Comparison of Physiological and Perceptual Responses to Upper-, Lower-, and Whole-Body Exercise in Elite Cross-Country Skiers.

Undebakke, V, Berg, J, Tjønna, AE, and Sandbakk, Ø. Comparison of physiological and perceptual responses to upper-, lower-, and whole-body exercise in elite cross-country skiers. J Strength Cond Res 33(4): 1086-1094, 2019-The primary purpose of the present study was to compare physiological and perceptual responses to maximal and submaximal exercise between upper-, lower-, and whole-body exercise modes in elite cross-country (XC) skiers. Twelve elite XC skiers performed 5-7 submaximal 5-minute stages and an incremental test to exhaustion using upper-body poling (UP), running (RUN), and diagonal skiing (DIA), randomized on 3 separate days. Here, power output, cardiorespiratory variables, heart rate (HR), blood lactate concentration (BLa), and rating of perceived exertion (RPE) were determined. Peak power output increased gradually from UP to RUN and DIA, whereas peak oxygen uptake (V[Combining Dot Above]O2peak), peak HR, O2pulse, and total RPE were clearly lower in UP than RUN and DIA (p < 0.05). At submaximal workloads matched for either RPE, %HR, or BLa, the main pattern was that BLa was higher and V[Combining Dot Above]O2 and HR lower in UP compared with RUN and DIA (p < 0.05). DIA showed ∼10 and 35% higher V[Combining Dot Above]O2 than RUN and UP at RPE 10-13 and had lower muscular RPE values than UP and RUN at a given % of peak HR (p < 0.05). Most of the differences in cardiorespiratory variables between modes were eliminated when they were normalized to V[Combining Dot Above]O2peak or peak HR in the respective mode. Because of the low power production in UP, endurance training in this mode exhibits too low values of V[Combining Dot Above]O2 to tax the cardiovascular system sufficiently. In RUN and DIA, the similar V[Combining Dot Above]O2peak values indicate that both modes can be effectively used during high-intensity training and to determine V[Combining Dot Above]O2max in elite XC skiers. However, the relatively high V[Combining Dot Above]O2 values at low perceptual stress with submaximal DIA indicate that the large amount of power produced when combining upper- and lower-body work exhibits high oxidative flux even during low-intensity training. Overall, these findings should be taken into account when athletes and coaches are monitoring and prescribing training in future approaches, in particular in sports where athletes vary between training with upper-, lower-, and whole-body exercise modes.

Assessment of the 5-Minute Oxygen Uptake Efficiency Slope in Children With Obesity.

PURPOSE: Poor cardiorespiratory fitness is associated with increased all cause morbidity and mortality. In children with obesity, maximum oxygen uptake (V̇O2max) may not be achieved due to reduced motivation and peripheral fatigue. We aimed to identify a valid submaximal surrogate for V̇O2max in children with obesity. METHOD: Ninety-two children with obesity (7-16 years) completed a maximal exercise treadmill test and entered a three-month exercise and/or nutrition intervention after which the exercise test was repeated (n = 63). Participants were required to reach V̇O2max to be included in this analysis (n = 32 at baseline and n = 13 at both time-points). The oxygen uptake efficiency slope (OUES) was determined as the slope of the line when V̇O2 (L/min) was plotted against log V̇E. Associations between the maximal OUES, submaximal OUES (at 3, 4, 5 and 6 min of the exercise test) and V̇O2max were calculated. RESULTS: In the cross-sectional analysis, V̇O2max (L/min) was strongly correlated with 5-min OUES independent of Tanner puberty stage and sex (R2 = .80, p < .001). Longitudinal changes in V̇O2max were closely reflected by changes in 5-min OUES independent of change in percent body fat (R2 = .63, p < .05). CONCLUSION: The 5-min OUES is a viable alternative to V̇O2max when assessing children with obesity.

Time course of endothelial adaptation after acute and chronic exercise in patients with metabolic syndrome.

Clustering of cardiovascular risk factors may lead to endothelial dysfunction. Physical exercise is an important factor in prevention and treatment of endothelial dysfunction. We wanted to determine the time course of adaptation to a single bout of exercise at either high or moderate intensity upon endothelial function both before and after a 16-week fitness program in patients with metabolic syndrome. Twenty-eight patients with metabolic syndrome participated in the study and were randomized and stratified (according to age and sex) into an aerobic interval exercise training group (AIT, n = 11), a continuously moderate-intensity exercise training group (CME, n = 8) or to a control group (n = 9). Flow-mediated dilatation (FMD) was determined at baseline, immediately, 24, 48, and 72 hours after 1 bout of exercise and repeated after 16 weeks of exercise. In the untrained state, FMD improved from 5 to 11% (p = 0.003) immediately after a single bout of aerobic interval training (AIT), an effect lasting 72 hours postexercise. In comparison, continuous moderate exercise (CME) improved FMD immediately after a single bout of exercise from 5 to 8% (p = 0.02), an effect lasting 24 hours postexercise (group difference, p < 0.001). In the trained state, a single bout of AIT resulted in a 2% (p = 0.007) acute increase of FMD lasting 48 hours postexercise. The CME increased FMD by 3% (p < 0.01), an effect lasting 24 hours postexercise (group difference p = 0.0012). Blood glucose level decreased after 1 single bout of AIT in the untrained state (p < 0.05), and the effect lasted at least 72 hours postexercise (p < 0.01). Acute CME decreased blood glucose with normalization of the values 24 hours postexercise (p < 0.01). A single bout of exercise in the trained state reduced fasting blood glucose by 10% (p < 0.05) after both AIT and CME. Exercise training, especially high intensity, thus appears to be highly beneficial in reducing blood glucose and improving endothelial function.

Aerobic interval training reduces cardiovascular risk factors more than a multitreatment approach in overweight adolescents.

The aim of the present study was to compare the effects of a multidisciplinary approach (MTG) and aerobic interval training (AIT) on cardiovascular risk factors in overweight adolescents. A total of 62 overweight and obese adolescents from Trøndelag County in Norway, referred to medical treatment at St Olav's Hospital, Trondheim, Norway, were invited to participate. Of these, 54 adolescents (age, 14.0 +/- 0.3 years) were randomized to either AIT (4 x 4 min intervals at 90% of maximal heart rate, each interval separated by 3 min at 70%, twice a week for 3 months) or to MTG (exercise, dietary and psychological advice, twice a month for 12 months). Follow-up testing occurred at 3 and 12 months. VO(2max) (maximal oxygen uptake) increased more after AIT compared with MTG, both at 3 months (11 compared with 0%; P<0.01) and 12 months (12 compared with -1%; P<0.01). AIT enhanced endothelial function compared with MTG at both 3 months (absolute change, 5.1 compared with 3.9%; P<0.01) and 12 months (absolute change, 6.3 compared with 1.0%; P<0.01). AIT was favourable compared with MTG in reducing BMI (body mass index), percentage of fat, MAP (mean arterial blood pressure) and increasing peak oxygen pulse. In addition, AIT induced a more favourable regulation of blood glucose and insulin compared with MTG. In conclusion, the novel findings of the present proof-of-concept study was that 3 months of twice weekly high-intensity exercise sessions reduced several known cardiovascular risk factors in obese adolescents more than that observed after a multitreatment strategy, which was initiated as hospital treatment. Follow-up at 12 months confirmed that AIT improved or maintained these risk factors to a better degree than MTG.

Transcriptional changes in blood after aerobic interval training in patients with the metabolic syndrome.

BACKGROUND: Regular physical activity has beneficial effects on the metabolic syndrome. Eleven metabolic syndrome patients performing 16 weeks of aerobic interval training, significantly reduced their risk of cardiovascular disease, in terms of improved VO2max, endothelial function, blood pressure, insulin signaling, and plasma lipid composition. The knowledge on underlying mechanism of exercise-induced improvements is sparse, and a broad spectrum of methods is needed to gain more insight. DESIGN: The aim was, for the first time, to determine whether transcriptional changes occur in blood cells of metabolic syndrome patients after participating in an exercise program. METHODS: Blood was collected in PAXgene and EDTA tubes before and after 16 weeks of exercise. RNA was extracted and run on microarrays. RESULTS: Eleven biological processes and molecular functions were upregulated after exercise, whereas seven were downregulated. Blood clotting, cell adhesion, and steroid metabolism were among the downregulated processes, whereas steroid hormone-mediated signaling was upregulated. Downregulated protein levels of arginase 1 and von Willebrand factor confirmed microarray results. CONCLUSION: Increased transcription of genes involved in steroid hormone-mediated signaling, decreased levels of arginase 1, and reduced transcription of genes involved in cell adhesion, and blood clotting are likely to be involved in exercise-induced improvements of endothelial function, and improved cardiovascular risk profile of metabolic syndrome patients. These findings have provided new insights on exercise-induced improvement of cardiovascular health.

Aerobic high intensity one and two legs interval cycling in chronic obstructive pulmonary disease: the sum of the parts is greater than the whole.

The purpose of this study was to investigate whether individual leg cycling could produce higher whole body peak oxygen uptake (VO(2peak)) than two legs cycling during aerobic high intensity interval training in chronic obstructive pulmonary disease (COPD) patients. Nineteen patients trained in 24 supervised cycling sessions either by one leg training (OLT) (n = 12) or by two legs training (TLT) (n = 7) at 4 x 4 min intervals at 85-95% of peak heart rate. Whole body VO(2peak) and peak work rate increased significantly by 12 and 23% in the OLT, and by 6 and 12% in the TLT from pre- to post-training, respectively, and were significantly greater in the OLT than the TLT (P < 0.05). The present study demonstrates that one leg aerobic high intensity interval cycling is superior to two legs in increasing whole body VO(2peak), indicating a muscle rather than a cardiovascular limitation to VO(2peak) in these COPD patients.

Both aerobic endurance and strength training programmes improve cardiovascular health in obese adults.

Regular exercise training is recognized as a powerful tool to improve work capacity, endothelial function and the cardiovascular risk profile in obesity, but it is unknown which of high-intensity aerobic exercise, moderate-intensity aerobic exercise or strength training is the optimal mode of exercise. In the present study, a total of 40 subjects were randomized to high-intensity interval aerobic training, continuous moderate-intensity aerobic training or maximal strength training programmes for 12 weeks, three times/week. The high-intensity group performed aerobic interval walking/running at 85-95% of maximal heart rate, whereas the moderate-intensity group exercised continuously at 60-70% of maximal heart rate; protocols were isocaloric. The strength training group performed 'high-intensity' leg press, abdominal and back strength training. Maximal oxygen uptake and endothelial function improved in all groups; the greatest improvement was observed after high-intensity training, and an equal improvement was observed after moderate-intensity aerobic training and strength training. High-intensity aerobic training and strength training were associated with increased PGC-1alpha (peroxisome-proliferator-activated receptor gamma co-activator 1alpha) levels and improved Ca(2+) transport in the skeletal muscle, whereas only strength training improved antioxidant status. Both strength training and moderate-intensity aerobic training decreased oxidized LDL (low-density lipoprotein) levels. Only aerobic training decreased body weight and diastolic blood pressure. In conclusion, high-intensity aerobic interval training was better than moderate-intensity aerobic training in improving aerobic work capacity and endothelial function. An important contribution towards improved aerobic work capacity, endothelial function and cardiovascular health originates from strength training, which may serve as a substitute when whole-body aerobic exercise is contra-indicated or difficult to perform.

Carbon monoxide levels experienced by heavy smokers impair aerobic capacity and cardiac contractility and induce pathological hypertrophy.

Cigarette smoke contains hundreds of potentially toxic compounds and is an important risk factor for cardiovascular disease. However, the key components responsible for endothelial and myocardial dysfunction have not been fully identified. The objective of the present study was to determine the cardiovascular effects of long-term inhalation of carbon monoxide (CO) administrated to give concentrations in the blood similar to those observed in heavy smokers. Female rats were exposed to either CO or air (control group) (n = 12). The CO group was exposed to 200 ppm CO (100 h/wk) for 18 mo. Rats exposed to CO had 24% lower maximal oxygen uptake, longer (145 vs. 123 microm) and wider (47 vs. 25 microm) cardiomyocytes, reduced cardiomyocyte fractional shortening (12 vs. 7%), and 26% longer time to 50% re-lengthening than controls. In addition, cardiomyocytes from CO-exposed rats had 48% lower intracellular calcium (Ca2 +) amplitude, 22% longer time to Ca2 + decay, 34% lower capacity of sarcoplasmic reticulum Ca2 +-ATPase (SERCA2a), and 37% less t-tubule area compared to controls. Phosphorylation levels of phospholamban at Ser16 and Thr17 were significantly reduced in the CO group, whereas total concentration of phospholamban and SERCA2a were unchanged. Cardiac atrial natriuretic peptide, vascular endothelial growth factor, cyclic guanosine monophosphate, calcineurin, calmodulin, pERK, and pS6 increased, whereas pAkt and pCaMKII delta remained unchanged by CO. Endothelial function and systemic blood pressure were not affected by CO exposure. Long-term CO exposure reduces aerobe capacity and contractile function and leads to pathological hypertrophy. Impaired Ca2 + handling and increased growth factor signaling seem to be responsible for these pathological changes.

Effect of High Intensity Interval Training on Cardiac Function in Children with Obesity: A Randomised Controlled Trial.

BACKGROUND: High intensity interval training (HIIT) confers superior cardiovascular health benefits to moderate intensity continuous training (MICT) in adults and may be efficacious for improving diminished cardiac function in obese children. The aim of this study was to compare the effects of HIIT, MICT and nutrition advice interventions on resting left ventricular (LV) peak systolic tissue velocity (S') in obese children. METHODS: Ninety-nine obese children were randomised into one of three 12-week interventions, 1) HIIT [n = 33, 4 × 4 min bouts at 85-95% maximum heart rate (HRmax), 3 times/week] and nutrition advice, 2) MICT [n = 32, 44 min at 60-70% HRmax, 3 times/week] and nutrition advice, and 3) nutrition advice only (nutrition) [n = 34]. RESULTS: Twelve weeks of HIIT and MICT were equally efficacious, but superior to nutrition, for normalising resting LV S' in children with obesity (estimated mean difference 1.0 cm/s, 95% confidence interval 0.5 to 1.6 cm/s, P < 0.001; estimated mean difference 0.7 cm/s, 95% confidence interval 0.2 to 1.3 cm/s, P = 0.010, respectively). CONCLUSIONS: Twelve weeks of HIIT and MICT were superior to nutrition advice only for improving resting LV systolic function in obese children.

Effect of High-Intensity Interval Training on Fitness, Fat Mass and Cardiometabolic Biomarkers in Children with Obesity: A Randomised Controlled Trial.

BACKGROUND: Paediatric obesity significantly increases the risk of developing cardiometabolic diseases across the lifespan. Increasing cardiorespiratory fitness (CRF) could mitigate this risk. High-intensity interval training (HIIT) improves CRF in clinical adult populations but the evidence in paediatric obesity is inconsistent. OBJECTIVES: The objectives of this study were to determine the efficacy of a 12-week, HIIT intervention for increasing CRF and reducing adiposity in children with obesity. METHODS: Children with obesity (n = 99, 7-16 years old) were randomised into a 12-week intervention as follows: (1) HIIT [n = 33, 4 × 4-min bouts at 85-95% maximum heart rate (HRmax), interspersed with 3 min of active recovery at 50-70% HRmax, 3 times/week] and nutrition advice; (2) moderate-intensity continuous training (MICT) [n = 32, 44 min at 60-70% HRmax, 3 times/week] and nutrition advice; and (3) nutrition advice only (nutrition) [n = 34]. CRF was quantified through a maximal exercise test ([Formula: see text]) while adiposity was assessed using magnetic resonance imaging (MRI), dual-energy X-ray absorptiometry (DXA) and air-displacement plethysmography. RESULTS: HIIT stimulated significant increases in relative [Formula: see text] compared with MICT (+3.6 mL/kg/min, 95% CI 1.1-6.0, P = 0.004) and the nutrition intervention (+5.4 mL/kg/min, 95% CI 2.9-7.9, P = 0.001). However, the intervention had no significant effect on visceral and subcutaneous adipose tissue, whole body composition or cardiometabolic biomarkers (P > 0.05). CONCLUSION: A 12-week, HIIT intervention was highly effective in increasing cardiorespiratory fitness when compared with MICT and nutrition interventions. While there were no concomitant reductions in adiposity or blood biomarkers, the cardiometabolic health benefit conferred through increased CRF should be noted. CLINICAL TRIALS REGISTRATION NUMBER: Clinicaltrials.gov; NCT01991106.

Evidence against a beneficial effect of irisin in humans.

Brown adipose tissue has gained interest as a potential target to treat obesity and metabolic diseases. Irisin is a newly identified hormone secreted from skeletal muscle enhancing browning of white fat cells, which improves systemic metabolism by increasing energy expenditure in mice. The discovery of irisin raised expectations of its therapeutic potential to treat metabolic diseases. However, the effect of irisin in humans is unclear. Analyses of genomic DNA, mRNA and expressed sequence tags revealed that FNDC5, the gene encoding the precursor of irisin, is present in rodents and most primates, but shows in humans a mutation in the conserved start codon ATG to ATA. HEK293 cells transfected with a human FNDC5 construct with ATA as start codon resulted in only 1% full-length protein compared to human FNDC5 with ATG. Additionally, in vitro contraction of primary human myotubes by electrical pulse stimulation induced a significant increase in PGC1α mRNA expression. However, FNDC5 mRNA level was not altered. FNDC5 mRNA expression in muscle biopsies from two different human exercise studies was not changed by endurance or strength training. Preadipocytes isolated from human subcutaneous adipose tissue exhibited differentiation to brite human adipocytes when incubated with bone morphogenetic protein (BMP) 7, but neither recombinant FNDC5 nor irisin were effective. In conclusion, our findings suggest that it is rather unlikely that the beneficial effect of irisin observed in mice can be translated to humans.