One bout of vibration exercise with vascular occlusion activates satellite cells.

NEW FINDINGS: What is the central question of this study? Acute skeletal muscle satellite cell (SC) activation is associated with skeletal muscle hypertrophy. Although the quantity of SCs has been reported to increase following a single bout of resistance exercise, data on muscle fibre type-specific SC quantity and/or activation status after a single bout of vibration is presently lacking. What is the main finding and its importance? By determining SCs from muscle biopsies of the vastus lateralis using immunohistochemistry, we conclude that modification of vibration exercise by superimposition of occlusion induced activation and differentiation of SCs in young men, which had not been observed with whole-body vibration or blood flow restriction alone. We tested the hypothesis that whole-body vibration (WBV) is insufficient to expand satellite cell numbers 24 h postexercise, whereas WBV in combination with blood flow restriction (BFR) is sufficient. Twenty-five young men were randomly assigned to one of the following three groups: WBV, BFR exercise or WBVBFR. Satellite cell numbers were determined from muscle biopsies of the vastus lateralis muscle using immunohistochemistry. Satellite cell quantity and frequency (+99.4%, P = 0.012 and +77.1%, P = 0.010, respectively) increased only in the WBVBFR group. Similar results were obtained for the quantity and frequency of myogenin-positive myonuclei (+139.0%, P < 0.001 and +148.4%, P < 0.001, respectively). We conclude that modification of WBV by superimposition of BFR induced activation and differentiation of satellite cells in young men, which had not been observed with WBV or BFR alone. These data suggest that WBVBFR might represent a novel viable anabolic stimulus.

RhEPO improves time to exhaustion by non-hematopoietic factors in humans.

PURPOSE: Erythropoietin (EPO) controls red cell volume (RCV) and plasma volume (PV). Therefore, injecting recombinant human EPO (rhEPO) increases RCV and most likely reduces PV. RhEPO-induced endurance improvements are explained by an increase in blood oxygen (O2) transport capacity, which increases maximum O2 uptake ([Formula: see text]O2max). However, it is debatable whether increased RCV or [Formula: see text]O2max are the main reasons for the prolongation of the time to exhaustion (t lim) at submaximal intensity. We hypothesized that high rhEPO doses in particular contracts PV such that the improvement in t lim is not as strong as at lower doses while [Formula: see text]O2max increases in a dose-dependent manner. METHODS: We investigated the effects of different doses of rhEPO given during 4 weeks [placebo (P), low (L), medium (M), and high (H) dosage] on RCV, PV, [Formula: see text]O2max and t lim in 40 subjects. RESULTS: While RCV increased in a dose-dependent manner, PV decreased independent of the rhEPO dose. The improvements in t lim (P +21.4 ± 23.8%; L +16.7 ± 29.8%; M +44.8 ± 62.7%; H +69.7 ± 73.4%) depended on the applied doses (R (2) = 0.89) and clearly exceeded the dose-independent [Formula: see text]O2max increases (P -1.7 ± 3.2%; L +2.6 ± 6.8%; M +5.7 ± 5.1 %; H +5.6 ± 4.3 %) after 4 weeks of rhEPO administration. Furthermore, the absolute t lim was not related (R (2) ≈ 0) to RCV or to [Formula: see text]O2max. CONCLUSIONS: We conclude that a contraction in PV does not negatively affect t lim and that rhEPO improves t lim by additional, non-hematopoietic factors.

High-load resistance exercise with superimposed vibration and vascular occlusion increases critical power, capillaries and lean mass in endurance-trained men.

PURPOSE: It is a widely accepted premise in the scientific community and by athletes alike, that adding resistance exercise to a regular regimen of endurance training increases endurance performance in endurance-trained men. However, critical power (CP), capillarization, and myofiber size remain unaffected by this addition. Therefore, we tested whether the superimposition of resistance exercise with whole-body vibration and vascular occlusion (vibroX) would improve these variables in endurance-trained males relative to resistance exercise alone. METHODS: Twenty-one young, endurance-trained males were randomly assigned either to a vibroX (n = 11) or resistance (n = 10) training group. Both groups trained in a progressive mode twice a week for 8 weeks. Pre and post training, histochemical muscle characteristics, thigh muscle size, endurance and strength parameters were determined. RESULTS: vibroX increased CP (P = 0.001), overall capillary-to-fiber ratio (P = 0.001) and thigh lean mass (P < 0.001), while these parameters were unaffected by resistance training. The gain in CP by vibroX was positively correlated with the gain in capillarization (R(2) = 0.605, P = 0.008), and the gain in thigh lean mass was paralleled by increases in MyHC-1 and MyHC-2 fiber cross-sectional areas and strength. Maximum voluntary torque and the finite work capacity above CP (W') increased significantly only following resistance training. CONCLUSIONS: We achieved a proof of concept by demonstrating that modification of resistance exercise by superimposing side-alternating whole-body vibration and sustained vascular occlusion induced further improvements in CP, capillarization and hypertrophy, all of which were not observed with resistance training alone.

Optimised heart rate formulae to monitor endurance training in sedentary individuals.

The aim of this study was to assess the validity of the heart rate formula 170 - 0.5 age ± 10 used to prescribe endurance training for healthy sedentary or moderately trained individuals. A total of 795 incremental tests of women and men during running and cycling were analysed. The maximum heart rate, heart rate at deflection and age-dependent declines of these heart rates were determined. The maximum heart rate and the heart rate at deflection were greater during running (women: 192 ± 10 and 181 ± 9 bpm; men: 191 ± 10 and 179 ± 10 bpm) than cycling (women: 185 ± 11 and 170 ± 11 bpm; men: 187 ± 10 and 169 ± 11 bpm, P < 0.001) without any sex-based difference. With the upper limit of the existing heart rate formula, 4% during running and 35% during cycling exceeded the heart rate at deflection. We suggest two heart rate formulae for healthy sedentary or moderately endurance trained individuals separated for mode of exercise but not for sex: 165 - 0.5 age ± 5 for running and 160 - 0.5 age ± 5 for cycling.

Combined whole-body vibration, resistance exercise, and sustained vascular occlusion increases PGC-1α and VEGF mRNA abundances.

We previously reported that high load resistance exercise with superimposed whole-body vibration and sustained vascular occlusion (vibroX) markedly improves cycling endurance capacity, increases capillary-to-fibre ratio and skeletal muscle oxidative enzyme activity in untrained young women. These findings are intriguing, since increases in oxidative muscle phenotype and endurance capacity are typically induced by endurance but not heavy resistance exercise. Here, we tested the hypothesis that vibroX activates genes associated with mitochondrial biogenesis and angiogenesis. Eight healthy, recreationally resistance-trained young men performed either vibroX or resistance exercise (RES) in a randomised, cross-over design. Needle biopsies (M. vastus lateralis) were obtained at rest and 3 h post-exercise. Changes in relative gene expression levels were assessed by real-time quantitative PCR. After vibroX, vascular endothelial growth factor and peroxisome proliferator-activated receptor-γ coactivator 1α mRNA abundances increased to 2- and 4.4-fold, respectively, but did not significantly change above resting values after RES. Other genes involved in mitochondrial biogenesis were not affected by either exercise modality. While vibroX increased the expression of hexokinase II, xanthine dehydrogenase, and manganese superoxide dismutase mRNA, there were no changes in these transcripts after RES. This study demonstrates that high load resistance exercise with superimposed whole-body vibration and sustained vascular occlusion activates metabolic and angiogenic gene programs, which are usually activated after endurance but not resistance exercise. Thus, targeted modification of high load resistance exercise by vibration and vascular occlusion might represent a novel strategy to induce endurance-type muscle adaptations.

Fatigue-induced increase in intracortical communication between mid/anterior insular and motor cortex during cycling exercise.

In the present study, intracortical communication between mid/anterior insular and motor cortex was investigated during a fatiguing cycling exercise. From 16 healthy male subjects performing a constant-load test at 60% peak oxygen consumption (VO(2peak)) until volitional exhaustion, electroencephalography data were analysed during repetitive, artefact-free periods of 1-min duration. To quantify fatigue-induced intracortical communication, mean intra-hemispheric lagged phase synchronization between mid/anterior insular and motor cortex was calculated: (i) at the beginning of cycling; (ii) at the end of cycling; and (iii) during recovery cycling. Results revealed significantly increased lagged phase synchronization at the end of cycling, which returned to baseline during recovery cycling after subjects' cessation of exercise. Following previous imaging studies reporting the mid/anterior insular cortex as an essential instance processing a variety of sensory stimuli and signalling forthcoming physiological threat, our results provide further evidence that during a fatiguing exercise this structure might not only integrate and evaluate sensory information from the periphery, but also act in communication with the motor cortex. To the best of our knowledge, this is the first study to empirically demonstrate that muscle fatigue leads to changes in interaction between structures of a brain's neural network.

Limitation of physical performance in a muscle fatiguing handgrip exercise is mediated by thalamo-insular activity.

In this study, we investigated central/supraspinal processes mediating cessation of a muscle fatiguing exercise. Fifteen male subjects performed 39 intermittent, isometric handgrip contractions (13 s on, 5-6 s off) with the dominant right hand while brain activation was assessed by means of functional magnetic resonance imaging (fMRI). An adaptive, partly stochastic protocol was designed such that in approximately 50% of the contraction trials the required force could not be held until the end of the trial (task failure trial). Trials performed in compliance with the force requirements (succeeded trial) were compared with task failure trials concerning neural activity during a small time window before task failure occurred. The data revealed significantly increased activation contralaterally in both the mid/anterior insular cortex and the thalamus during the investigated time window in the case of subsequent task failure. In accordance with other studies investigating sensations that alert the organism to urgent homeostatic imbalance such as air hunger, hunger for food, and pain, we assume that an increased thalamo-insular activation in the context of a fatigue-induced handgrip exercise could reflect increased homeostatic disturbance in the exercising muscle and may be of essential importance by mediating task failure to maintain the integrity of the organism.

Mitochondrial capacity is affected by glycemic status in young untrained women with type 1 diabetes but is not impaired relative to healthy untrained women.

In this study, we examined whether glycemic status influences aerobic function in women with type 1 diabetes and whether aerobic function is reduced relative to healthy women. To this end, we compared several factors determining aerobic function of 29 young sedentary asymptomatic women (CON) with 9 women of similar age and activity level with type 1 diabetes [DIA, HbA1c range = 6.9-8.2%]. Calf muscle mitochondrial capacity was estimated by (31)P-magnetic resonance spectroscopy. Capillarization and muscle fiber oxidative enzyme activity were assessed from vastus lateralis and soleus muscle biopsies. Oxygen uptake and cardiac output were evaluated by ergospirometry and N(2)O/SF(6) rebreathing. Calf muscle mitochondrial capacity was not different between CON and DIA, as indicated by the identical calculated maximal rates of oxidative ATP synthesis [0.0307 (0.0070) vs. 0.0309 (0.0058) s(-1), P = 0.930]. Notably, HbA1c was negatively correlated with mitochondrial capacity in DIA (R(2) = 0.475, P = 0.040). Although HbA1c was negatively correlated with cardiac output (R(2) = 0.742, P = 0.013) in DIA, there was no difference between CON and DIA in maximal oxygen consumption [2.17 (0.34) vs. 2.21 (0.32) l/min, P = 0.764], cardiac output [12.1 (1.9) vs. 12.3 (1.8) l/min, P = 0.783], and endurance capacity [532 (212) vs. 471 (119) s, P = 0.475]. There was also no difference between the two groups either in the oxidative enzyme activity or capillary-to-fiber ratio. We conclude that mitochondrial capacity depends on HbA1c in untrained women with type 1 diabetes but is not reduced relative to untrained healthy women.

Spinal opioid receptor-sensitive muscle afferents contribute to the fatigue-induced increase in intracortical inhibition in healthy humans.

We investigated the influence of spinal opioid receptor-sensitive muscle afferents on cortical changes following fatiguing unilateral knee-extensor exercise. On separate days, seven subjects performed an identical five sets of intermittent isometric right-quadriceps contractions, each consisting of eight submaximal contractions [63 ± 7% maximal voluntary contraction (MVC)] and one MVC. The exercise was performed following either lumbar interspinous saline injection or lumbar intrathecal fentanyl injection blocking the central projection of spinal opioid receptor-sensitive lower limb muscle afferents. To quantify exercise-induced peripheral fatigue, quadriceps twitch force (Q(tw,pot)) was assessed via supramaximal magnetic femoral nerve stimulation before and after exercise. Motor evoked potentials and cortical silent periods (CSPs) were evaluated via transcranial magnetic stimulation of the motor cortex during a 3% MVC pre-activation period immediately following exercise. End-exercise quadriceps fatigue was significant and similar in both conditions (Q(tw,pot) -35 and -39% for placebo and fentanyl, respectively; P = 0.38). Immediately following exercise on both days, motor evoked potentials were similar to those obtained prior to exercise. Compared with pre-exercise baseline, CSP in the placebo trial was 21 ± 5% longer postexercise (P < 0.01). In contrast, CSP following the fentanyl trial was not significantly prolonged compared with the pre-exercise baseline (6 ± 4%). Our findings suggest that the central effects of spinal opioid receptor-sensitive muscle afferents might facilitate the fatigue-induced increase in CSP. Furthermore, since the CSP is thought to reflect inhibitory intracortical interneuron activity, which may contribute to central fatigue, our findings imply that spinal opioid receptor-sensitive muscle afferents might influence central fatigue by facilitating intracortical inhibition.

Cardiac output but not stroke volume is similar in a Wingate and VO2peak test in young men.

Wingate test (WT) training programmes lasting 2-3 weeks lead to improved peak oxygen consumption. If a single 30 s WT was capable of significantly increasing stroke volume and cardiac output, the increase in peak oxygen consumption could possibly be explained by improved oxygen delivery. Thus, we investigated whether a single WT increases stroke volume and cardiac output to similar levels than those obtained at peak exercise during a graded cycling exercise test (GXT) to exhaustion. Fifteen healthy young men (peak oxygen consumption 45.0 ± 5.3 ml kg(-1) min(-1)) performed one WT and one GXT on separate days in randomised order. During the tests, we estimated cardiac output using inert gas rebreathing (nitrous oxide and sulphur hexafluoride) and subsequently calculated stroke volume. We found that cardiac output was similar (18.2 ± 3.3 vs. 17.9 ± 2.6 l min(-1); P = 0.744), stroke volume was higher (127 ± 37 vs. 94 ± 15 ml; P < 0.001), and heart rate was lower (149 ± 26 vs. 190 ± 12 beats min(-1); P < 0.001) at the end (27 ± 2 s) of a WT as compared to peak exercise during a GXT. Our results suggest that a single WT produces a haemodynamic response which is characterised by similar cardiac output, higher stroke volume and lower heart rate as compared to peak exercise during a GXT.

Lactate minimum is valid to estimate maximal lactate steady state in moderately and highly trained subjects.

Some evidence exists that the determination of maximal lactate steady state (MLSS) with lactate minimum (LM) in highly trained athletes is not as accurate as in less trained athletes. Therefore, we compared power output at LM with power output MLSS in moderately up to highly trained subjects. 63 subjects performed a test on a cycle ergometer to determine power output at LM and 3 or more constant-load tests of 30 minutes to determine power output at MLSS. Mean power output at LM (245 ± 29 W; mean ± SD) was slightly lower than power output at MLSS (255 ± 32 W). The correlation between power output at MLSS and LM was high, and the regression line runs parallel to the line of identity showing that the results of highly trained subjects agree with the results of less trained subjects (LM and MLSS r = 0.867, p < 0.001). The modified blood-lactate kinetic in highly trained athletes compared with less trained persons does not impair accuracy at LM. Therefore, we suggest LM as a valid and meaningful concept to estimate power output at MLSS in 1 single test in moderately up to highly trained athletes.

Impact of pulmonary system limitations on locomotor muscle fatigue in patients with COPD.

We examined the effects of respiratory muscle work [inspiratory (W(r-insp)); expiratory (W(r-exp))] and arterial oxygenation (Sp(O(2))) on exercise-induced locomotor muscle fatigue in patients with chronic obstructive pulmonary disease (COPD). Eight patients (FEV, 48 +/- 4%) performed constant-load cycling to exhaustion (Ctrl; 9.8 +/- 1.2 min). In subsequent trials, the identical exercise was repeated with 1) proportional assist ventilation + heliox (PAV); 2) heliox (He:21% O(2)); 3) 60% O(2) inspirate (hyperoxia); or 4) hyperoxic heliox mixture (He:40% O(2)). Five age-matched healthy control subjects performed Ctrl exercise at the same relative workload but for 14.7 min ( approximately best COPD performance). Exercise-induced quadriceps fatigue was assessed via changes in quadriceps twitch force (Q(tw,pot)) from before to 10 min after exercise in response to supramaximal femoral nerve stimulation. During Ctrl, absolute workload (124 +/- 6 vs. 62 +/- 7 W), W(r-insp) (207 +/- 18 vs. 301 +/- 37 cmH(2)O x s x min(-1)), W(r-exp) (172 +/- 15 vs. 635 +/- 58 cmH(2)O x s x min(-1)), and Sp(O(2)) (96 +/- 1% vs. 87 +/- 3%) differed between control subjects and patients. Various interventions altered W(r-insp), W(r-exp), and Sp(O(2)) from Ctrl (PAV: -55 +/- 5%, -21 +/- 7%, +6 +/- 2%; He:21% O(2): -16 +/- 2%, -25 +/- 5%, +4 +/- 1%; hyperoxia: -11 +/- 2%, -17 +/- 4%, +16 +/- 4%; He:40% O(2): -22 +/- 2%, -27 +/- 6%, +15 +/- 4%). Ten minutes after Ctrl exercise, Q(tw,pot) was reduced by 25 +/- 2% (P < 0.01) in all COPD and 2 +/- 1% (P = 0.07) in healthy control subjects. In COPD, DeltaQ(tw,pot) was attenuated by one-third after each interventional trial; however, most of the exercise-induced reductions in Q(tw,pot) remained. Our findings suggest that the high susceptibility to locomotor muscle fatigue in patients with COPD is in part attributable to insufficient O(2) transport as a consequence of exaggerated arterial hypoxemia and/or excessive respiratory muscle work but also support a critical role for the well-known altered intrinsic muscle characteristics in these patients.

Non-invasive haemodynamic assessments using Innocor during standard graded exercise tests.

Cardiac output (Q) and stroke volume (V(S)) represent primary determinants of cardiovascular performance and should therefore be determined for performance diagnostics purposes. Since it is unknown, whether measurements of Q and V(S) can be performed by means of Innocor during standard graded exercise tests (GXTs), and whether current GXT stages are sufficiently long for the measurements to take place, we determined Q and V(S) at an early and late point in time on submaximal 2 min GXT stages. 16 male cyclists (age 25.4 +/- 2.9 years, body mass 71.2 +/- 5.0 kg) performed three GXTs and we determined Q and V(S) after 46 and 103 s at 69, 77, and 85% peak power. We found that the rebreathings could easily be incorporated into the GXTs and that Q and V(S) remained unchanged between the two points in time on the same GXT stage (69% peak power, Q: 18.1 +/- 2.1 vs. 18.2 +/- 2.3 l min(-1), V(S): 126 +/- 18 vs. 123 +/- 21 ml; 77% peak power, Q: 20.7 +/- 2.6 vs. 21.0 +/- 2.3 l min(-1), V(S): 132 +/- 18 vs. 131 +/- 18 ml; 85% peak power, Q: 21.6 +/- 2.4 vs. 21.8 +/- 2.7 l min(-1), V(S): 131 +/- 17 vs. 131 +/- 22 ml). We conclude that Innocor may be a useful device for assessing Q and V(S) during GXTs, and that the adaptation of Q and V(S) to exercise-to-exercise transitions at moderate to high submaximal power outputs is fast enough for 1 and 2 min GXT stage durations.

The energetically optimal cadence decreases after prolonged cycling exercise.

This study investigated the change in the energetically optimal cadence after prolonged cycling. The energetically optimal cadence (EOC) was determined in 14 experienced cyclists by pulmonary gas exchange at six different cadences (100-50 rpm at 10 rpm intervals). The determination of the EOC was repeated after a prolonged cycling exercise of 55 min duration, where cadence was fixed either at high (>95 rpm) or low (<55 rpm) pedalling rates. The EOC decreased after prolonged cycling exercise at a high as well as at a low fixed cadence (P < 0.01). According to the generalized muscle equations of Hill, this indicates that most likely more type I muscle fibres contribute to muscular power output after fatiguing cycling exercise compared to cycling in the beginning of an exercise bout. We suggest that the determination of EOC might be a potential non-invasive method to detect the qualitative changes in activated muscle fibres, which needs further investigation.

Time to exhaustion at maximal lactate steady state is similar for cycling and running in moderately trained subjects.

We compared time to exhaustion (t(lim)) at maximal lactate steady state (MLSS) between cycling and running, investigated if oxygen consumption, ventilation, blood lactate concentration, and perceived exertion differ between the exercise modes, and established whether MLSS can be determined for cycling and running using the same criteria. MLSS was determined in 15 moderately trained men (30 +/- 6 years, 77 +/- 6 kg) by several constant-load tests to exhaustion in cycling and running. Heart rate, oxygen consumption, and ventilation were recorded continuously. Blood lactate concentration and perceived exertion were measured every 5 min. t (lim) (37.7 +/- 8.9 vs. 34.4 +/- 5.4 min) and perceived exertion (7.2 +/- 1.7 vs. 7.2 +/- 1.5) were similar for cycling and running. Heart rate (165 +/- 8 vs. 175 +/- 10 min(-1); P < 0.01), oxygen consumption (3.1 +/- 0.3 vs. 3.4 +/- 0.3 l min(-1); P < 0.001) and ventilation (93 +/- 12 vs. 103 +/- 16 l min(-1); P < 0.01) were lower for cycling compared to running, respectively, whereas blood lactate concentration (5.6 +/- 1.7 vs. 4.3 +/- 1.3 mmol l(-1); P < 0.05) was higher for cycling. t(lim) at MLSS is similar for cycling and running, despite absolute differences in heart rate, ventilation, blood lactate concentration, and oxygen consumption. This may be explained by the relatively equal cardiorespiratory demand at MLSS. Additionally, the similar t(lim) for cycling and running allows the same criteria to be used for determining MLSS in both exercise modes.

Effect of respiratory muscle endurance training on respiratory sensations, respiratory control and exercise performance: a 15-year experience.

Respiratory muscle endurance training (RMET) can improve respiratory muscle endurance as well as cycling and swimming endurance. Whether these improvements are caused by reduced perception of adverse respiratory sensations and/or a change in ventilatory output remains unclear. We re-analysed nine (five randomized controlled) RMET studies performed in our laboratory. One hundred and thirty-five healthy subjects completed either RMET [i.e. an average of 12.4+/-4.9h (median 10; range 10-25) of normocapnic hyperpnoea at 60-85% of maximal voluntary ventilation achieved during 27+/-11 sessions (median 20; range 20-50) of 29+/-4min (median 30; range 15-30) duration over 6.5+/-4.2 weeks (median 4; range 4-15), n=90] or no RMET (CON, n=45). Before and after RMET/CON, respiratory ( approximately 70% MVV) and cycling (70-85% maximal power) endurance were tested. RMET increased both respiratory and cycling endurance, reduced perception of breathlessness and respiratory exertion during volitional and exercise-induced hyperpnoea, and slightly increased ventilation at identical workloads. Decreased respiratory sensations did not correlate with improved cycling endurance. Changes in ventilation correlated with changes in cycling endurance in both groups. We conclude that reduced adverse respiratory sensations after RMET are unlikely to cause the improvements in cycling endurance, that the level of ventilation seems to affect cycling endurance and that additional factors must contribute to the improvements in cycling endurance after RMET.

The influence of a mouthpiece and noseclip on breathing pattern at rest is reduced at high altitude.

The effects of the instrumentation by a mouthpiece (MP) and a noseclip (NC) on the ventilatory response to short time hypobaric hypoxia were studied in 10 healthy volunteers at rest. The subjects were exposed to simulated altitude of 500 m, 3000 m, 4000 m and again 500 m, each altitude being applied for 30 min in a hypobaric chamber. Resting minute ventilation (VE), tidal volume (VT) and respiratory frequency (fR) using inductive plethysmography were continuously measured in all subjects in a standardized half lying position. The recordings were carried out at each altitude during the first 10 min without MP and NC, then 10 min with them, and the last 10 min again without them. At 500 m during MP+NC breathing VE and VT were increased, whereas fR was not significantly changed. At 3000 m, the VE increase with MP+NC was no more significant and fR was decreased. These effects of MP+NC on respiration disappeared at 4000 m and reappeared after the descent to 500 m. Furthermore, with and without MP and NC the variability of VE at 4000 m was significantly higher than at 500 m before ascent, and in all altitudes the variability of VT was significantly reduced by the MP+NC. It is concluded that the influence of MP+NC on VE, VT and fR is reduced or even abolished at high altitude, whereas the hypoxia induced increase of VE variability is not affected by the instrumentation.

Respiratory muscle training improves respiratory muscle endurance but not exercise tolerance in children with cystic fibrosis.

BACKGROUND: Respiratory muscle endurance (RME) training has been shown to increase exercise endurance and lung function in adults with cystic fibrosis (CF). We conducted an interventional study to investigate the effectiveness of RME training on CF-related health outcomes in children. METHODS: In a crossover trial, 22 children, aged 9-18 years, with CF performed 8 weeks of RME training and standard chest physiotherapy in a randomized sequence separated by a 1 week washout period. All children underwent training sessions using the RME training device before beginning the study. The primary outcomes were RME (in minutes) and exercise endurance (in minutes). Data were analyzed according to the intention-to-treat principle. RESULTS: Sixteen of 22 children (73%) completed the study. Study dropouts tended to be older with more advanced lung disease. After RME training, respiratory muscle endurance significantly increased by 7.03 ± 8.15 min (mean ± standard deviation, P < 0.001), whereas exercise endurance was unchanged by RME training (0.80 ± 2.58 min, P = 0.169). No significant improvement in secondary outcomes (lung function, CF quality of life, and CF clinical score) were observed. The small sample size and short intervention time have to be acknowledged as limitations of our study. CONCLUSIONS: RME training led to a significant increase in respiratory muscle endurance in children with CF. However, RME training did not improve exercise endurance or other CF-related health outcomes. Thus, our results do not support the routine use of RME training in the care of children with CF. Future studies in larger populations and with prolonged intervention time may overcome the limitations of our study. Pediatr Pulmonol. 2017;52:331-336. © 2017 Wiley Periodicals, Inc.

Risk Factors for Knee Injury in Golf: A Systematic Review.

BACKGROUND: Golf is commonly considered a low-impact sport that carries little risk of injury to the knee and is generally allowed following total knee arthroplasty (TKA). Kinematic and kinetic studies of the golf swing have reported results relevant to the knee, but consensus as to the loads experienced during a swing and how the biomechanics of an individual's technique may expose the knee to risk of injury is lacking. OBJECTIVES: Our objective was to establish (1) the prevalence of knee injury resulting from participation in golf and (2) the risk factors for knee injury from a biomechanical perspective, based on an improved understanding of the internal loading conditions and kinematics that occur in the knee from the time of addressing the ball to the end of the follow-through. METHODS: A systematic literature search was conducted to determine the injury rate, kinematic patterns, loading, and muscle activity of the knee during golf. RESULTS: A knee injury prevalence of 3-18% was established among both professional and amateur players, with no clear dependence on skill level or sex; however, older players appear at greater risk of injury. Studies reporting kinematics indicate that the lead knee is exposed to a complex series of motions involving rapid extension and large magnitudes of tibial internal rotation, conditions that may pose risks to the structures of a natural knee or TKA. To date, the loads experienced by the lead knee during a golf swing have been reported inconsistently in the literature. Compressive loads ranging from 100 to 440% bodyweight have been calculated and measured using methods including inverse dynamics analysis and instrumented knee implants. Additionally, the magnitude of loading appears to be independent of the club used. CONCLUSIONS: This review is the first to highlight the lack of consensus regarding knee loading during the golf swing and the associated risks of injury. Results from the literature suggest the lead knee is subject to a higher magnitude of stress and more demanding motions than the trail knee. Therefore, recommendations regarding return to golf following knee injury or surgical intervention should carefully consider the laterality of the injury.

Effect of Regular Yoga Practice on Respiratory Regulation and Exercise Performance.

Yoga alters spontaneous respiratory regulation and reduces hypoxic and hypercapnic ventilatory responses. Since a lower ventilatory response is associated with an improved endurance capacity during whole-body exercise, we tested whether yogic subjects (YOGA) show an increased endurance capacity compared to matched non-yogic individuals (CON) with similar physical activity levels. Resting ventilation, the ventilatory response to hypercapnia, passive leg movement and exercise, as well as endurance performance were assessed. YOGA (n = 9), compared to CONTROL (n = 6), had a higher tidal volume at rest (0.7±0.2 vs. 0.5±0.1 l, p = 0.034) and a reduced ventilatory response to hypercapnia (33±15 vs. 47±15 l·min(-1), p = 0.048). A YOGA subgroup (n = 6) with maximal performance similar to CONTROL showed a blunted ventilatory response to passive cycling (11±2 vs. 14±2 l·min(-1), p = 0.039) and a tendency towards lower exercise ventilation (33±2 vs. 36±3 l·min(-1), p = 0.094) while cycling endurance (YOGA: 17.3±3.3; CON: 19.6±8.5 min, p = 0.276) did not differ. Thus, yoga practice was not associated with improved exercise capacity nor with significant changes in exercise ventilation despite a significantly different respiratory regulation at rest and in response to hypercapnia and passive leg movement.