffeine did not significantly increase V˙O2max after adjustment for VEpeak and HRpeak. Adjustment for O2 deficit and lactate explained 6.2 s of the caffeine-induced increase in time to exhaustion. The increase in V˙O2max, VE, HR, O2 deficit, and lactate explained 63% of the increased performance after caffeine intake. CONCLUSION: Caffeine increased V˙O2max in elite athletes, which contributed to improvement in high-intensity endurance performance. Increases in O2 deficit and lactate also contributed to the caffeine-induced improvement in endurance performance.Disclosure of funding received for this work from any of the following organizations: National Institutes of Health (NIH); Welcome Trust; Howard Hughes Medical Institute (HHMI); and other(s)

Caffeine and performance over consecutive days of simulated competition

I Brage finner du siste tekst-versjon av artikkelen, og den kan inneholde ubetydelige forskjeller fra forlagets pdf-versjon. Forlagets pdf-versjon finner du på www.ovid.com: http://dx.doi.org/10.1249/MSS.0000000000000288 / In Brage you'll find the final text version of the article, and it may contain insignificant differences from the journal's pdf version. The definitive version is available at www.ovid.com: http://dx.doi.org/10.1249/MSS.0000000000000288Purpose: Performance improvements after caffeine (CAF) ingestion are well documented when using a 1-d protocol. In numerous competitions such as the Tour de France, Tour de Ski, world championships, and National College Athletic Association championships, athletes compete for several days in a row. To date, no studies have investigated the effects of CAF when competing for consecutive days in a row. This study aimed to investigate the effects of placebo (PLA) and two different CAF doses (3 and 4.5 mg·kg-1 body mass) on performance in a 10-min all-out, cross-country, double poling ergometer test (C-PT) 2 d in a row. Method: Eight highly trained male cross-country skiers (V·O2max-run, 78.5 ± 1.6 mL·kg-1·min-1) participated in the study, which was a randomized, double-blind, PLA-controlled, crossover design. Performance was assessed as distance covered during a 10-min all-out C-PT. Oral ingestion of CAF or PLA was consumed 75 min before the all-out C-PT. Results: Poling distance was improved after CAF ingestions compared with that after PLA on both days. The improvements on day 1 were 4.0% (90% confidence limits, ±3.3) and 4.0% ± 2.9% for both CAF doses, respectively (P < 0.05), whereas improvements on day 2 were 5.0% ± 3.6% and 5.1% ± 2.8% for CAF3 and CAF4.5, respectively, compared with those for PLA. Improved performance was associated with increased HR, adrenaline concentration, blood lactate concentration, and V·O2 consumption after CAF ingestion. Furthermore, performance was elevated despite higher creatine kinase concentration and muscular pain at arrival on day 2 for both CAF doses. Conclusions: Both CAF doses improved performance in the 10-min all-out C-PT compared with PLA over two consecutive days. Therefore, CAF seems useful for athletes competing over consecutive days despite higher muscle damage occurring after enhanced performance on the first day.Seksjon for fysisk prestasjonsevne / Department of Physical Performanc

The Influence of Pole Length on Performance, O2-Cost and Kinematics in Double Poling

Purpose: In the double poling cross-country skiing technique, the propulsive forces are transferred solely through the poles. The aim of the present study was to investigate how pole length influences double poling performance, O2-cost and kinematics during treadmill roller skiing. Methods: Nine male competitive cross-country skiers (24±3 yrs, 180±5 cm, 72±5 kg, VO2max running: 76±6 mL·kg-1·min-1) completed two identical test protocols using self-selected (84±1% of body height) and long poles (self-selected + 7.5 cm; 88±1% of body height) in a counter-balanced fashion. Each test protocol included a 5-minute warm-up (2.5 m·s-1; 2.5°), three 5-min submaximal sessions (3.0, 3.5 and 4.0 m·s-1; 2.5°) for assessment of O2-cost, followed by a self-paced 1000-m time trial (~3 min, >5.0 m·s-1; 2.5°). Temporal patterns and kinematics were assessed using accelerometers and 2D video. Results: Long poles reduced 1000-m time (mean±90% confidence interval; -1.0±0.7%, P=0.054) and submaximal O2-cost (-2.7±1.0%, P=0.002) compared to self-selected poles. The center of mass vertical range of displacement tended to be smaller for long than for self-selected poles (23.3±3.0 vs. 24.3±3.0 cm, P=0.07). Cycle and reposition time did not differ between pole lengths at any speeds tested, whereas poling time tended to be shorter for self-selected than for long poles at the lower speeds (≤ 3.5 m·s-1, P≤0.10), but not at the higher speeds (≥4.0 m·s-1, P≥0.23). Conclusion: Double poling 1000-m time, submaximal O2-cost and center of mass vertical range of displacement were reduced in competitive cross-country skiers using poles 7.5 cm longer than self-selected ones

Subsarcolemmal lipid droplet responses to a combined endurance and strength exercise intervention

Muscle lipid stores and insulin sensitivity have a recognized association although the mechanism remains unclear. We investigated how a 12‐week supervised combined endurance and strength exercise intervention influenced muscle lipid stores in sedentary overweight dysglycemic subjects and normal weight control subjects (n = 18). Muscle lipid stores were measured by magnetic resonance spectroscopy (MRS), electron microscopy (EM) point counting, and direct EM lipid droplet measurements of subsarcolemmal (SS) and intramyofibrillar (IMF) regions, and indirectly, by deep sequencing and real‐time PCR of mRNA of lipid droplet‐associated proteins. Insulin sensitivity and VO2max increased significantly in both groups after 12 weeks of training. Muscle lipid stores were reduced according to MRS at baseline before and after the intervention, whereas EM point counting showed no change in LD stores post exercise, indicating a reduction in muscle adipocytes. Large‐scale EM quantification of LD parameters of the subsarcolemmal LD population demonstrated reductions in LD density and LD diameters. Lipid droplet volume in the subsarcolemmal LD population was reduced by ~80%, in both groups, while IMF LD volume was unchanged. Interestingly, the lipid droplet diameter (n = 10 958) distribution was skewed, with a lack of small diameter lipid droplets (smaller than ~200 nm), both in the SS and IMF regions. Our results show that the SS LD lipid store was sensitive to training, whereas the dominant IMF LD lipid store was not. Thus, net muscle lipid stores can be an insufficient measure for the effects of training

Higher lipid turnover and oxidation in cultured human myotubes from athletic versus sedentary young male subjects

In this study we compared fatty acid (FA) metabolism in myotubes established from athletic and sedentary young subjects. Six healthy sedentary (maximal oxygen uptake (VO2max)≤ 46 ml/kg/min) and six healthy athletic (VO2max> 60 ml/kg/min) young men were included. Myoblasts were cultured and diferentiated to myotubes from satellite cells isolated from biopsy of musculus vastus lateralis. FA metabolism was studied in myotubes using [14C]oleic acid. Lipid distribution was assessed by thin layer chromatography, and FA accumulation, lipolysis and re-esterifcation were measured by scintillation proximity assay.Gene and protein expressions were studied. Myotubes from athletic subjects showed lower FA accumulation, lower incorporation of FA into total lipids, triacylglycerol (TAG), diacylglycerol and cholesteryl ester, higherTAG-related lipolysis and re-esterifcation, and higher complete oxidation and incomplete β-oxidation of FA compared to myotubes from sedentary subjects. mRNA expression of the mitochondrial electron transport chain complex III gene UQCRB was higher in cells from athletic compared to sedentary. Myotubes established from athletic subjects have higher lipid turnover and oxidation compared to myotubes from sedentary subjects.Our fndings suggestthat cultured myotubes retain some of the phenotypic traits of their donors

Higher lipid turnover and oxidation in cultured human myotubes from athletic versus sedentary young male subjects

In this study we compared fatty acid (FA) metabolism in myotubes established from athletic and sedentary young subjects. Six healthy sedentary (maximal oxygen uptake (VO2max)≤ 46 ml/kg/min) and six healthy athletic (VO2max> 60 ml/kg/min) young men were included. Myoblasts were cultured and diferentiated to myotubes from satellite cells isolated from biopsy of musculus vastus lateralis. FA metabolism was studied in myotubes using [14C]oleic acid. Lipid distribution was assessed by thin layer chromatography, and FA accumulation, lipolysis and re-esterifcation were measured by scintillation proximity assay.Gene and protein expressions were studied. Myotubes from athletic subjects showed lower FA accumulation, lower incorporation of FA into total lipids, triacylglycerol (TAG), diacylglycerol and cholesteryl ester, higherTAG-related lipolysis and re-esterifcation, and higher complete oxidation and incomplete β-oxidation of FA compared to myotubes from sedentary subjects. mRNA expression of the mitochondrial electron transport chain complex III gene UQCRB was higher in cells from athletic compared to sedentary. Myotubes established from athletic subjects have higher lipid turnover and oxidation compared to myotubes from sedentary subjects.Our fndings suggestthat cultured myotubes retain some of the phenotypic traits of their donors

Glucose metabolism and metabolic flexibility in cultured skeletal muscle cells is related to exercise status in young male subjects

We hypothesised that skeletal muscles of healthy young people have a large variation in oxidative capacity and fibre-type composition, and aimed therefore to investigate glucose metabolism in biopsies and myotubes isolated from musculus vastus lateralis from healthy males with varying degrees of maximal oxygen uptake. Trained and intermediary trained subjects showed higher carbohydrate oxidation in vivo. Fibre-type distribution in biopsies and myotubes did not differ between groups. There was no correlation between fibre-type I expression in biopsies and myotubes. Myotubes from trained had higher deoxyglucose accumulation and fractional glucose oxidation (glucose oxidation relative to glucose uptake), and were also more sensitive to the suppressive action of acutely added oleic acid to the cells. Despite lack of correlation of fibre types between skeletal muscle biopsies and cultured cells, myotubes from trained subjects retained some of their phenotypes in vitro with respect to enhanced glucose metabolism and metabolic flexibility

Interaction between plasma fetuin-A and free fatty acids predicts changes in insulin sensitivity in response to long-term exercise

The hepatokine fetuin‐A can together with free fatty acids (FFAs) enhance adipose tissue (AT) inflammation and insulin resistance via toll‐like receptor 4 (TLR4). Although some of the health benefits of exercise can be explained by altered release of myokines from the skeletal muscle, it is not well documented if some of the beneficial effects of exercise can be explained by altered secretion of hepatokines. The aim of this study was to examine the effect of interaction between fetuin‐A and FFAs on insulin sensitivity after physical exercise. In this study, 26 sedentary men who underwent 12 weeks of combined endurance and strength exercise were included. Insulin sensitivity was measured using euglycemic‐hyperinsulinemic clamp, and AT insulin resistance was indicated by the product of fasting plasma concentration of FFAs and insulin. Blood samples and biopsies from skeletal muscle and subcutaneous AT were collected. Several phenotypic markers were measured, and mRNA sequencing was performed on the biopsies. AT macrophages were analyzed based on mRNA markers. The intervention improved hepatic parameters, reduced plasma fetuin‐A concentration (~11%, P < 0.01), slightly changed FFAs concentration, and improved glucose infusion rate (GIR) (~33%, P < 0.01) across all participants. The change in circulating fetuin‐A and FFAs interacted to predict some of the change in GIR (β = −42.16, P = 0.030), AT insulin resistance (β = 0.579, P = 0.003), gene expression related to TLR‐signaling in AT and AT macrophage mRNA (β = 94.10, P = 0.034) after exercise. We observed no interaction effects between FFAs concentrations and leptin and adiponectin on insulin sensitivity, or any interaction effects between Fetuin‐A and FFAs concentrations on skeletal muscle TLR‐signaling. The relationship between FFAs levels and insulin sensitivity seemed to be specific for fetuin‐A and the AT. Some of the beneficial effects of exercise on insulin sensitivity may be explained by changes in circulating fetuin‐A and FFAs, promoting less TLR4 signaling in AT perhaps by modulating AT macrophages