Silvana Bucher Sandbakk

Effects of Acute Supplementation of L-arginine and Nitrate on Endurance and Sprint Performance in Elite Athletes

This study examined the effects of acute supplementation with L-arginine and nitrate on running economy, endurance and sprint performance in endurance-trained athletes. In a randomised cross-over, double-blinded design we compared the effects of combined supplementation with 6 g L-arginine and 614 mg nitrate against 614 mg nitrate alone and placebo in nine male elite cross-country skiers (age 18 ± 0 years, VO2max 69.3 ± 5.8 ml ⋅ min(-1) ⋅ kg(-1)). After a 48-hour standardisation of nutrition and exercise the athletes were tested for plasma nitrate and nitrite concentrations, blood pressure, submaximal running economy at 10 km ⋅ h(-1) and 14 km ⋅ h(-1) at 1% incline and 180 m as well as 5-km time-trial running performances. Plasma nitrite concentration following L-arginine + nitrate supplementation (319 ± 54 nmol ⋅ L(-1)) did not differ from nitrate alone (328 ± 107 nmol ⋅ L(-1)), and both were higher than placebo (149 ± 64 nmol ⋅ L(-1), p < 0.01). There were no differences in physiological responses during submaximal running or in 5-km performance between treatments. The plasma nitrite concentrations indicate greater nitric oxide availability both following acute supplementation of L-arginine + nitrate and with nitrate alone compared to placebo, but no additional effect was revealed when L-arginine was added to nitrate. Still, there were no effects of supplementation on exercise economy or endurance running performance in endurance-trained cross-country skiers.

Downhill turn techniques and associated physical characteristics in cross-country skiers

Three dominant techniques are used for downhill turning in cross‐country skiing. In this study, kinematic, kinetic, and temporal characteristics of these techniques are described and related to skier strength and power. Twelve elite female cross‐country skiers performed six consecutive turns of standardized geometry while being monitored by a Global Navigation Satellite System. Overall time was used as an indicator of performance. Skiing and turning parameters were determined from skier trajectories; the proportional use of each technique was determined from video analysis. Leg strength and power were determined by isometric squats and countermovement jumps on a force plate. Snow plowing, parallel skidding, and step turning were utilized for all turns. Faster skiers employed less snow plowing and more step turning, more rapid deceleration and earlier initiation of step turning at higher speed (r = 0.80–0.93; all P < 0.01). Better performance was significantly correlated to higher mean speed and shorter trajectory (r = 0.99/0.65; both P < 0.05) and to countermovement jump characteristics of peak force, time to peak force, and rate of force development (r = −0.71/0.78/−0.83; all P < 0.05). In conclusion, faster skiers used step turning to a greater extent and exhibited higher maximal leg power, which enabled them to combine high speeds with shorter trajectories during turns.

Personal Activity Intelligence (PAI), Sedentary Behavior and Cardiovascular Risk Factor Clustering – the HUNT Study

Prolonged sedentary behavior (SB) positively associates with clustering of risk factors for cardiovascular disease (CVD). The recently developed metric for physical activity (PA) tracking called Personal Activity Intelligence (PAI) takes into account age, sex, resting and maximum heart rate, and a score of ≥100 weekly PAI has been shown to reduce the risk of premature CVD death in healthy as well as individuals with known CVD risk factors, regardless of whether or not the current PA recommendations were met. The aim of the present study was to examine if PAI modifies the associations between SB and CVD risk factor (CV-RF) clustering in a large apparently healthy general population cohort (n=29,950, aged ≥20 years). Logistic regression revealed that in those with ≥100 weekly PAI, the likelihood of CV-RF clustering prevalence associated with prolonged SB was attenuated across age groups. Monitoring weekly PAI-level could be useful to ensure that people perform enough PA to combat SBs deleterious association with CV-RF.

Sedentary Time, Cardiorespiratory Fitness, and Cardiovascular Risk Factor Clustering in Older Adults--the Generation 100 Study

OBJECTIVE To determine whether meeting physical activity (PA) recommendations and/or having high age-specific cardiorespiratory fitness (CRF) attenuate the adverse effect of prolonged sedentary time on cardiovascular risk factor (CV-RF) clustering in older adults. PATIENTS AND METHODS We conducted a cross-sectional study of Norwegian women (495) and men (379) aged 70 to 77 years from August 22, 2012, through June 30, 2013. Sedentary time and PA were assessed by accelerometers and CRF by directly measured peak oxygen uptake (VO2peak). Logistic regression was used to estimate adjusted odds ratios (ORs) and CIs for the association between sedentary time and prevalence of CV-RF clustering (≥3 of the following: hypertension, high blood glucose level, high waist circumference, low high-density lipoprotein cholesterol level, or high triglyceride level) and for the modifying effect of PA and CRF. RESULTS Overall, 163 of the 495 women (32.9%) and 140 of the 379 men (36.9%) had CV-RF clustering. Each additional hour of sedentary time was associated with 22% (OR, 1.22; 95% CI, 1.02-1.45) and 27% (OR, 1.27; 95% CI, 1.04-1.55) higher likelihood of having CV-RF clustering in women and men, respectively, whereas a 1-metabolic equivalent decrement in VO2peak corresponded to 57% (OR, 1.57; 95% CI, 1.34-1.84) and 67% (OR, 1.67; 95% CI, 1.44-1.95) higher likelihood of CV-RF clustering in women and men, respectively. High CRF (VO2peak >27.5 mL/kg per minute in women and >34.4 mL/kg per minute in men) attenuated the adverse effects of high sedentary time on CV-RF clustering, even among individuals not meeting recommendations for PA. CONCLUSION High age-specific CRF fully attenuates the adverse effect of prolonged sedentary time on CV-RF clustering, independent of meeting the PA consensus recommendation in older adults.

The Velocity and Energy Profiles of Elite Cross-Country Skiers Executing Downhill Turns With Different Radii

This study examined the influence of turn radius on velocity and energy profiles when skidding and step turning during more and less effective downhill turns while cross-country skiing. Thirteen elite female cross-country skiers performed single turns with a 9- or 12-m radius using the skidding technique and a 12- or 15-m radius with step turning. Mechanical parameters were monitored using a real-time kinematic Global Navigation Satellite System and video analysis. Step turning was more effective during all phases of a turn, leading to higher velocities than skidding (P < .05). With both techniques, a greater radius was associated with higher velocity (P < .05), but the quality of turning, as assessed on the basis of energy characteristics, was the same. More effective skidding turns involved more pronounced deceleration early in the turn and maintenance of higher velocity thereafter, while more effective step turning involved lower energy dissipation during the latter half of the turn. In conclusion, the single-turn analysis employed here reveals differences in the various techniques chosen by elite cross-country skiers when executing downhill turns of varying radii and can be used to assess the quality of such turns.

Cardiorespiratory Reference Data in Older Adults: The Generation 100 Study.

Purpose Cardiorespiratory fitness (CRF) is regarded a clinical vital sign, and accurate reference values for all age groups are essential. Little data exist on CRF and cardiorespiratory function in older adults. The aim of this study was to provide normative values for CRF and cardiorespiratory function in older adults, including people with history of cardiovascular diseases (CVD). Methods In total, 1537 (769 women) participants age 70 to 77 yr underwent clinical examinations and cardiopulmonary exercise tests. Peak oxygen uptake (V˙O2peak), ventilation (V˙Epeak), expiration of carbon dioxide (VV˙CO2peak), breathing frequency (BFpeak), tidal volume (VTpeak), oxygen pulse (O2 pulsepeak), ventilatory efficiency (EqV˙O2peak and EqV˙CO2peak), and 1-min HR recovery were assessed. Results Men compared with women had higher V˙O2peak (31.3 ± 6.7 vs 26.2 ± 5.0 mL·min−1·kg−1), BFpeak (41.8 ± 8.0 vs 39.7 ± 7.1 breaths per minute), VTpeak (2.3 ± 0.5 vs 1.6 ± 0.3), O2 pulsepeak (16.4 ± 3.2 vs 11.3 ± 2.0), V˙CO2peak (2.9 ± 0.2 and 1.9 ± 0.1 L·min−1), V˙Epeak (96.2 ± 21.7 vs 61.1 ± 21.6 L·min−1), EqV˙O2peak (38.0 ± 6.9 vs 35.1 ± 5.6), and EqV˙CO2peak (33.5 ± 5.7 vs 31.9 ± 4.5). Women and men with CVD had lower V˙O2peak (14% and 19%), peak HR (5% and 6%), V˙Epeak (8% and 10%), VTpeak (7% and 4%), and lower EqV˙CO2peak (4% and 6%) compared with their healthy counterparts, respectively. Compared with healthy women and men, 1-min HR recovery was 12% and 16% lower for women and men with CVD. Conclusions This study represents the largest reference material on directly measured CRF and cardiorespiratory function in older men and women, with and without CVD. This novel information will help researchers and clinicians to interpret data form cardiopulmonary testing in older adults.

Combined Association of Cardiorespiratory Fitness and Body Fatness With Cardiometabolic Risk Factors in Older Norwegian Adults: The Generation 100 Study

Objective To investigate the independent and combined associations of fitness and fatness with cardiometabolic risk factors in older Norwegian women and men. Patients and Methods We conducted a cross-sectional study of 505 women and 417 men aged 70 to 77 years enrolled in the Generation 100 study in Norway. Fitness was assessed as peak oxygen uptake and fatness as high body mass index (BMI; ≥25 kg/m2), waist circumference (WC) of 88 cm or greater for women and 102 cm or greater for men, and percent body fat (%BF) of 35% or greater and 25% or greater for women and men, respectively. High cardiometabolic risk was defined as the presence of 2 or more of the following risk factors: elevated triglyceride level, reduced high-density lipoprotein cholesterol concentration, elevated blood pressure, and elevated fasting glucose level or pharmacological treatment of these conditions. Results Receiver operating characteristic curve analyses identified fitness levels of less than 25.7 and less than 30.7 mL/kg per minute in women and men, respectively, as critical thresholds for having high cardiometabolic risk. Individuals with levels below these thresholds had an adjusted odds ratio of 2.77 (95% CI, 2.09-3.66) for having high cardiometabolic risk, while high BMI, WC, and %BF had odds ratios (95% CIs) of 3.58 (2.69-4.77), 3.06 (2.29-4.10), and 3.26 (2.47-4.30), respectively. In our combined analyses, being lean did not attenuate the cardiometabolic risk associated with low fitness, and combinations of low fitness and/or high BMI, WC, or %BF cumulatively increased cardiometabolic risk. Conclusion Low fitness and indication of fatness were independently and cumulatively associated with poor cardiometabolic health. Our results emphasize the importance of including both physical fitness and body fatness in the assessment of cardiometabolic risk and health promotion efforts in older adults.