Reduced physical activity level and cardiorespiratory fitness in children with chronic diseases.

We aimed to compare physical activity level and cardiorespiratory fitness in children with different chronic diseases, such as type 1 diabetes mellitus (T1DM), obesity (OB) and juvenile idiopathic arthritis (JIA), with healthy controls (HC). We performed a cross-sectional study including 209 children: OB: n = 45, T1DM: n = 48, JIA: n = 31, and HC: n = 85. Physical activity level was assessed by accelerometer and cardiorespiratory fitness by a treadmill test. ANOVA, linear regressions and Pearson correlations were used. Children with chronic diseases had reduced total daily physical activity counts (T1DM 497 +/- 54 cpm, p = 0.003; JIA 518 +/- 28, p < 0.001, OB 590 +/- 25, p = 0.003) and cardiorespiratory fitness (JIA 39.3 +/- 1.7, p = 0.001, OB 41.7 +/- 1.2, p = 0.020) compared to HC (668 +/- 35 cpm; 45.3 +/- 0.9 ml kg(-1) min(-1), respectively). Only 60.4% of HC, 51.6% of OB, 38.1% of JIA and 38.5% of T1DM children met the recommended daily 60 min of moderate-to-vigorous physical activity. Low cardiorespiratory fitness was associated with female gender and low daily PA. Children with chronic diseases had reduced physical activity and cardiorespiratory fitness. As the benefits of PA on health have been well demonstrated during growth, it should be encouraged in those children to prevent a reduction of cardiorespiratory fitness and the development of comorbidities.

Cardiorespiratory responses during running and sport-specific exercises in handball players

To determine whether a 4-a-side handball (HB) game is an appropriate aerobic stimulus to reach and potentially enhance maximal oxygen uptake (V O(2)max), and whether heart rate (HR) is a valid index of V O(2) during a handball game. Nine skilled players (21.0+/-2.9 yr) underwent a graded maximal aerobic test (GT) where V O(2)max and HR-V O(2) relationship were determined. V O(2), HR and blood lactate ([La](b)) were recorded during a 2 x 225 s (interspersed with 30s rest) 4-a-side handball game and were compared to those measured during an 480-s running intermittent exercise (IE). Mean V O(2) tended to be higher in handball compared to IE (93.9+/-8.5 vs. 87.6+/-7.4% O(2)max, p=0.06), whereas HR was similar (92.3+/-4.9 vs. 93.9+/-3.9% of the peak of HR, p=0.10). [La](b) was lower for handball than for IE (8.9+/-3.5 vs. 11.6+/-2.1 mmol l(-1), p=0.04). Time spent over 90% of V O(2)max was higher for handball than for IE (336.1+/-139.6s vs. 216.1+/-124.7s; p=0.03). The HR-V O(2) relationship during GT was high (r(2)=0.96, p<0.001) but estimated V O(2) from HR was lower to that measured (p=0.03) in handball, whereas there was no difference in IE. 4-a-side handball game can be used as a specific alternative to IE for enhancing aerobic fitness in handball players. Nevertheless, the accuracy of HR measures for estimating V O(2) during handball is poor.

Aerobic and functional capacities in a selected active population of European octogenarians

Master athletes are often considered to represent the ideal rate of decline of aerobic function; however, most of the studies interested in active elderly people are often limited to people younger than 75. We aimed to determine the physiological adaptations and aerobic fitness in a selected European population of active octogenarians during maximal and submaximal exercise tests. Aerobic capacity was measured during maximal incremental tests on treadmill (TR) and cycle-ergometer (CE) and functional capacity during a 6-minute walk test (6-MWT) in 17 subjects aged 81.2 +/- 0.8 years. Pulmonary gas exchange and heart rate (HR) were continuously measured during the different exercise tests. Maximal oxygen consumption (V.O (2max)) on TR and CE was significantly higher than predicted values (TR: 28.7 +/- 1.2 vs. 17 +/- 0.5 ml . kg (-1) . min (-1); CE: 23 +/- 1.2 vs. 16 +/- 0.6 ml . kg (-1) . min (-1) for measured and predicted values respectively). V.O (2max) and HR (max), as well as V.O (2) and HR at the ventilatory threshold (V.O (2)T (V.E) and HR T (V.E)) were significantly higher on TR than on CE (HR (max): 144 +/- 4 vs. 138 +/- 4 bpm; V.O (2)T (V.E): 22.5 +/- 0.8 vs. 17.7 +/- 0.9 ml . kg (-1) . min (-1) for TR and CE respectively). V.O (2)T (V.E) and HR T (V.E) on TR were equivalent to V.O (2) and HR measured during the 6-MWT. HR T (V.E) on TR and mean HR during the 6-MWT were strongly correlated (R = 0.82, p < 0.01). Maintenance of regular physical activity provides high aerobic fitness, in octogenarians, as was shown by the higher values of our subjects in comparison to predicted values. Moreover, the close relation between the intensity developed at T (V.E) on TR and 6-MWT could support the idea that a walk test is a submaximal test performed at high intensity that could provide a basis for exercise prescription in an individualized manner in active elderly people.

Does the mechanical work in running change during the VO2 slow component?

PURPOSE: The origin of the slow component is not fully understood. The mechanical hypothesis is one of the potential factors, because an increase in external mechanical work with fatigue was previously reported for a constant velocity run. The purpose of this study was to determine whether a change in mechanical work could occur during the development of the VO2 slow component under the effect of fatigue. METHODS: Twelve regional-level competitive runners performed a square-wave transition, corresponding to 95% of the speed associated with peak VO2 obtained during an incremental test. The VO2 response was fit with a classical model including two exponential functions. A specific treadmill with three-dimensional force transducers was used to measure the ground reaction force. Kinetic work (W(kin)), potential work (W(pot)), external work (W(ext)), and an index of internal work (W(int)) per unit of distance were quantified continuously. RESULTS: During the slow component of VO2, a significant increase in W (P< 0.01), no change in W, and a significant decrease in W and W index (P< 0.05, P< 0.001, respectively) were observed. CONCLUSION: The present study showed that the slow component of VO2 did not result partly from a change in mechanical work under the effect of fatigue. Nevertheless, the decrease in stride frequency (P< 0.001) and contact time (P< 0.001) suggested an alternative mechanical explanation. The slow component during running may be due to the cost of generating force or to alterations in the storage and recoil of elastic energy, and not to the external mechanical work.

Effects of two types of fatigue on the VO(2) slow component.

The aim of the study was to test the hypothesis of the involvement of type II fibres in the V.O (2) slow component phenomenon by using two prior fatiguing protocols on the knee extensor muscles. Nine subjects performed three constant-load cycling exercises at a work rate corresponding to 80 % of their V.O (2) max: (i) preceded by a 20-min fatiguing protocol using electromyostimulation (EMS), (ii) preceded by a 20-min fatiguing protocol using voluntary contractions (VOL), and (iii) without fatiguing protocol (NFP). Voluntary and evoked neuromuscular properties of the knee extensor muscles were tested before (PRE) and after (POST) the two fatiguing protocols. Results show a significant reduction in voluntary force after both fatiguing protocols (-19.9 % and -11.8 %, in EMS and VOL, respectively p<0.01). After EMS, this decrease was greater than after VOL (p<0.05) and was combined with a slackening of muscle contractile properties which was absent after VOL (p<0.05). Regarding the effects on oxygen uptake kinetics, the appearance of the slow component was delayed after EMS and its amplitude was lower than those obtained in VOL and NFP conditions (0.48+/-0.07 vs. 0.75+/-0.09 and 0.69+/-0.08 L . min (-1), respectively; p<0.05). It can thus be concluded that exercises dedicated to preferentially fatiguing type II fibres may alter V.O (2) kinetics.

Long-term outcomes of pandemic 2009 influenza A(H1N1)-associated severe ARDS.

BACKGROUND: No data on long-term outcomes of survivors of 2009 influenza A(H1N1) (A[H1N1])-associated ARDS are available. The objective of this study was to compare the 1-year outcomes of survivors of A(H1N1)-associated ARDS, according to use or no use of extracorporeal lung assist (ECLA), using its need as an ARDS severity surrogate. METHODS: Survivors of ARDS (12 with ECLA use vs 25 without, corresponding to 75% and 54% of the eligible patients for each group, respectively) selected from the Réseau Européen de Ventilation Artificielle (REVA) registry had previously been healthy, with only pregnancy and/or moderate obesity (BMI ≤ 35 kg/m²) as known risk factors for A(H1N1) infection. Lung function and morphology, health-related quality of life (HRQoL), and psychologic impairment were evaluated. RESULTS: At 1 year post-ICU discharge for the ECLA and no-ECLA groups, respectively, 50% and 40% reported significant exertion dyspnea, 83% and 64% had returned to work, and 75% and 64% had decreased diffusion capacity across the blood-gas barrier, despite their near-normal and similar lung function test results. For both groups, exercise test results showed diminished but comparable exercise capacities, with similar alveolar-arterial oxygen gradients at peak exercise, and CT scans showed minor abnormal findings. HRQoL assessed by the 36-Item Short-Form Health Survey was poorer for both groups than for a sex- and age-matched general population group, but without between-group differences. ECLA and no-ECLA group patients, respectively, had symptoms of anxiety (50% and 56%) and depression (28% and 28%) and were at risk for posttraumatic stress disorder (41% and 44%). CONCLUSIONS: One year post-ICU discharge, a majority of survivors of A(H1N1)-associated ARDS had minor lung disabilities with diminished diffusion capacities across the blood-gas barrier, and most had psychologic impairment and poorer HRQoL than a sex- and age-matched general population group. ECLA and no-ECLA group patients had comparable outcomes. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT01271842; URL: www.clinicaltrials.gov

Acute supra-therapeutic oral terbutaline administration has no ergogenic effect in non-asthmatic athletes.

This study aimed to investigate the effects on a possible improvement in aerobic and anaerobic performance of oral terbutaline (TER) at a supra-therapeutic dose in 7 healthy competitive male athletes. On day 1, ventilatory threshold, maximum oxygen uptake [Formula: see text] and corresponding power output were measured and used to determine the exercise load on days 2 and 3. On days 2 and 3, 8 mg of TER or placebo were orally administered in a double-blind process to athletes who rested for 3 h, and then performed a battery of tests including a force-velocity exercise test, running sprint and a maximal endurance cycling test at Δ50 % (50 % between VT and [Formula: see text]). Lactatemia, anaerobic parameters and endurance performance ([Formula: see text] and time until exhaustion) were raised during the corresponding tests. We found that TER administration did not improve any of the parameters of aerobic performance (p > 0.05). In addition, no change in [Formula: see text] kinetic parameters was found with TER compared to placebo (p > 0.05). Moreover, no enhancement of the force-velocity relationship was observed during sprint exercises after TER intake (p > 0.05) and, on the contrary, maximal strength decreased significantly after TER intake (p < 0.05) but maximal power remained unchanged (p > 0.05). In conclusion, oral acute administration of TER at a supra-therapeutic dose seems to be without any relevant ergogenic effect on anaerobic and aerobic performances in healthy athletes. However, all participants experienced adverse side effects such as tremors.

Combined effects of endurance training and dietary unsaturated fatty acids on physical performance, fat oxidation and insulin sensitivity.

Endurance training improves exercise performance and insulin sensitivity, and these effects may be in part mediated by an enhanced fat oxidation. Since n-3 and n-9 unsaturated fatty acids may also increase fat oxidation, we hypothesised that a diet enriched in these fatty acids may enhance the effects of endurance training on exercise performance, insulin sensitivity and fat oxidation. To assess this hypothesis, sixteen normal-weight sedentary male subjects were randomly assigned to an isoenergetic diet enriched with fish and olive oils (unsaturated fatty acid group (UFA): 52 % carbohydrates, 34 % fat (12 % SFA, 12 % MUFA, 5 % PUFA), 14 % protein), or a control diet (control group (CON): 62 % carbohydrates, 24 % fat (12 % SFA, 6 % MUFA, 2 % PUFA), 14 % protein) and underwent a 10 d gradual endurance training protocol. Exercise performance was evaluated by measuring VO2max and the time to exhaustion during a cycling exercise at 80 % VO2max; glucose homeostasis was assessed after ingestion of a test meal. Fat oxidation was assessed by indirect calorimetry at rest and during an exercise at 50 % VO2max. Training significantly increased time to exhaustion, but not VO2max, and lowered incremental insulin area under the curve after the test meal, indicating improved insulin sensitivity. Those effects were, however, of similar magnitude in UFA and CON. Fat oxidation tended to increase in UFA, but not in CON. This difference was, however, not significant. It is concluded that a diet enriched with fish- and olive oil does not substantially enhance the effects of a short-term endurance training protocol in healthy young subjects.

Measurement of 13CO2 in expired air as an index of compliance to a high carbohydrate diet naturally enriched in 13C.

The aim of this study was to determine whether breath 13CO2 measurements could be used to assess the compliance to a diet containing carbohydrates naturally enriched in 13C. The study was divided into two periods: Period 1 (baseline of 4 days) with low 13C/12C ratio carbohydrates. Period 2 (5 days) isocaloric diet with a high 13C/12C ratio (corn, cane sugar, pineapple, millet) carbohydrates. Measurements were made of respiratory gas exchange by indirect calorimetry, urinary nitrogen excretion and breath 13CO2 every morning in post-absorptive conditions, both in resting state and during a 45-min low intensity exercise (walking on a treadmill). The subjects were 10 healthy lean women (BMI 20.4 +/- 1.7 kg/m2, % body fat 24.4 +/- 1.3%), the 13C enrichment of oxidized carbohydrate and breath 13CO2 were compared to the enrichment of exogenous dietary carbohydrates. At rest the enrichment of oxidized carbohydrate increased significantly after one day of 13C carbohydrate enriched diet and reached a steady value (103 +/- 16%) similar to the enrichment of exogenous carbohydrates. During exercise, the 13C enrichment of oxidized carbohydrate remained significantly lower (68 +/- 17%) than that of dietary carbohydrates. The compliance to a diet with a high content of carbohydrates naturally enriched in 13C may be assessed from the measurement of breath 13CO2 enrichment combined with respiratory gas exchange in resting, postabsorptive conditions.

Effects of flecainide on exercise-induced ventricular arrhythmias and recurrences in genotype-negative patients with catecholaminergic polymorphic ventricular tachycardia.

BACKGROUND: Conventional therapy with beta-blockers is incompletely effective in preventing arrhythmic events in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT). We have previously discovered that flecainide in addition to conventional drug therapy prevents ventricular arrhythmias in patients with genotype-positive CPVT. OBJECTIVE: To study the efficacy of flecainide in patients with genotype-negative CPVT. METHODS: We studied the efficacy of flecainide for reducing ventricular arrhythmias during exercise testing and preventing arrhythmia events during long-term follow-up. RESULTS: Twelve patients with genotype-negative CPVT were treated with flecainide. Conventional therapy failed to control ventricular arrhythmias in all patients. Flecainide was initiated because of significant ventricular arrhythmias (n = 8), syncope (n = 3), or cardiac arrest (n = 1). At the baseline exercise test before flecainide, 6 patients had ventricular tachycardia and 5 patients had bigeminal or frequent ventricular premature beats. Flecainide reduced ventricular arrhythmias at the exercise test in 8 patients compared to conventional therapy, similar to that in patients with genotype-positive CPVT in our previous report. Notably, flecainide completely prevented ventricular arrhythmias in 7 patients. Flecainide was continued in all patients except for one who had ventricular tachycardia at the exercise test on flecainide. During a follow-up of 48±94 months, arrhythmia events (sudden cardiac death and aborted cardiac arrest) associated with noncompliance occurred in 2 patients. Flecainide was not discontinued owing to side effects in any of the patients. CONCLUSIONS: Flecainide was effective in patients with genotype-negative CPVT, suggesting that spontaneous Ca(2+) release from ryanodine channels plays a role in arrhythmia susceptibility, similar to that in patients with genotype-positive CPVT.

Physiological differences between cycling and running: lessons from triathletes

The purpose of this review was to provide a synopsis of the literature concerning the physiological differences between cycling and running. By comparing physiological variables such as maximal oxygen consumption (V O(2max)), anaerobic threshold (AT), heart rate, economy or delta efficiency measured in cycling and running in triathletes, runners or cyclists, this review aims to identify the effects of exercise modality on the underlying mechanisms (ventilatory responses, blood flow, muscle oxidative capacity, peripheral innervation and neuromuscular fatigue) of adaptation. The majority of studies indicate that runners achieve a higher V O(2max) on treadmill whereas cyclists can achieve a V O(2max) value in cycle ergometry similar to that in treadmill running. Hence, V O(2max) is specific to the exercise modality. In addition, the muscles adapt specifically to a given exercise task over a period of time, resulting in an improvement in submaximal physiological variables such as the ventilatory threshold, in some cases without a change in V O(2max). However, this effect is probably larger in cycling than in running. At the same time, skill influencing motor unit recruitment patterns is an important influence on the anaerobic threshold in cycling. Furthermore, it is likely that there is more physiological training transfer from running to cycling than vice versa. In triathletes, there is generally no difference in V O(2max) measured in cycle ergometry and treadmill running. The data concerning the anaerobic threshold in cycling and running in triathletes are conflicting. This is likely to be due to a combination of actual training load and prior training history in each discipline. The mechanisms surrounding the differences in the AT together with V O(2max) in cycling and running are not largely understood but are probably due to the relative adaptation of cardiac output influencing V O(2max) and also the recruitment of muscle mass in combination with the oxidative capacity of this mass influencing the AT. Several other physiological differences between cycling and running are addressed: heart rate is different between the two activities both for maximal and submaximal intensities. The delta efficiency is higher in running. Ventilation is more impaired in cycling than in running. It has also been shown that pedalling cadence affects the metabolic responses during cycling but also during a subsequent running bout. However, the optimal cadence is still debated. Central fatigue and decrease in maximal strength are more important after prolonged exercise in running than in cycling.

Effects of Intermittent Training on Anaerobic Performance and MCT Transporters in Athletes.

This study examined the effects of intermittent hypoxic training (IHT) on skeletal muscle monocarboxylate lactate transporter (MCT) expression and anaerobic performance in trained athletes. Cyclists were assigned to two interventions, either normoxic (N; n = 8; 150 mmHg PIO2) or hypoxic (H; n = 10; ∼3000 m, 100 mmHg PIO2) over a three week training (5×1 h-1h30.week-1) period. Prior to and after training, an incremental exercise test to exhaustion (EXT) was performed in normoxia together with a 2 min time trial (TT). Biopsy samples from the vastus lateralis were analyzed for MCT1 and MCT4 using immuno-blotting techniques. The peak power output (PPO) increased (p<0.05) after training (7.2% and 6.6% for N and H, respectively), but VO2max showed no significant change. The average power output in the TT improved significantly (7.3% and 6.4% for N and H, respectively). No differences were found in MCT1 and MCT4 protein content, before and after the training in either the N or H group. These results indicate there are no additional benefits of IHT when compared to similar normoxic training. Hence, the addition of the hypoxic stimulus on anaerobic performance or MCT expression after a three-week training period is ineffective.

Daily physical activity assessment: what is the importance of upper limb movements vs whole body movements?

OBJECTIVE: The movement of the upper limbs (eg fidgeting-like activities) is a meaningful component of nonexercise activity thermogenesis (NEAT). This study examined the relationship between upper limb movements and whole body trunk movements, by simultaneously measuring energy expenditure during the course of the day. DESIGN: A cross-sectional study consisting of 88 subjects with a wide range in body mass index (17.3-32.5 kg/m(2)). The energy expenditure over a 24-h period was measured in a large respiratory chamber. The body movements were assessed by two uniaxial-accelerometers during daytime, one on the waist and the other on the dominant arm. The accelerometry scores from level 0 (=immobile) up to level 9 (=maximal intensity) were recorded. The activities of subjects were classified into eight categories: walking at two speeds on a horizontal treadmill (A & B), ambling (C), self-care tasks (D), desk work (E), meals (F), reading (G), watching TV (H). RESULTS: There was a significant relationship between the accelerometry scores from the waist (ACwaist) and that from the wrist (ACwrist) over the daytime period (R(2)=0.64; P<0.001). The ACwrist was systematically higher than the ACwaist during sedentary activities, whereas it was the reverse for walking activities. ACwrist to ACwaist ratio of activities E-H were above 1.0 and for walking activities (A-C) were below 1.0. A multiple regression analysis for predicting daytime energy expenditure revealed that the explained variance improved by 2% only when the ACwrist was added as a second predictor in addition to the ACwaist. This indicates that the effect of the ACwrist for predicting energy expenditure was of limited importance in our conditions of measurement. CONCLUSIONS: The acceleration of the upper limbs which includes fidgeting is more elevated than that of the whole body for sitting/lying down activities. However, their contribution to energy expenditure is lower than whole body trunk movements, thus indicating that the weight-bearing locomotion activities may be a key component of NEAT. However, its contribution may depend on the total duration of the upper limb movements during the course of the day.

Moderate exercise blunts oxidative stress induced by normobaric hypoxic confinement

PURPOSE: Both acute hypoxia and physical exercise are known to increase oxidative stress. This randomized prospective trial investigated whether the addition of moderate exercise can alter oxidative stress induced by continuous hypoxic exposure. METHODS: Fourteen male participants were confined to 10-d continuous normobaric hypoxia (FIO2 = 0.139 +/- 0.003, PIO2 = 88.2 +/- 0.6 mm Hg, approximately 4000-m simulated altitude) either with (HCE, n = 8, two training sessions per day at 50% of hypoxic maximal aerobic power) or without exercise (HCS, n = 6). Plasma levels of oxidative stress markers (advanced oxidation protein products [AOPP], nitrotyrosine, and malondialdehyde), antioxidant markers (ferric-reducing antioxidant power, superoxide dismutase, glutathione peroxidase, and catalase), nitric oxide end-products, and erythropoietin were measured before the exposure (Pre), after the first 24 h of exposure (D1), after the exposure (Post) and after the 24-h reoxygenation (Post + 1). In addition, graded exercise test in hypoxia was performed before and after the protocol. RESULTS: Maximal aerobic power increased after the protocol in HCE only (+6.8%, P < 0.05). Compared with baseline, AOPP was higher at Post + 1 (+28%, P < 0.05) and nitrotyrosine at Post (+81%, P < 0.05) in HCS only. Superoxide dismutase (+30%, P < 0.05) and catalase (+53%, P < 0.05) increased at Post in HCE only. Higher levels of ferric-reducing antioxidant power (+41%, P < 0.05) at Post and lower levels of AOPP (-47%, P < 0.01) at Post + 1 were measured in HCE versus HCS. Glutathione peroxidase (+31%, P < 0.01) increased in both groups at Post + 1. Similar erythropoietin kinetics was noted in both groups with an increase at D1 (+143%, P < 0.01), a return to baseline at Post, and a decrease at Post + 1 (-56%, P < 0.05). CONCLUSIONS: These data provide evidence that 2 h of moderate daily exercise training can attenuate the oxidative stress induced by continuous hypoxic exposure.

Energy expenditure during walking and running in obese and nonobese prepubertal children.

We measured body composition and energy expenditure during walking and running on a treadmill in 40 prepubertal children: 23 obese children (9.3 +/- 1.1 years of age; 46 +/- 10 kg (mean +/- SD)) and 17 nonobese matched control children (9.2 +/- 0.6 years of age; 30 +/- 5 kg). Energy expenditure was assessed by indirect calorimetry with a standard open-circuit method. At the same speed of exercise, the energy expenditure was significantly (p < 0.01) greater in obese than in control children, in both boys and girls. Expressed per kilogram of body weight or per kilogram of fat-free mass, the energy expenditure was comparable in the two groups. Obese children had a significantly (p < 0.01) larger pulmonary ventilatory response to exercise than did control children. Heart rate was comparable in boys and girls combined but significantly higher (p < 0.05) in obese subjects, if boys and girls were analyzed separately. These data indicate that walking and running are energetically more expensive for obese children than for children of normal body weight. The knowledge of these energy costs could be useful in devising a physical activity program to be used in the treatment of obese children.