Cytokine responses to exercise and activity in patients with chronic fatigue syndrome: case-control study.

Chronic fatigue syndrome (CFS) is characterized by fatigue after exertion. A systematic review suggested that transforming growth factor (TGF)-ß concentrations are often elevated in cases of CFS when compared to healthy controls. This study attempted to replicate this finding and investigate whether post-exertional symptoms were associated with altered cytokine protein concentrations and their RNA in CFS patients. Twenty-four patients fulfilling Centers for Disease Control criteria for CFS, but with no comorbid psychiatric disorders, were recruited from two CFS clinics in London, UK. Twenty-one healthy, sedentary controls were matched by gender, age and other variables. Circulating proteins and RNA were measured for TGF-ß, tumour necrosis factor (TNF), interleukin (IL)-8, IL-6 and IL-1ß. We measured six further cytokine protein concentrations (IL-2, IL-4, IL-5, IL-10, IL-12p70, and interferon (IFN)-γ). Measures were taken at rest, and before and after both commuting and aerobic exercise. CFS cases had higher TGF-ß protein levels compared to controls at rest (median (quartiles) = 43·9 (19·2, 61·8) versus 18·9 (16·1, 30·0) ng/ml) (P = 0·003), and consistently so over a 9-day period. However, this was a spurious finding due to variation between different assay batches. There were no differences between groups in changes to TGF-ß protein concentrations after either commuting or exercise. All other cytokine protein and RNA levels were similar between cases and controls. Post-exertional symptoms and perceived effort were not associated with any increased cytokines. We were unable to replicate previously found elevations in circulating cytokine concentrations, suggesting that elevated circulating cytokines are not important in the pathophysiology of CFS.

Beef palatability and its relationship with protein degradation and muscle fibre type profile in longissimus thoracis in Alentejana breed from divergent growth pathways.

The traditional beef production in the South of Portugal is based on a discontinuous growth (DG) system that requires lower external inputs and could enhance meat quality and financial returns to cattle producers. This system allows farmers to take advantage of the bull's compensatory growth when the pasture is abundant and finishes the cattle on concentrates for 2 to 3 months before slaughter. The fast gain rate before slaughter could be a valuable strategy to improve tenderness and to reduce its inconsistency in beef production. Therefore, the aim of this study was to evaluate the effects of production system (continuous growth (CG) v. DG) on longissimus thoracis muscle properties from Alentejana bulls. In total, 40 Alentejana male calves were allocated to two distinct feeding regimes: in the CG system, animals were fed concentrate plus hay and slaughtered at 18 months of age, whereas in the DG system, animals were fed on hay until 15 months of age and then fed the same diet provided to the CG group until 24 months of age. The DG system had a positive impact on meat tenderness (P<0.001) and global acceptability (P<0.001). DG bulls had greater fibre cross-sectional area (CSA) of glycolytic fibres (P<0.05) and relative area of the muscle (RA) occupied by type IIX fibres (P<0.01) and greater levels of α-actinin (P<0.05) and myosin light chain 2 (P<0.01) proteins, and pH24h (P<0.01) than CG bulls. The latter had greater CSA of type I (P<0.05) and type IIA (P<0.01) and greater RA of type IIA (P<0.05) and oxidative (P<0.05) than CG bulls. The compensatory growth production system had a positive impact on meat tenderness and global acceptability, overcoming the negative effects of slaughter of the bulls at a later age. The DG beef system could be a worthwhile strategy of beef production in Mediterranean areas due to the low-quality pasture in summer.

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.

Lactate threshold does not influence metabolic responses during exercise in cyclists.

The purpose of this study was to compare plasma markers of metabolic stress and other physiological parameters during prolonged endurance exercise of different intensity in trained subjects possessing a "high" or "low" lactate threshold (LT) expressed as a percentage (%) of peak power output (PPO). Fifteen trained male cyclists completed an incremental exercise test for determination of PPO and the LT (% PPO). Each subject then completed a 90-min and 20-min exercise trial at an intensity representing 75 and 85 % of PPO, respectively. Blood lactate (La), as well as plasma hypoxanthine (Hx) and uric acid (UA) were measured during each exercise trial. The responses in two groups, one (n = 8) with a LT approximately 65 % PPO (LT (low)), the other group (n = 7) with a LT approximately 75 % (LT (high)) (p < 0.01), were then compared. With the exception of UA, La and Hx increased significantly (p < 0.01) throughout each exercise trial compared to rest. However, there were no significant differences in each trial between the two groups of cyclists. There were also no significant differences in the other physiological parameters in each exercise trial between the subjects in LT (low) and LT (high). This study demonstrates that in trained cyclists homogeneous in terms of PPO, plasma markers of metabolic demand during prolonged exercise are not influenced by the LT when measured in an incremental exercise test.

The consequences of swim, cycle, and run performance on overall result in elite olympic distance triathlon.

This study examined the consequences of performance in swim, cycle, and run phases on overall race finish in an elite "draft legal" Olympic distance (OD) triathlon. The subjects were 24 male athletes grouped by rank order into the top 50 % (n = 12) and bottom 50 % (n = 12) of the race population. Swimming velocity (m x s (-1)), cycling speed (km x h (-1)), and running velocity (m x s (-1)) were measured at regular intervals using a global positioning system, chip timing system, and video analysis. Actual rank after each stage and overall was obtained from the race results and video analysis. The top 50 % athletes overall swam faster over the first 400 m of the swim phase (p > 0.05). Their swim ranking was lower (p < 0.01) than the bottom 50 % athletes after this stage. There were no significant differences in actual race position between the groups after the cycle. However, the bottom 50 % athletes after the swim stage cycled faster (p < 0.01) at 13.4 km of the cycle. Speed at 13.4 km of the cycle stage was inversely correlated (r = 0.60, p < 0.01) to running performance. Performance (rank and velocity) in the running stage was highly correlated with overall race result (r = 0.86 and - 0.53, respectively, both p > 0.01). It appears that inferior swimming performance can result in a tactic that involves greater work in the initial stages of the cycle stage of elite OD racing, and may influence subsequent running performance.

Peak power output, the lactate threshold, and time trial performance in cyclists.

PURPOSE: To determine the relationship between maximum workload (W(peak)), the workload at the onset of blood lactate accumulation (W(OBLA)), the lactate threshold (W(LTlog)) and the D(max) lactate threshold, and the average power output obtained during a 90-min (W(90-min)) and a 20-min (W(20-min)) time trial (TT) in a group of well-trained cyclists. METHODS: Nine male cyclists (.VO(2max) 62.7 +/- 0.8 mL.kg(-1).min(-1)) who were competing regularly in triathlon or cycle TT were recruited for the study. Each cyclist performed four tests on an SRM isokinetic cycle ergometer over a 2-wk period. The tests comprised 1) a continuous incremental ramp test for determination of maximal oxygen uptake (.VO(2max) (L.min(-1) and mL.kg(-1).min(-1)); 2) a continuous incremental lactate test to measure W(peak), W(OBLA), W(LTlog), and the D(max) lactate threshold; and 3) a 20-min TT and 4) a 90-min TT, both to determine the average power output (in watts). RESULTS: The average power output during the 90-min TT (W(90-min)) was significantly (P < 0.01) correlated with W(peak) (r = 0.91), W(LTlog) (r = 0.91), and the D(max) lactate threshold (r = 0.77, P < 0.05). In contrast, W(20-min) was significantly (P < 0.05) related to .VO(2max) (L.min(-1)) (r = 0.69) and W(LTlog) (r = 0.67). The D(max) lactate threshold was not significantly correlated to W(20-min) (r = 0.45). Furthermore, W(OBLA) was not correlated to W(90-min) (r = 0.54) or W(20-min) (r = 0.23). In addition, .VO(2max) (mL.kg(-1).min(-1)) was not significantly related to W(90-min) (r = 0.11) or W(20-min) (r = 0.47). CONCLUSION: The results of this study demonstrate that in subelite cyclists the relationship between maximum power output and the power output at the lactate threshold, obtained during an incremental exercise test, may change depending on the length of the TT that is completed.

Physiological and biomechanical adaptations to the cycle to run transition in Olympic triathlon: review and practical recommendations for training.

Current knowledge of the physiological, biomechanical, and sensory effects of the cycle to run transition in the Olympic triathlon (1.5 km, 10 km, 40 km) is reviewed and implications for the training of junior and elite triathletes are discussed. Triathlon running elicits hyperventilation, increased heart rate, decreased pulmonary compliance, and exercise induced hypoxaemia. This may be due to exercise intensity, ventilatory muscle fatigue, dehydration, muscle fibre damage, a shift in metabolism towards fat oxidation, and depleted glycogen stores after a 40 km cycle. The energy cost (CR) of running during the cycle to run transition is also increased over that of control running. The increase in CR varies from 1.6% to 11.6% and is a reflection of triathlete ability level. This increase may be partly related to kinematic alterations, but research suggests that most biomechanical parameters are unchanged. A more forward leaning trunk inclination is the most significant observation reported. Running pattern, and thus running economy, could also be influenced by sensorimotor perturbations related to the change in posture. Technical skill in the transition area is obviously very important. The conditions under which the preceding cycling section is performed-that is, steady state or stochastic power output, drafting or non-drafting-are likely to influence the speed of adjustment to transition. The extent to which a decrease in the average 10 km running speed occurs during competition must be investigated further. It is clear that the higher the athlete is placed in the field at the end of the bike section, the greater the importance to their finishing position of both a quick transition area time and optimal adjustment to the physiological demands of the cycle to run transition. The need for, and current methods of, training to prepare junior and elite triathletes for a better transition are critically reviewed in light of the effects of sequential cycle to run exercise.

Injury and training characteristics of male Elite, Development Squad, and Club triathletes.

Links between overuse injury prevalence in triathletes training for 1.5km, 40km, 10km triathlon and both intrinsic and extrinsic factors were assessed in 12 Elite, 17 Development and 87 male Club triathletes by a five year retrospective questionnaire. Elite, Development and Club triathletes differed in training mileage, duration and number of workouts but not in overall injury prevalence, distribution, and severity. Overuse injury occurred in 75.0% of male Elite Squad, 75.0% of Development Squad and 56.3% of Club athletes with 1.9-2.9 sites affected. The most common injuries - the achilles tendon (10.3-17.9%), lower back (15.8-17.9%) and knee (14.2-21.9% of injuries) - were also among the most severe. Running injuries accounted for more of the total number of injuries than cycling injuries in Elite (62.1 % vs 34.5%, p<0.05), Development (64.3% vs 25.0%, p<0.05) and Club triathletes (58.7% vs 15.9%, p<0.05). The number of running injuries sustained correlated with triathlon training distance, cycling distance (p<0.03), swimming distance (p<0.01), number of triathlon workouts (p<0.03) and number of running sessions (p<0.03) within one weeks race training. The number of overuse injuries sustained during cycling correlated with time spent running and cycling.