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1.
Acute Effects of Winter Sports and Indoor Cycling on Arterial Stiffness.
Niebauer, J, Müller, EE, Schönfelder, M, Schwarzl, C, Mayr, B, Stöggl, J, Stöggl, T
Journal of sports science & medicine. 2020;(3):460-468
Abstract
Sedentary lifestyle predisposes to endothelial dysfunction, increased arterial stiffness and cardiovascular diseases, all of which can be positively modified by regular physical exercise training. A decrease in physical activity during winter months coincides with higher rates of cardiovascular events. In order to identify winter sports suitable to overcome this seasonal exercise deficit and thus contribute to cardiovascular health, it was the aim of this study to compare immediate effects of cross-country skiing (XCS) and alpine skiing (AS) on arterial stiffness as an alternative to indoor cycling (IC). After baseline assessment, eighteen healthy subjects performed one session of XCS, AS, and IC in randomized order. Pulse wave analysis was conducted (Mobil-o-Graph®) before and 10-min after exercise. Parameters of arterial stiffness and wave reflection were reduced after XCS and IC, but not after AS: central systolic blood pressure (IC: -8.0 ± 5.4 mmHg; p < 0.001), amplitude of the backward pressure wave (IC: -1.4 ± 2.7 mmHg; p < 0.05), reflection coefficient (XCS: -6.0 ± 7.8%; IC: -5.7 ± 8.1%; both p < 0.1), and pulse wave velocity (IC by -0.19 ± 0.27 m/s; p < 0.01). Higher exercise intensities correlated with greater reductions of arterial stiffness (all p < 0.05). Single sessions of XCS, IC but not AS led to comparable improvement in arterial stiffness, which was even more pronounced during higher exercise intensities. With regard to arterial stiffness, IC and XCS emerge as more effective to counteract the winter exercise deficit and thus the deleterious cardiovascular effects of a sedentary lifestyle.
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2.
Effects of supplementing with an 18% carbohydrate-hydrogel drink versus a placebo during whole-body exercise in -5 °C with elite cross-country ski athletes: a crossover study.
Pettersson, S, Edin, F, Bakkman, L, McGawley, K
Journal of the International Society of Sports Nutrition. 2019;(1):46
Abstract
BACKGROUND Whilst the ergogenic effects of carbohydrate intake during prolonged exercise are well-documented, few investigations have studied the effects of carbohydrate ingestion during cross-country skiing, a mode of exercise that presents unique metabolic demands on athletes due to the combined use of large upper- and lower-body muscle masses. Moreover, no previous studies have investigated exogenous carbohydrate oxidation rates during cross-country skiing. The current study investigated the effects of a 13C-enriched 18% multiple-transportable carbohydrate solution (1:0.8 maltodextrin:fructose) with additional gelling polysaccharides (CHO-HG) on substrate utilization and gastrointestinal symptoms during prolonged cross-country skiing exercise in the cold, and subsequent double-poling time-trial performance in ~ 20 °C. METHODS Twelve elite cross-country ski athletes (6 females, 6 males) performed 120-min of submaximal roller-skiing (69.3 ± 2.9% of [Formula: see text]O2peak) in -5 °C while receiving either 2.2 g CHO-HG·min- 1 or a non-caloric placebo administered in a double-blind, randomized manner. Whole-body substrate utilization and exogenous carbohydrate oxidation was calculated for the last 60 min of the submaximal exercise. The maximal time-trial (2000 m for females, 2400 m for males) immediately followed the 120-min submaximal bout. Repeated-measures ANOVAs with univariate follow-ups were conducted, as well as independent and paired t-tests, and significance was set at P < 0.05. Data are presented as mean ± SD. RESULTS Exogenous carbohydrate oxidation contributed 27.6 ± 6.6% to the total energy yield with CHO-HG and the peak exogenous carbohydrate oxidation rate reached 1.33 ± 0.27 g·min- 1. Compared to placebo, fat oxidation decreased by 9.5 ± 4.8% with CHO-HG, total carbohydrate oxidation increased by 9.5 ± 4.8% and endogenous carbohydrate utilization decreased by 18.1 ± 6.4% (all P < 0.05). No severe gastrointestinal symptoms were reported in either trial and euhydration was maintained in both trials. Time-trial performance (8.4 ± 0.4 min) was not improved following CHO-HG compared to placebo (- 0.8 ± 3.5 s; 95% confidence interval - 3.0 to 1.5 s; P = 0.46). No sex differences were identified in substrate utilization or relative performance. CONCLUSIONS Ingestion of an 18% multiple-transportable carbohydrate solution with gelling polysaccharides was found to be well-tolerated during 120 min of submaximal whole-body exercise, but did not improve subsequent maximal double-poling performance.
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Female Reproductive, Adrenal, and Metabolic Changes during an Antarctic Traverse.
Gifford, RM, O'Leary, T, Cobb, R, Blackadder-Weinstein, J, Double, R, Wardle, SL, Anderson, RA, Thake, CD, Hattersley, J, Imray, CHE, et al
Medicine and science in sports and exercise. 2019;(3):556-567
Abstract
PURPOSE To explore the effects of the first all-female transantarctic expedition on hormonal axes pertinent to reproductive and metabolic function. METHODS Six females (age, 28-36 yr; body mass index, 24.2 ± 0.97 kg·m) hauled 80-kg sledges 1700 km in 61 d. Estimated average energy intake was 20.8 ± 0.1 MJ·d (4970 ± 25 kcal·d). Whole and regional body composition was measured by dual-energy x-ray absorptiometry 1 and 2 months before and 15 d after, the expedition. Body fat was also estimated by skinfold and bioimpedance immediately before and after the expedition. Basal metabolic and endocrine blood markers and, after 0.25 mg dexamethasone suppression, 1-h 10-μg gonadorelin and 1.0 μg adrenocortiocotrophin-(1-24) tests were completed, 39-38 d preexpedition and 4 to 5 d and 15 to 16 d postexpedition. Cortisol was assessed in hair (monthly average concentrations) and saliva (five-point day curves and two-point diurnal sampling). RESULTS Average body mass loss was 9.37 ± 2.31 kg (P < 0.0001), comprising fat mass only; total lean mass was maintained. Basal sex steroids, corticosteroids, and metabolic markers were largely unaffected by the expedition except leptin, which decreased during the expedition and recovered after 15 d, a proportionately greater change than body fat. Luteinizing hormone reactivity was suppressed before and during the expedition, but recovered after 15 d, whereas follicle-stimulating hormone did not change during or after the expedition. Cortisol reactivity did not change during or after the expedition. Basal (suppressed) cortisol was 73.25 ± 45.23 mmol·L before, 61.66 ± 33.11 mmol·L 5 d postexpedition and 54.43 ± 28.60 mmol·L 16 d postexpedition (P = 0.7). Hair cortisol was elevated during the expedition. CONCLUSIONS Maintenance of reproductive and hypothalamic-pituitary-adrenal axis function in women after an extreme physical endeavor, despite energy deficiency, suggests high female biological capacity for extreme endurance exercise.
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4.
Caffeine improves performance in double poling during acute exposure to 2,000-m altitude.
Stadheim, HK, Nossum, EM, Olsen, R, Spencer, M, Jensen, J
Journal of applied physiology (Bethesda, Md. : 1985). 2015;(12):1501-9
Abstract
There is limited research on the physiological effects of caffeine (CAF) ingestion on exercise performance during acute hypoxia. The aim of the present study was therefore to test the effect of placebo (PLA) and CAF (4.5 mg/kg) on double poling (DP) performance during acute hypoxia. Thirteen male subelite cross-country skiers (V̇o2max 72.6 ± 5.68 ml·kg(-1)·min(-1)) were included. Performance was assessed as 1) an 8-km cross-country DP time-trial (C-PT), and 2) time until task failure at a set workload equal to ∼90% of DP V̇o2max. Testing was carried out in a hypobaric chamber, at 800 mbar (Pio2: ∼125 mmHg) corresponding to ∼2,000 m above sea level in a randomized double-blinded, placebo-controlled, cross-over design. CAF improved time to task failure from 6.10 ± 1.40 to 7.22 ± 1.30 min (P < 0.05) and velocity the first 4 km (P < 0.05) but not overall time usage for the 8-km C-PT. During submaximal exercise subjects reported lower pain in arms and rate of perceived exertion (RPE) following CAF ingestion. Throughout C-PTs similar RPE and pain was shown between treatments. However, higher heart rate was observed during the CAF 8 km (187 ± 7 vs. 185 ± 7; P < 0.05) and 90% C-PT (185 ± 7 vs. 181 ± 9) associated with increased ventilation, blood lactate, glucose, adrenaline, decreased pH, and bicarbonate. The present study demonstrates for the first time that CAF ingestion improves DP time to task failure although not consistently time trial performance during acute exposure to altitude. Mechanisms underpinning improvements seem related to reduced pain RPE and increased heart rate during CAF C-PTs.
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Beta-alanine supplementation improves jumping power and affects severe-intensity performance in professional alpine skiers.
Gross, M, Bieri, K, Hoppeler, H, Norman, B, Vogt, M
International journal of sport nutrition and exercise metabolism. 2014;(6):665-73
Abstract
INTRODUCTION Supplementation with beta-alanine may have positive effects on severe-intensity, intermittent, and isometric strength-endurance performance. These could be advantageous for competitive alpine skiers, whose races last 45 to 150 s, require metabolic power above the aerobic maximum, and involve isometric muscle work. Further, beta-alanine supplementation affects the muscle force-frequency relationship, which could influence explosiveness. We explored the effects of beta-alanine on explosive jump performance, severe exercise energy metabolism, and severe-intensity ski-like performance. METHODS Nine male elite alpine skiers consumed 4.8 g/d beta-alanine or placebo for 5 weeks in a double-blind fashion. Before and after, they performed countermovement jumps (CMJ), a 90-s cycling bout at 110% VO2max (CLT), and a maximal 90-s box jump test (BJ90). RESULTS Beta-alanine improved maximal (+7 ± 3%, d = 0.9) and mean CMJ power (+7 ± 2%, d = 0.7), tended to reduce oxygen deficit (-3 ± 8%, p = .06) and lactate accumulation (-12 ± 31%) and enhance aerobic energy contribution (+1.3 ± 2.9%, p = .07) in the CLT, and improved performance in the last third of BJ90 (+7 ± 4%, p = .02). These effects were not observed with placebo. CONCLUSIONS Beta-alanine supplementation improved explosive and repeated jump performance in elite alpine skiers. Enhanced muscle contractility could possibly explain improved explosive and repeated jump performance. Increased aerobic energy production could possibly help explain repeated jump performance as well.
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6.
Caffeine and performance over consecutive days of simulated competition.
Stadheim, HK, Spencer, M, Olsen, R, Jensen, J
Medicine and science in sports and exercise. 2014;(9):1787-96
Abstract
PURPOSE 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 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·min) 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.
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7.
Caffeine increases performance in cross-country double-poling time trial exercise.
Stadheim, HK, Kvamme, B, Olsen, R, Drevon, CA, Ivy, JL, Jensen, J
Medicine and science in sports and exercise. 2013;(11):2175-83
Abstract
PURPOSE Caffeine (CAF) improves performance in both short- and long-duration running and cycling where performance relies on power output and endurance capacity of leg muscles. No studies have so far tested the effects of CAF while using the double-poling (DP) technique in cross-country skiing. When using the DP technique, arm muscles provide the speed-generating force and therefore play an important role in performance outcome. The metabolism of arm muscles differs from that of leg muscles. Thus, results from studies on leg muscles and CAF may not be directly applicable to exercises while using the DP technique in cross-country skiing. The purpose of our study was therefore to investigate the effects of CAF on exercise performance in DP. METHOD Ten highly trained male cross-country skiers (V·O 2max running, 69.3 ± 1.0 mL · kg · min(-1)) performed a placebo (PLA) and CAF trial using a randomized, double-blind, crossover design. Performance was assessed by measuring the time to complete an 8-km cross-country DP performance test (C-PT). CAF (6 mg · kg(-1)) or PLA was ingested 75 min before the C-PT. RESULTS CAF ingestion reduced the time to complete the 8-km C-PT from 34:26 ± 1:25 to 33:01 ± 1:24 min (P < 0.05). The subjects maintained higher speed and HR throughout the C-PT, and lactate was higher immediately after the C-PT with CAF exposure compared with PLA. Subjects reported lower RPE at submaximal intensities during CAF compared with PLA, although HR was similar. CONCLUSION CAF intake enhances endurance performance in an 8-km C-PT, where arm muscles limit performance. CAF ingestion allowed the participants to exercise with a higher HR and work intensity possibly by reducing perception of effort or facilitating motor unit recruitment.
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Dietary nitrate does not enhance running performance in elite cross-country skiers.
Peacock, O, Tjønna, AE, James, P, Wisløff, U, Welde, B, Böhlke, N, Smith, A, Stokes, K, Cook, C, Sandbakk, O
Medicine and science in sports and exercise. 2012;(11):2213-9
Abstract
PURPOSE The objective of this study is to examine the effects of acute ingestion of dietary nitrate on endurance running performance in highly trained cross-country skiers. Dietary nitrate has been shown to reduce the oxygen cost of submaximal exercise and improve tolerance of high-intensity exercise, but it is not known if this holds true for highly trained endurance athletes. METHODS Ten male junior cross-country skiers (V˙O(2max)) ≈ 70 mL·kg·min) each completed two trials in a randomized, double-blind design. Participants ingested potassium nitrate (614-mg nitrate) or a nitrate-free placebo 2.5 h before two 5-min submaximal tests on a treadmill at 10 km·h (≈55% of V˙O(2max)) and 14 km·h (≈75% of V˙O(2max)), followed by a 5-km running time trial on an indoor track. RESULTS Plasma nitrite concentrations were higher after nitrate supplementation (325 ± 95 nmol·L) compared with placebo (143 ± 59 nmol·L, P < 0.001). There was no significant difference in 5-km time-trial performance between nitrate (1005 ± 53 s) and placebo treatments (996 ± 49 s, P = 0.12). The oxygen cost of submaximal running was not significantly different between placebo and nitrate trials at 10 km·h (both 2.84 ± 0.34 L·min) and 14 km·h (3.89 ± 0.39 vs. 3.77 ± 0.62 L·min). CONCLUSIONS Acute ingestion of dietary nitrate may not represent an effective strategy for reducing the oxygen cost of submaximal exercise or for enhancing endurance exercise performance in highly trained cross-country skiers.
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Human skeletal muscle glycogen utilization in exhaustive exercise: role of subcellular localization and fibre type.
Nielsen, J, Holmberg, HC, Schrøder, HD, Saltin, B, Ortenblad, N
The Journal of physiology. 2011;(Pt 11):2871-85
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Abstract
Although glycogen is known to be heterogeneously distributed within skeletal muscle cells, there is presently little information available about the role of fibre types, utilization and resynthesis during and after exercise with respect to glycogen localization. Here, we tested the hypothesis that utilization of glycogen with different subcellular localizations during exhaustive arm and leg exercise differs and examined the influence of fibre type and carbohydrate availability on its subsequent resynthesis. When 10 elite endurance athletes (22 ± 1 years, VO2 max = 68 ± 5 ml kg-1 min-1, mean ± SD) performed one hour of exhaustive arm and leg exercise, transmission electron microscopy revealed more pronounced depletion of intramyofibrillar than of intermyofibrillar and subsarcolemmal glycogen. This phenomenon was the same for type I and II fibres, although at rest prior to exercise, the former contained more intramyofibrillar and subsarcolemmal glycogen than the latter. In highly glycogen-depleted fibres, the remaining small intermyofibrillar and subsarcolemmal glycogen particles were often found to cluster in groupings. In the recovery period, when the athletes received either a carbohydrate-rich meal or only water the impaired resynthesis of glycogen with water alone was associated primarily with intramyofibrillar glycogen. In conclusion, after prolonged high-intensity exercise the depletion of glycogen is dependent on subcellular localization. In addition, the localization of glycogen appears to be influenced by fibre type prior to exercise, as well as carbohydrate availability during the subsequent period of recovery. These findings provide insight into the significance of fibre type-specific compartmentalization of glycogen metabolism in skeletal muscle during exercise and subsequent recovery. .
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Glucose homeostasis and cardiovascular disease biomarkers in older alpine skiers.
Dela, F, Niederseer, D, Patsch, W, Pirich, C, Müller, E, Niebauer, J
Scandinavian journal of medicine & science in sports. 2011;:56-61
Abstract
Alpine skiing and ski training involves elements of static and dynamic training, and may therefore improve insulin sensitivity. Healthy men and women who where beginners/intermediate level of alpine skiing, were studied before (Pre) and immediately after (Post) 12 weeks of alpine ski training. After an additional 8 weeks a third test (retention study, Ret) was performed. The subjects were randomized into an intervention group (IG, n=22, age=66.6 ± 0.4 years) or a control group (CG, n=20, age=67.0 ± 1.0 years). Plasma glucose decreased (P<0.05) in CG, but increased (P<0.05) again at Ret, while a continued decrease was seen in IG (Ret vs Post, P<0.05). Plasma insulin decreased (P<0.05) with training in IG, while no effect was seen in CG. HOMA2 index for insulin resistance decreased (P<0.05) from 0.80 ± 0.08 to 0.71 ± 0.09 in IG. The value at Ret (0.57 ± 0.08) tended (P=0.067) to be different from Post. In CG the corresponding values were 0.84 ± 0.09, 0.81 ± 0.12 and 0.70 ± 0.09, respectively. Total cholesterol and LDL decreased in both IC and CG, a result, interpreted as seasonal variation. Biomarkers for endothelial function and low-grade inflammation were not elevated and similar in IG and CG, and did not change. Alpine ski training improves glucose homeostasis and insulin sensitivity in healthy, elderly individuals.