Beetroot supplementation improves the physiological responses to incline walking

The final publication is available at Springer via http://dx.doi.org/10.1007/s00421-018-3843-xPurpose: We investigated the effects of an acute 24-h nitrate-rich beetroot juice supplement (BR) on the energy cost, exercise efficiency and blood pressure responses to intermittent walking at different gradients. Methods: In a double-blind, cross-over design, eight participants were provided with a total of 350 ml of nitrate-rich (~20.5 mmol nitrate) BR or placebo (PLA) across 24-h before completing intermittent walking at 3 km/h on treadmill at gradients of 1%, 5%, 10%, 15% and 20%. Results: Resting mean arterial pressure (MAP) was ~4.1% lower after BR (93 vs. 89 mmHg; P = 0.001), as well as during exercise (102 vs. 99 mmHg; P = 0.011) and recovery (97 vs. 94 mmHg; P = 0.001). Exercising (1227 vs. 1129 ml/min P < 0.001) and end-stage (1404 vs. 1249 ml/min; P = 0.002) oxygen uptake (O2) was lower in BR compared to PLA, which was accompanied by an average reduction in phase II ̇O2 amplitude (1067 vs. 940 ml/min; P = 0.025). Similarly, recovery O2 (509 vs. 458 ml/min; P = 0.001) was lower in BR. Whole-blood potassium concentration increased from pre-post exercise in PLA (4.1 ± 0.3 vs. 4.5 ± 0.3 mmol/L; P = 0.013) but not BR (4.1 ± 0.31 vs. 4.3 ± 0.2 mmol/L; P = 0.188). Conclusions: Energy cost of exercise, recovery of O2, MAP and blood markers were ameliorated after BR. Previously reported mechanisms explain these findings, which are more noticeable during less efficient walking at steep gradients (15-20%). These findings have practical implications for hill-walkers

The Self-Paced VO2max Test to Assess Maximal Oxygen Uptake in Highly Trained Runners.

PURPOSE The novel self-paced maximal oxygen uptake (VO2max) test (SPV) may be a more suitable alternative to traditional maximal tests for elite athletes due to the ability to self-regulate pace. This study aimed to examine whether the SPV can be administered on a motorised treadmill. METHODS Fourteen highly trained male distance runners performed a standard GXT, an incline-based SPV (SPVinc) and a speed-based SPV (SPVsp). The GXT included a plateau verification stage. Both SPV protocols included 5 x 2 minute stages [and a plateau verification stage] and allowed for self-pacing based on fixed increments of rating of perceived exertion (RPE): 11, 13, 15, 17 and 20. The participants varied their speed/incline on the treadmill by moving between different marked 'zones', in which the tester would then adjust the intensity. RESULTS There was no significant difference (p=0.319, ES=0.21) in the VO2max achieved in the SPVsp (67.6 ± 3.6 mL·kg-1·min-1, 95%CI = 65.6 - 69.7 mL·kg-1·min-1) compared to that achieved in the GXT (68.6 ± 6.0 mL·kg-1·min-1, CI = 65.1 - 72.1 mL·kg-1·min-1). Participants achieved a significantly higher VO2max in the SPVinc (70.6 ± 4.3 mL·kg-1·min-1, 95%CI = 68.1 - 73.0 mL·kg-1·min-1) compared to both the GXT (p=0.027, ES=0.39) and SPVsp (p=0.001, ES=0.76). CONCLUSIONS The SPVsp protocol produces similar VO2max values to those obtained in the GXT and may represent a more appropriate and athlete-friendly test which is more orientated towards the variable speed found in competitive sport

Prediction of Race Performance of Elite Cross-Country Skiers by Lean Mass

Purpose: To investigate the relationship between race performance and lean mass (LM) variables, as well as to examine sex differences in body composition in elite-standard cross-country skiers. Methods: Thirty-four elite cross-country skiers (18 men and 16 women) underwent a dual-emission x-ray absorptiometry body composition test to determine LM, fat mass, and bone mineral content. For both sexes, performance data were collected from a sprint prologue and a distance race. Results: The absolute expression of LM variables [whole body (LMWB), upper body (LMUB), and lower body (LMLB)] was significantly correlated with finishing time in the sprint prologue independent of sex. Distance-race performance was significantly related to LMWB, LMUB, and LMLB in women; however, no correlation was found in men. Men had a significantly higher LM and lower fat mass, independent of expression (absolute or relative), for the whole body, arms, trunk, and legs, except for the absolute fat mass in the trunk. Conclusions: The absolute expressions of LMWB, LMUB, and LMLB were significant predictors of sprint-prologue performance in both sexes, as well as of distance-race performance in women only. Compared with women, male skiers have a higher LM in the body segments that are major contributors to propelling forces. These results suggest that muscle mass in the lower and upper body is equally important for race performance; thus, more focus of elite skiers’ training should be directed to increasing whole-body muscle mass to improve their competitive performance capability.</p

Acute hormonal and force responses to combined strength and endurance loadings in men and women: the “order effect”

Purpose To examine acute responses and recovery of serum hormones and muscle force following combined strength (S) and endurance (E) loading sessions in which the order of exercises is reversed (ES vs. SE). Methods This cross-over study design included recreationally endurance trained men and women (age 21–45 years, n = 12 men n = 10 women) who performed both loadings. Maximal bilateral isometric strength (MVC), isometric rate of force development (RFD) and serum concentrations of testosterone (T), cortisol (C), growth hormone (GH), insulin-like growth factor 1 (IGF-1), binding protein 3 (IGFBP3) and sex hormone binding globulin (SHBG) were measured during and after both loadings. Results Both of the present combined (ES and SE) loadings led to a greater acute decrease in MVC in men than in women, while RFD was slightly affected only in men. Recovery of MVC and RFD to baseline was complete at 24 h regardless of the order of exercises. In men, neuromuscular fatigue was accompanied by increased C concentrations observed post SE. This was followed by decreased concentrations of T at 24 h and 48 h that were significantly lower than those observed following ES. GH response in men also differed significantly post loadings. In women, only a significant difference in T between ES and SE loadings was observed at post. Conclusion These observed differences in hormonal responses despite similarities in neuromuscular fatigue in men indicate the presence of an order effect as the body was not fully recovered at 48 h following SE. These findings may be applicable in training prescription in order to optimize specific training adaptations.peerReviewe

Angiotensin II inhibits insulin-stimulated GLUT4 translocation and Akt activation through tyrosine nitration-dependent mechanisms.

Angiotensin II (Ang II) plays a major role in the pathogenesis of insulin resistance and diabetes by inhibiting insulin's metabolic and potentiating its trophic effects. Whereas the precise mechanisms involved remain ill-defined, they appear to be associated with and dependent upon increased oxidative stress. We found Ang II to block insulin-dependent GLUT4 translocation in L6 myotubes in an NO- and O(2)(*-)-dependent fashion suggesting the involvement of peroxynitrite. This hypothesis was confirmed by the ability of Ang II to induce tyrosine nitration of the MAP kinases ERK1/2 and of protein kinase B/Akt (Akt). Tyrosine nitration of ERK1/2 was required for their phosphorylation on Thr and Tyr and their subsequent activation, whereas it completely inhibited Akt phosphorylation on Ser(473) and Thr(308) as well as its activity. The inhibitory effect of nitration on Akt activity was confirmed by the ability of SIN-1 to completely block GSK3alpha phosphorylation in vitro. Inhibition of nitric oxide synthase and NAD(P)Hoxidase and scavenging of free radicals with myricetin restored insulin-stimulated Akt phosphorylation and GLUT4 translocation in the presence of Ang II. Similar restoration was obtained by inhibiting the ERK activating kinase MEK, indicating that these kinases regulate Akt activation. We found a conserved nitration site of ERK1/2 to be located in their kinase domain on Tyr(156/139), close to their active site Asp(166/149), in agreement with a permissive function of nitration for their activation. Taken together, our data show that Ang II inhibits insulin-mediated GLUT4 translocation in this skeletal muscle model through at least two pathways: first through the transient activation of ERK1/2 which inhibit IRS-1/2 and second through a direct inhibitory nitration of Akt. These observations indicate that not only oxidative but also nitrative stress play a key role in the pathogenesis of insulin resistance. They underline the role of protein nitration as a major mechanism in the regulation of Ang II and insulin signaling pathways and more particularly as a key regulator of protein kinase activity.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Fitness, Diet and Coronary Risk Factors in a Sample of Southeastern U.S. Children.

The purpose of this study was to evaluate the relationship between physical fitness variables and nutrient intake to coronary risk factors (CRF) in a sample of children living in the Southeastern U.S. A total of 22 sixth-grade children of whom 10 were boys (mean age = 11.83 ± 0.3) and 12 were girls (mean age 11.7 ± 0.3) volunteered for this study. Results indicated that boys in comparison to girls weighed more (54.0 ± 10.8 kg versus 42.1 ± 8.0 kg; p<0.05), had a higher body mass index (BMI) (23.6 ± 2.7versus 20.2 ± 3.3; p<0.05), a higher lean body mass (37.8 ± 6.0 kg versus 30.7 ± 3.8 kg; p<0.01), and a higher systolic blood pressure (115.7 ± 11.1 versus 106.4 ± 8.1; p<.0001). There were, however, no significant gender differences in serum lipoproteins or nutrient intake. Stepwise multiple regression analyses indicated that physical fitness variables which included VO2max, one-mile run for time, grip strength, and leg strength could significantly predict resting diastolic blood pressure (DBP) (F=3.06; p<0.05) and percent body fat (F=4.98; p<0.01) in children. Analysis of food intake revealed that total and saturated fat, and carbohydrate intake could predict serum triglycerides (TG) (F=5.18; p=0.01) while total kilocalorie, fat, and carbohydrate intake could significantly predict percent body fat (F=3.42; p<0.03). These findings may be clinically relevant since both serum triglyceride levels and percent body fat were well above the 50th percentile according to U.S. norms. In summary, the present study showed that measurements of muscular strength in addition to aerobic fitness are associated with DBP and percent body fat in children. Furthermore, it is recommended that nutrient intake be used when evaluating CRF in children due to its ability to predict TG and percent body fat