One-year aerobic interval training in outpatients with schizophrenia: A randomized controlled trial

Although aerobic interval training (AIT) is recognized to attenuate the risk of cardiovascular disease (CVD) and premature mortality, it appears that it rarely arrives at patients’ doorsteps. Thus, this study investigated 1-year effects and feasibility of AIT delivered with adherence support in collaborative care of outpatients with schizophrenia. Forty-eight outpatients (28 men, 35 [31-38] (mean [95% confidence intervals]) years; 20 women, 36 [30-41] years) with schizophrenia spectrum disorders (ICD-10) were randomized to either a collaborative care group provided with municipal transportation service and training supervision (walking/running 4 × 4 minutes at ~90% of peak heart rate; HR_peak) 2 d wk⁻¹ at the clinic (TG) or a control group (CG) given 2 introductory AIT sessions and advised to continue training. Directly assessed peak oxygen uptake () increased in the TG after 3 months (2.3 [0.6-4.4] mL kg⁻¹ min⁻¹, Cohen's d = 0.33[−4.63 to 4.30], P = 0.04), 6 months (2.7 [0.5-4.8] mL kg⁻¹ min⁻¹, Cohen's d = 0.42[−4.73 to 4.11], P = 0.02) and 1 year (4.6 [2.3-6.8] mL kg⁻¹ min⁻¹, Cohen's d = 0.70[−4.31 to 4.10], P < 0.001) compared to the CG. One-year cardiac effects revealed higher HR_peak (7 [2-11] b min⁻¹, Cohen's d = 0.34[−8.48 to 8.65], P = 0.01), while peak stroke volume tended to be higher (0.9 [−0.2 to 2.0] mL b⁻¹, Cohen's d = 0.35[−1.62 to 2.01], P = 0.11) in the TG compared to the CG. Conventional risk factors (body weight, waist circumference, blood pressure, and lipids/glucose) remained unaltered in both groups. One-year AIT adherence rates were 15/25 (TG; different from CG: P < 0.001) and 0/23 (CG). AIT was successfully included in long-term collaborative care of outpatients with schizophrenia and yielded improved , advocating this model for aerobic capacity improvement and CVD risk reduction in future treatment.     

Peak oxygen uptake cut‐points to identify children at increased cardiometabolic risk – The PANIC Study

We aimed to develop cut‐points for directly measured peak oxygen uptake () to identify boys and girls at increased cardiometabolic risk using different scaling methods to control for body size and composition. Altogether 352 children (186 boys, 166 girls) aged 9‐11 years were included in the analyses. We measured V?O_2peak directly during a maximal cycle ergometer exercise test and lean body mass (LM) by bioelectrical impedance. We computed a sex‐ and age‐specific cardiometabolic risk score (CRS) by summing important cardiometabolic risk factors and defined increased cardiometabolic risk as >1 standard deviation above the mean of CRS. Receiver operating characteristics curves were used to detect V?O_2peak cut‐points for increased cardiometabolic risk. Boys with V?O_2peak <45.8 mL kg body mass (BM)^?1 min^?1 (95% confidence interval [CI] = 45.1 to 54.6, area under the curve [AUC] = 0.86, P < 0.001) and <63.2 mL kg LM^?1 min^?1 (95% CI =52.4 to 67.5, AUC = 0.65, P = 0.006) had an increased CRS. Girls with V?O_2peak <44.1 mL kg BM^?1 min^?1 (95% CI = 44.0 to 58.6, AUC = 0.67, P = 0.013) had an increased CRS. V?O_2peak scaled by BM^?0.49 and LM^?0.77 derived from log‐linear allometric modeling poorly predicted increased cardiometabolic risk in boys and girls. In conclusion, directly measured <45.8 mL kg BM^?1 min^?1 among boys and <44.1 mL kg BM^?1 min^?1 among girls were cut‐points to identify those at increased cardiometabolic risk. Appropriately controlling for body size and composition reduced the ability of cardiorespiratory fitness to identify children at increased cardiometabolic risk.     

Superior performance improvements in elite cyclists following short-interval vs effort-matched long-interval training

The purpose of this study was to compare the effects of 3 weeks with three weekly sessions (ie, nine sessions in total) of short intervals (SI; n = 9; 3 series with 13 × 30-second work intervals interspersed with 15-second recovery and 3-minutes recovery between series) against effort-matched (rate of perceived effort based) long intervals (LI; n = 9; 4 series of 5-minute work intervals with 2.5-minutes recovery between series) on performance parameters in elite cyclists ( 73 ± 4 mL min⁻¹ kg⁻¹). There were no differences between groups in total volume and intensity distribution of training during the intervention period. SI achieved a larger (P < .05) relative improvement in peak aerobic power output than LI (3.7 ± 4.3% vs −0.3 ± 2.8%, respectively), fractional utilization of at 4 mmol L⁻¹ [La⁻] (3.0 ± 5.8 percent points vs −3.5 ± 2.7 percent points, respectively), and larger relative increase in power output at 4 mmol L⁻¹ [La⁻] (2.0 ± 6.7% vs −2.8 ± 3.4, respectively), while there was no group difference in change of . Improvements in performance measured as mean power output during 20-minute cycling test were greater (P < .01) in SI compared with LI (4.7 ± 4.4% vs −1.4 ± 2.2%, respectively). Mean effect size of the improvement in the above variables revealed a small to large effect of SI training vs LI training. The data thus demonstrate that the present SI protocol induces superior training adaptations compared with the present LI protocol in elite cyclists.     

Oxygen uptake plateau occurrence depends on oxygen kinetics and oxygen deficit accumulation

We tested the hypothesis that participants with an oxygen uptake () plateau during incremental exercise exhibit a lower VO₂‐deficit (VO_2DEF)‐accumulation in the submaximal intensity domain due to faster ramp and square wave O₂‐kinetics. Twenty‐six male participants performed a standard ramp test (increment: 30 W·min^?1), a ramp test with an individualized ramp slope and a two‐step (moderate and severe) square wave exercise followed by a ‐verification bout. VO_2DEF was calculated by the difference between individualized ramp test O₂ and O₂‐demand estimated from steady‐state O₂‐kinetics. Twenty‐four participants verified their O_2max in the verification test. Ten of them showed a plateau in the individualized ramp test. VO_2DEF at the end of this ramp test (4.34 ± 0.60 vs 4.54 ± 0.43 L) was not different between the plateau and the non‐plateau group (P > 0.05). The plateau group had a significantly (P < 0.05) lower VO_2DEF 2 minutes before termination of the individualized ramp test (2.24 ± 0.40 vs 2.78 ± 0.33 L). This coincided with a shorter mean response time (43 ± 9 vs 53 ± 7 seconds), a higher increase in O₂ per W (10.1 ± 0.2 vs 9.2 ± 0.5 mL·min^?1·W^?1) at the individualized ramp test as well as shorter time constants of moderate (36 ± 6 vs 48 ± 7 seconds) and severe (62 ± 9 vs 86 ± 10 seconds) square wave kinetics (all P < 0.05). We conclude that the O₂‐plateau occurrence requires a fast O₂‐kinetics and a low VO_2DEF‐accumulation at intensities below O_2max.     

Exercise training‐induced visceral fat loss in obese women: The role of training intensity and modality

Visceral fat loss in response to four‐cycle ergometer training regimens with explicit differences in exercise intensity and modality was compared. Fifty‐nine obese young women (body fat percentage ≥ 30%) were randomized to a 12‐week intervention consisting of either all‐out sprint interval training (SIT_all‐out, n = 11); supramaximal SIT (SIT₁₂₀, 120% O_2peak, n = 12); high‐intensity interval training (HIIT₉₀, 90% O_2peak, n = 12), moderate‐intensity continuous training (MICT, 60% O_2peak, n = 11), or no training (CON, n = 13). The total work done per training session in SIT₁₂₀, HIIT₉₀, and MICT was confined to 200 kJ, while it was deliberately lower in SIT_all‐out. The abdominal visceral fat area (AVFA) was measured through computed tomography scans. The whole‐body and regional fat mass were assessed through dual‐energy X‐ray absorptiometry. Pre‐, post‐, and 3‐hour post‐exercise serum growth hormone (GH), and epinephrine (EPI) were measured during selected training sessions. Following the intervention, similar reductions in whole‐body and regional fat mass were found in all intervention groups, while the reductions in AVFA resulting from SIT_all‐out, SIT₁₂₀, and HIIT₉₀ (>15 cm²) were greater in comparison with MICT (<3.5 cm², P < .05). The AVFA reductions among the SITs and HIIT groups were similar, and it was concomitant with the similar exercise‐induced releases of serum GH and EPI. CON variables were unchanged. These findings suggest that visceral fat loss induced by interval training at or above 90% O_2peak appeared unresponsive to the change in training intensity. Nonetheless, SIT_all‐out is still the most time‐efficient strategy among the four exercise‐training regimes for controlling visceral obesity.     

The relationship between peak fat oxidation and prolonged double-poling endurance exercise performance

The peak fat oxidation rate (PFO) and the exercise intensity that elicits PFO (Fat_max) are associated with endurance performance during exercise primarily involving lower body musculature, but it remains elusive whether these associations are present during predominant upper body exercise. The aim was to investigate the relationship between PFO and Fat_max determined during a graded exercise test on a ski-ergometer using double-poling (GET-DP) and performance in the long-distance cross-country skiing race, Vasaloppet. Forty-three healthy men completed GET-DP and Vasaloppet and were divided into two subgroups: recreational (RS, n = 35) and elite (ES, n = 8) skiers. Additionally, RS completed a cycle-ergometer GET (GET-Cycling) to elucidate whether the potential relationships were specific to exercise modality. PFO (r² = .10, P = .044) and Fat_max (r² = .26, P < .001) were correlated with performance; however, was the only independent predictor of performance (adj. R² = .36) across all participants. In ES, Fat_max was the only variable associated with performance (r² = .54, P = .038). Within RS, DP (r² = .11, P = .047) and ski-specific training background (r² = .30, P = .001) were associated with performance. Between the two GETs, Fat_max (r² = .20, P = .006) but not PFO (r² = .07, P = .135) was correlated. Independent of exercise mode, neither PFO nor Fat_max were associated with performance in RS (P > .05). These findings suggest that prolonged endurance performance is related to PFO and Fat_max but foremost to during predominant upper body exercise. Interestingly, Fat_max may be an important determinant of performance among ES. Among RS, DP , and skiing experience appeared as performance predictors. Additionally, whole-body fat oxidation seemed specifically coupled to exercise modality.     

Increased oxygen extraction and mitochondrial protein expression after small muscle mass endurance training

When exercising with a small muscle mass, the mass-specific O₂ delivery exceeds the muscle oxidative capacity resulting in a lower O₂ extraction compared with whole-body exercise. We elevated the muscle oxidative capacity and tested its impact on O₂ extraction during small muscle mass exercise. Nine individuals conducted six weeks of one-legged knee extension (1L-KE) endurance training. After training, the trained leg (TL) displayed 45% higher citrate synthase and COX-IV protein content in vastus lateralis and 15%-22% higher pulmonary oxygen uptake ( ) and peak power output ( ) during 1L-KE than the control leg (CON; all P < .05). Leg O₂ extraction (catheters) and blood flow (ultrasound Doppler) were measured while both legs exercised simultaneously during 2L-KE at the same submaximal power outputs (real-time feedback-controlled). TL displayed higher O₂ extraction than CON (main effect: 1.7 ± 1.6% points; P = .010; 40%-83% of ) with the largest between-leg difference at 83% of (O₂ extraction: 3.2 ± 2.2% points; arteriovenous O₂ difference: 7.1 ± 4.8 mL· L⁻¹; P < .001). At 83% of , muscle O₂ conductance (D_MO₂; Fick law of diffusion) and the equilibration index Y were higher in TL (P < .01), indicating reduced diffusion limitations. The between-leg difference in O₂ extraction correlated with the between-leg ratio of citrate synthase and COX-IV (r = .72-.73; P = .03), but not with the difference in the capillary-to-fiber ratio (P = .965). In conclusion, endurance training improves O₂ extraction during small muscle mass exercise by elevating the muscle oxidative capacity and the recruitment of D_MO_2, especially evident during high-intensity exercise exploiting a larger fraction of the muscle oxidative capacity.     

Which exercise prescriptions optimize V̇O2max during cancer treatment?—A systematic review and meta‐analysis

The aims of the present systematic review and meta‐analysis were to investigate the effect of exercise on maximal oxygen uptake () and to investigate whether exercise frequency, intensity, duration, and volume are associated with changes in among adult patients with cancer undergoing treatment. Medline and Embase through OvidSP were searched to identify randomized controlled trials. Two reviewers extracted data and assessed the risk of bias. The overall effect size and differences in effects for different intensities and frequencies were calculated on change scores and post‐intervention data, and the meta‐regression of exercise duration and volumes was analyzed using the Comprehensive Meta‐Analysis software. Fourteen randomized controlled trials were included in the systematic review, comprising 1332 patients with various cancer types receiving (neo‐)adjuvant chemo‐, radio‐, and/or hormone therapy. Exercise induced beneficial changes in compared to usual care (effect size = 0.46, 95% Confidence Interval = 0.23‐0.69). Longer session duration (P = 0.020), and weekly duration (P = 0.010), larger weekly volume (P < 0.001), and shorter intervention duration (P = 0.005) were significantly associated with more beneficial changes in . No differences in effects between subgroups with respect to frequency and intensity were found. In conclusion, exercise has beneficial effects on in patients with cancer undergoing (neo‐)adjuvant treatment. As interventions with larger exercise volumes and longer session durations resulted in larger beneficial changes in , exercise frequency, intensity, and duration should be considered carefully for sufficient exercise volume to induce changes in for this patient group.     

Menstrual and oral contraceptive cycle phases do not affect submaximal and maximal exercise responses

To examine whether the menstrual or monophasic oral contraceptive cycle phases affect submaximal (oxygen uptake (O₂) kinetics, maximal lactate steady-state (MLSS)) and maximal (O_2max, time-to-exhaustion (TTE)) responses to exercise in healthy, active women. During the mid-follicular or inactive-pill phase and the mid-luteal or active-pill phase of the respective menstrual or oral contraceptive cycle, 15 non-oral contraceptive users (mean and standard deviation (SD) (±): 27 ± 6 years; 171 ± 5 cm; 65 ± 7 kg) and 15 monophasic oral contraceptive users (24 ± 4 years; 169 ± 10 cm; 68 ± 10 kg) performed: one O₂ kinetics test; one ramp-incremental test; two to three 30-minute constant-load cycling trials to determine the power output corresponding to MLSS (MLSS_p), followed by a TTE trial. The phase of the menstrual or oral contraceptive cycle did not affect the time constant of the O₂ kinetics response (τO₂) (mid-follicular, 20 ± 5 seconds and mid-luteal, 18 ± 3 seconds; inactive-pill, 22 ± 8 seconds and active-pill, 23 ± 6 seconds), O_2max (mid-follicular, 3.06 ± 0.32 L min⁻¹ and mid-luteal, 3.00 ± 0.33 L min⁻¹; inactive-pill, 2.87 ± 0.39 L min⁻¹ and active-pill, 2.87 ± 0.45 L min⁻¹), MLSS_p (mid-follicular, 181 ± 30 W and mid-luteal, 182 ± 29 W; inactive-pill, 155 ± 26 W and active-pill, 155 ± 27 W), and TTE (mid-follicular, 147 ± 42 seconds and mid-luteal, 128 ± 54 seconds; inactive-pill, 146 ± 70 seconds and active-pill, 139 ± 77 seconds) (P > .05). The rate of perceived exertion (RPE) at minute 30 of the MLSS_p trials was greater in the mid-follicular phase (6.2 ± 1.5) compared with the mid-luteal phase (5.3 ± 1.4) for non-oral contraceptive users (P = .022). The hormonal fluctuations between the menstrual and oral contraceptive cycle phases had no detectable effects on submaximal and maximal exercise performance, even when RPE differed.     

Effect of beta2‐adrenergic agonist and resistance training on maximal oxygen uptake and muscle oxidative enzymes in men

While beta₂‐adrenoceptor stimulation has been shown to increase lean mass and to alter metabolic properties of skeletal muscle, adaptations in muscle oxidative enzymes and maximal oxygen uptake (O_2max) in response to beta₂‐adrenergic agonist treatment are inadequately explored in humans, particularly in association with resistance training. Herein, we investigated beta₂‐adrenergic‐induced changes in O_2max, leg and arm composition, and muscle content of oxidative enzymes in response to treatment with the selective beta₂‐adrenergic agonist terbutaline with and without concurrent resistance training in young men. Forty‐six subjects were randomized to 4 weeks of lifestyle maintenance (n = 23) or resistance training (n = 23). Within the lifestyle maintenance and resistance training group, subjects received daily terbutaline (8 × 0.5 mg) (n = 13) or placebo (n = 10) treatment. No apparent treatment by training interactions was observed during the study period. Terbutaline increased leg and arm lean mass with the intervention, whereas no treatment differences were observed in absolute O_2max and incremental peak power output (iPPO). Treatment main effects were observed for O₂‐reserve (P < .05), O_2max relative to body mass (P < .05), O_2max relative to leg lean mass (P < .01), and iPPO relative to leg lean mass, in which terbutaline had a negative effect compared with placebo. Furthermore, content of electron transport chain complex I‐V decreased by 11% (P < .05) for terbutaline compared with placebo. Accordingly, chronic treatment with the selective beta₂‐adrenergic agonist terbutaline may negatively affect O_2max and iPPO in relative terms, but not in absolute.     

Glucose response to exercise in the post‐prandial period is independent of exercise intensity

This study investigated the acute glucose response to low‐intensity, moderate‐intensity, and high‐intensity interval exercise compared to no‐exercise in healthy insufficiently active males using a four‐arm, randomized, crossover design. Ten males (age: 37.3 ± 7.3 years, BMI : 29.3 ± 6.5 kg·m⁻²) completed four 30‐minute interventions at weekly intervals comprising low‐intensity exercise (LIE ) at ~35% O₂R, moderate‐intensity exercise (MIE ) at ~50% O₂R, high‐intensity interval exercise (HIIE ) at ~80% O₂R, and a no‐exercise control. Participants performed cycle ergometer exercise 30 minutes after finishing breakfast. Glucose response was assessed using a continuous glucose monitor under free‐living conditions with dietary intake replicated. A significant effect for intensity on energy expenditure was identified (P  < .001) with similar energy cost in MIE (mean ± SD : 869 ± 148 kJ) and HIIE (806 ± 145 kJ ), which were both greater than LIE (633 ± 129 kJ). The pattern of glucose response between the interventions over time was different (P  = .02). Glucose was lower 25 minutes into each of the HIIE , MIE and LIE trials respectively (mean difference ± SD : −0.7 ± 1.1; −0.9 ± 1.1; −0.6 ± 0.9 mmol·L⁻¹; P  < .05) than in the no‐exercise trial. Glucose response was not different between exercise intensities (P  > .05). Twenty‐four‐hour AUC was not affected by exercise intensity (P  = .75). There was a significant effect for exercise enjoyment (P  = .02), with LIE (69 ± 4) preferred less than HIIE (mean ± SD : 84 ± 14; P  = .02), MIE (73 ± 5; P  = .03), and no‐exercise (75 ± 4; P  = .03). Exercise at any intensity 30 minutes after a meal affects glycemic regulation equally in insufficiently active males. Moderate to vigorous exercise intensities were preferred, and therefore, the exercise guidelines appear appropriate for the prevention of cardiometabolic disease.     

Physical capacity,not skeletal maturity,distinguishes competitive levels in male Norwegian U14 soccer players

The main aim of the present study was to compare skeletal maturity level and physical capacities between male Norwegian soccer players playing at elite, sub-elite and non-elite level. Secondary, we aimed to investigate the association between skeletal maturity level and physical capacities. One hundred and two U14 soccer players (12.8-14.5 years old) recruited from four local clubs, and a regional team were tested for bone age and physical capacities. Bone age was estimated with x-ray of their left hand and used to indicate maturation of the skeleton. Players went through a comprehensive test battery to assess their physical capacities. Between-groups analysis revealed no difference in chronological age, skeletal maturity level, leg strength, body weight, or stature. However, elite players were superior to sub-elite and non-elite players on important functional characteristics as intermittent-endurance capacity (running distance: 1664 m ± 367 vs 1197 m ± 338 vs 693 m ± 235) and running speed (fastest 10 m split time: 1.27 seconds ± 0.06 vs 1.33 seconds ± 0.10 vs 1.39 seconds ± 0.11), in addition to maximal oxygen uptake (), standing long jump, and upper body strength (P < .05 for all comparisons). Medium-to-large correlations were found between skeletal maturity level and peak force (r = 695, P < .01), power (r = 684, P < .01), sprint (r = −.471, P<.001), and jump performance (r = .359, P < .01), but no correlation with upper body strength, , or intermittent-endurance capacity. These findings imply that skeletal maturity level does not bias the selection of players, although well-developed physical capacity clearly distinguishes competitive levels. The superior physical performance of the highest-ranked players seems related to an appropriate training environment.     

Acute and sustained effects of a periodized carbohydrate intake using the sleep‐low model in endurance‐trained males

Repeated periodization of carbohydrate (CHO) intake using a diet‐exercise strategy called the sleep‐low model can potentially induce mitochondrial biogenesis and improve endurance performance in endurance‐trained individuals. However, more studies are needed to confirm the performance‐related effects and to investigate the sustained effects on maximal fat oxidation (MFO) rate and proteins involved in intramuscular lipid metabolism. Thirteen endurance‐trained males (age 23‐44 years; O₂‐max, 63.9 ± 4.6 mL·kg^?1·min^?1) were randomized into two groups: sleep‐low (LOW‐CHO) or high CHO availability (HIGH‐CHO) in three weekly training blocks over 4 weeks. The acute metabolic response was investigated during 60 minutes of exercise within the last 3 weeks of the intervention. Pre‐ and post‐intervention, 30‐minute time‐trial performance was investigated after a 90‐minute pre‐load, which as a novel approach included nine intense intervals (and estimation of MFO). Additionally, muscle biopsies (v. lateralis) were obtained to investigate expression of proteins involved in intramuscular lipid metabolism using Western blotting. During acute exercise, average fat oxidation rate was ~36% higher in LOW‐CHO compared to HIGH‐CHO (P = .03). This did not translate into sustained effects on MFO. Time‐trial performance increased equally in both groups (overall time effect: P = .005). We observed no effect on intramuscular proteins involved in lipolysis (ATGL, G0S2, CGI‐58, HSL) or fatty acid transport and β‐oxidation (CD‐36 and HAD, respectively). In conclusion, the sleep‐low model did not induce sustained effects on MFO, endurance performance, or proteins involved in intramuscular lipid metabolism when compared to HIGH‐CHO. Our study therefore questions the transferability of acute effects of the sleep‐low model to superior sustained adaptations.     

Merging self-reported with technically sensed data for tracking mobility behavior in a naturalistic intervention study. Insights from the GISMO study

Sound exposure data are central for any intervention study. In the case of utilitarian mobility, where studies cannot be conducted in controlled environments, exposure data are commonly self-reported. For short-term intervention studies, wearable devices with location sensors are increasingly employed. We aimed to combine self-reported and technically sensed mobility data, in order to provide more accurate and reliable exposure data for GISMO, a long-term intervention study. Through spatio-temporal data matching procedures, we are able to determine the amount of mobility for all modes at the best possible accuracy level. Self-reported data deviate ±10% from the corrected reference. Derived modal split statistics prove high compliance to the respective recommendations for the control group (CG) and the two intervention groups (IG-PT, IG-C). About 73.7% of total mileage was travelled by car in CG. This share was 10.3% (IG-PT) and 9.7% (IG-C), respectively, in the intervention groups. Commuting distances were comparable in CG and IG, but annual mean travel times differ between  = 8,458 min (σ = 6,427 min) for IG-PT,  = 8,444 min (σ = 5,961 min) for IG-C, and  = 5,223 min (σ = 5,463 min) for CG. Seasonal variabilities of modal split statistics were observable. However, in IG-PT and IG-C no shift toward the car occurred during winter months. Although no perfect single-method solution for acquiring exposure data in mobility-related, naturalistic intervention studies exists, we achieved substantially improved results by combining two data sources, based on spatio-temporal matching procedures.     

Sex differences in fitness and cardiac function during exercise in adolescents with chronic fatigue

Females demonstrate less robust Frank‐Starling mechanism with respect to cardiac preload than males at rest. We asked whether this phenomenon would also affect cardiac performance during exercise. We hypothesized that stroke volume (SV ) response to exercise would be more limited in deconditioned females such that cardiac output would be mainly rate dependent, compared with males. We conducted a chart audit of clinical exercise tests performed by adolescents with chronic fatigue. Oxygen uptake () was measured breath‐by‐breath at rest and during cycle ergometry, while cardiac output was measured by acetylene rebreathing at rest plus 2‐3 subthreshold workloads. SV response was analyzed in two ways: after normalization for body surface area (SV index, SVI ) and as percentage change from resting values. Among 304 adolescents (78% females) with chronic fatigue, 189 (80%) of 236 females and 52 (76%) of 68 males were deconditioned (peakO₂ <90% predicted). Heart rate trajectory during exercise was steeper for unfit than fit females, 70 vs 61 beat·min⁻¹ per L·min⁻¹ , (P =.003); but not for males, 47 vs 42 beat·min⁻¹ per L·min⁻¹ (P =.23). The highest measured SVI did not differ between unfit vs fit females (42.8 vs 41.5 mL·m⁻², P =.39) while fit males showed larger SV during exercise than their unfit peers (highest SVI 55.9 vs 48.0 mL·m⁻², P =.014). Both qualitative and quantitative sex differences exist in SV responses to exercise among chronically fatigued adolescents, suggesting volume loading may be more efficacious in girls.     

Regulation of bone blood flow in humans: The role of nitric oxide,prostaglandins, and adenosine

The mechanisms that regulate bone blood flow (BBF ) in humans are largely unknown. Animal studies suggest that nitric oxide (NO ) could be involved, and in this study, we investigated the effects of inhibition of nitric oxide synthase (NOS ) alone and in combination with inhibition of cyclooxygenase (COX ) enzyme, thus prostaglandin (PG ) synthesis on femoral bone marrow blood flow by positron emission tomography in healthy young men at rest and during one‐leg dynamic exercise. In an additional group of healthy men, the role of adenosine (ADO ) in the regulation of BBF during exercise was investigated by use of an adenosine receptor blocker (aminophylline). Inhibitors were directly infused into the femoral artery. Resting BBF was 1.1 ± 0.4 mL 100 g⁻¹min⁻¹ and increased to almost sixfold in response to exercise (6.3 ± 1.5 mL 100 g⁻¹ min⁻¹). Inhibition of NOS reduced BBF at rest to 0.7 ± 0.3 mL 100 g⁻¹ min⁻¹ (P  = .036), but did not affect BBF significantly during exercise (5.5 ± 1.4 mL 100 g⁻¹ min⁻¹, P  = .25). On the other hand, while combined NOS and COX inhibition did not cause any further reduction of blood flow at rest (0.6 ± 0.2 mL 100 g⁻¹min⁻¹), the combined blockade reduced BBF during exercise by ~21%, to 5.0 ± 1.8 mL 100 g⁻¹ min⁻¹ (P  = .014). Finally, the ADO inhibition during exercise reduced BBF from 5.5 ± 1.9 mL 100 g⁻¹ min⁻¹ to 4.6 ± 1.2 mL 100 g⁻¹ min⁻¹ (P  = .045). In conclusion, our results support the view that NO is involved in controlling bone marrow blood flow at rest, and NO , PG , and ADO play important roles in controlling human BBF during exercise.     

Effects of nitrate supplementation in trained and untrained muscle are modest with initial high plasma nitrite levels

Nitrate () supplementation resulting in higher plasma nitrite () is reported to lower resting mean arterial blood pressure (MAP) and oxygen uptake (VO₂) during submaximal exercise in non‐athletic populations, whereas effects in general are absent in endurance‐trained individuals. To test whether physiologic effects of supplementation depend on local muscular training status or cardiovascular fitness, male endurance‐trained cyclists (CYC, n=9, VO₂‐max: 64±3 mL/min/kg; mean±SD) and recreational active subjects serving as a control group (CON, n=8, 46±3 mL/min/kg), acutely consumed nitrate‐rich beetroot juice ([] ~9 mmol) (NIT) or placebo (PLA) with assessment of resting MAP and energy expenditure during moderate intensity (~50% VO₂‐max) and incremental leg cycling (LEG‐ex) and arm‐cranking exercise (ARM‐ex). NIT increased (P<.001) resting plasma by ~1200% relative to PLA. Plasma increased ~25% (P<.01) with a significant change only in CYC. LEG‐ex VO₂ (~2.60 L/min), ARM‐ex VO₂ (~1.14 L/min), and resting MAP (~87 mm Hg) remained unchanged for CYC, and similarly for CON, no changes were observed for LEG‐ex VO₂ (~2.03 L/min), ARM‐ex VO₂ (~1.06 L/min), or resting MAP (~85 mm Hg). VO₂‐max was not affected by supplementation, but incremental test peak power was higher (P<.05) in LEG‐ex for CYC in NIT relative to PLA (418±47 vs 407±46 W). In both CYC and CON, high initial baseline values and small increases in plasma after NIT may have lowered the effect of the intervention implying that muscular and cardiovascular training status is likely not the only factors that influence the physiologic effects of supplementation.     

Physiological strain to prolonged exercise bouts at the walk–run transition speeds depends on locomotion mode in healthy untrained men

This study compared the physiological strain induced by prolonged walking and running performed at the walk–run transition speed (WRTS) in healthy untrained men. Twenty volunteers (age: 28 ± 5.01 years; height: 174.0 ± 0.3 cm; body mass: 74.5 ± 0.6 kg) underwent the following: (a) ramp‐incremental maximal cardiopulmonary exercise test (CPET); (b) specific protocol to detect the WRTS; and (c) two 30‐min walking and running bouts at WRTS (mean ± SD: 6.9 ± 0.06 km/h). Expired gases were collected during exercise bouts via the metabolic cart. A significant effect of locomotion mode (F = 4.8, P < 0.001) was observed with running resulting in higher cardiorespiratory responses than walking at the WRTS (oxygen uptake: mean difference = 0.26 L/min; pulmonary ventilation: mean difference = 5.53 L/min; carbon dioxide output: mean difference = 0.32 L/min; heart rate: mean difference = 13 beats/min; total energy expenditure: mean difference = 59 kcal). The rating of perceived exertion was similar across locomotion modes (mean difference = 0.3; P = 0.490). In conclusion, running promoted greater cardiorespiratory responses than walking at the WRTS in untrained healthy men. These data might have practical impact on aerobic training performed at intensities corresponding to WRTS.     

Exercise performance increase in smokeless tobacco‐user athletes after overnight nicotine abstinence

The use of nicotine administered through smokeless tobacco (snus) has increased among athletes. The purpose of this study was to investigate the ergogenic effects of snus on aerobic performance during exercise until exhaustion in athletes after abstinence or satiety nicotine conditions. The study utilized a randomized, controlled, within‐subject design experiment. Sixteen male snus‐user athletes completed an exercise until exhaustion at a constant load of their 80% of (calculated by a maximal incremental test) in two separate sessions, corresponding to nicotine conditions: 12‐hour overnight abstinence and satiety. A portion of 1 g of snus (~8 mg/g of nicotine) was administered 25 minutes before each experimental test. In each session, time to exhaustion (TTE), global rating of perceived exertion, cardiovascular and metabolic responses, and muscle and cerebral oxygenation were measured. Nicotine and cotinine analysis confirmed session conditions (abstinence or satiety). Snus induced a significant increase (+13.1%) of TTE following abstinence (24.1 ± 10.7 minutes) compared to satiety condition (20.9 ± 8.0 minutes; P = 0.0131). The baseline values revealed that abstinence of snus induced significant increase in the oxygenation of the muscular tissues (+4%), in metabolic values and in cardiovascular parameters, when compared to satiety condition. Our results indicate an increase of exercise performance (+13.1% TTE) due to snus administration in an abstinence condition. Considering that twelve hours of abstinence from snus‐contained nicotine affected metabolic, cardiovascular and muscular tissue oxygenation, we suggest that snus administration at test time might relieve these withdrawal changes and yield an increase in time to exhaustion.     

Effects of reduced‐volume of sprint interval training and the time course of physiological and performance adaptations

This study sought to determine the time course of training adaptations to two different sprint interval training programmes with the same sprint: rest ratio (1:8) but different sprint duration. Nine participants (M: 7; F: 2) were assigned to 15‐second training group (15TG) consisting of 4‐6 × 15‐second sprints interspersed with 2‐minute recovery, whereas eight participants (M: 5; F: 3) were assigned to 30‐second training group (30TG) consisting of 4‐6 × 30 second sprints interspersed with 4‐minute recovery. Both groups performed their respective training twice per week over 9 weeks and changes in peak oxygen uptake () and time to exhaustion (TTE) were assessed every 3 weeks. Additional eight healthy active adults (M: 6; F: 2) completed the performance assessments 9 weeks apart without performing training (control group, CON). Following 9 weeks of training, both groups improved (15TG: 12.1%; 30TG: 12.8%, P<.05) and TTE (15TG: 16.2%; 30TG: 12.8%, P<.01) to a similar extent. However, while both groups showed the greatest gains in at 3 weeks (15TG: 16.6%; 30TG: 17.0%, P<.001), those in TTE were greatest at 9 weeks. CON did not change any of performance variables following 9 weeks. This study demonstrated that while the changes in cardiorespiratory function plateau within several weeks with sprint interval training, endurance capacity (TTE) is more sensitive to such training over a longer time frame in moderately‐trained individuals. Furthermore, a 50% reduction in sprint duration does not diminish overall training adaptations over 9 weeks.