Henri Nielens

Beneficial metabolic adaptations due to endurance exercise training in the fasted state

Training with limited carbohydrate availability can stimulate adaptations in muscle cells to facilitate energy production via fat oxidation. Here we investigated the effect of consistent training in the fasted state, vs. training in the fed state, on muscle metabolism and substrate selection during fasted exercise. Twenty young male volunteers participated in a 6-wk endurance training program (1-1.5 h cycling at ∼70% Vo(₂max), 4 days/wk) while receiving isocaloric carbohydrate-rich diets. Half of the subjects trained in the fasted state (F; n = 10), while the others ingested ample carbohydrates before (∼160 g) and during (1 g·kg body wt⁻¹·h⁻¹) the training sessions (CHO; n = 10). The training similarly increased Vo(₂max) (+9%) and performance in a 60-min simulated time trial (+8%) in both groups (P < 0.01). Metabolic measurements were made during a 2-h constant-load exercise bout in the fasted state at ∼65% pretraining Vo(₂max). In F, exercise-induced intramyocellular lipid (IMCL) breakdown was enhanced in type I fibers (P < 0.05) and tended to be increased in type IIa fibers (P = 0.07). Training did not affect IMCL breakdown in CHO. In addition, F (+21%) increased the exercise intensity corresponding to the maximal rate of fat oxidation more than did CHO (+6%) (P < 0.05). Furthermore, maximal citrate synthase (+47%) and β-hydroxyacyl coenzyme A dehydrogenase (+34%) activity was significantly upregulated in F (P < 0.05) but not in CHO. Also, only F prevented the development exercise-induced drop in blood glucose concentration (P < 0.05). In conclusion, F is more effective than CHO to increase muscular oxidative capacity and at the same time enhances exercise-induced net IMCL degradation. In addition, F but not CHO prevented drop of blood glucose concentration during fasting exercise.

Fitness and perceived exertion in patients with fibromyalgia syndrome

OBJECTIVE The aim of this study was to evaluate the cardiorespiratory fitness and perceived exertion of female patients with fibromyalgia syndrome (FMS) compared with that of healthy female subjects. DESIGN AND SUBJECTS This was designed as a cross-sectional case-control study, with a consecutive sample of 30 female patients with FMS and an age-matched control group of 67 healthy female subjects. SETTING This study was conducted at the multidisciplinary pain center of a university hospital in a city of more than 1 million inhabitants. OUTCOME MEASURES A cardiorespiratory fitness index (PWC65%/kg) and an original perceived exertion index (B65%) were obtained from the heart rates and perceived exertions scored on a 10-point Borg scale during a submaximal cycle ergometer test. Average indexes for the FMS patients and control subjects were compared. RESULTS The mean cardiorespiratory fitness index of the FMS patients was not significantly different from that of the controls. The mean perceived exertion index in the FMS patients was significantly greater than that of the controls, meaning that the FMS patients systematically reported higher ratings of perceived exertion during exercise. CONCLUSIONS Cardiorespiratory fitness, as expressed by a submaximal work capacity index, seems normal in female patients with FMS compared with age- and sex-matched healthy individuals. The fact that FMS patients overscore their perception of exertion may be due to a greater overlap of peripheral pain and perceived exertion perceptions during exercise. This observation should be noted when using perceived exertion scores to prescribe and monitor exercise in FMS patients.

Protective role of {alpha}-actinin-3 in the response to an acute eccentric exercise bout

The ACTN3 gene encodes for the alpha-actinin-3 protein, which has an important structural function in the Z line of the sarcomere in fast muscle fibers. A premature stop codon (R577X) polymorphism in the ACTN3 gene causes a complete loss of the protein in XX homozygotes. This study investigates a possible role for the alpha-actinin-3 protein in protecting the fast fiber from eccentric damage and studies repair mechanisms after a single eccentric exercise bout. Nineteen healthy young men (10 XX, 9 RR) performed 4 series of 20 maximal eccentric knee extensions with both legs. Blood (creatine kinase; CK) and muscle biopsy samples were taken to study differential expression of several anabolic (MyoD1, myogenin, MRF4, Myf5, IGF-1), catabolic (myostatin, MAFbx, and MURF-1), and contraction-induced muscle damage marker genes [cysteine- and glycine-rich protein 3 (CSRP3), CARP, HSP70, and IL-6] as well as a calcineurin signaling pathway marker (RCAN1). Baseline mRNA content of CSRP3 and MyoD1 was 49 + or - 12 and 67 + or - 25% higher in the XX compared with the RR group (P = 0.01-0.045). However, satellite cell number was not different between XX and RR individuals. After eccentric exercise, XX individuals tended to have higher serum CK activity (P = 0.10) and had higher pain scores than RR individuals. However, CSRP3 (P = 0.058) and MyoD1 (P = 0.08) mRNA expression tended to be higher after training in RR individuals compared with XX alpha-actinin-3-deficient subjects. This study suggests a protective role of alpha-actinin-3 protein in muscle damage after eccentric training and an improved stress-sensor signaling, although effects are small.

Cardiorespiratory fitness, physical activity level, and chronic pain : are men more affected than women?

ObjectiveTo evaluate the cardiorespiratory endurance (CRE) and physical activity level of patients with chronic pain compared with healthy subjects. Design and SubjectsCross-sectional study, with a consecutive sample of 55 patients with chronic pain (20 men, 35 women). Comparison of CRE and physical activity indices obtained in patients with data available in the literature for age-matched healthy subjects. SettingA multidisciplinary pain center in a city of more than 1,000,000 inhabitants. Outcome MeasuresA physical working capacity index (PWC65%/kg) and physical activity level scores and subscores obtained with two questionnaires (the Baecke and the Five-City Project questionnaires). ResultsThe physiological gender difference in CRE indices that characterizes healthy subjects was not observed in patients with chronic pain. When compared with values previously obtained in controls, male patients presented with a very significant 34% reduction in PWC65%/kg. The 17% reduction found in women hardly reached significance level. The Baecke total physical activity score was significantly higher in female than in male patients, a finding not observed in healthy controls. There was no significant difference between male and female patients in the Five-City Project total physical activity score expressed in kilocalories per day per kilogram (i.e., normalized for body weight), although data from the literature show that healthy men present with a significantly higher level of physical activity compared with healthy women. ConclusionsData on CRE and the physical activity level of patients with chronic pain obtained in this study show that chronic pain may have a greater impact on male than female patients. Sociocultural factors are probably at the origin of this phenomenon.

Perception of pain and exertion during exercise on a cycle ergometer in chronic pain patients

Hypothesis:Chronic pain patients (CPP) are generally thought to present with reduced fitness in relation with pain enhancement during exercise. A distortion of exertion perception may coexist, which could lead CPP to reduce physical activities. Design:Case-control study, with a nonrandomized consecutive sample that was age matched. Setting:A Chronic Pain Unit in a Multidisciplinary Pain Center of a university hospital in a city of > 1,000,000 inhabitants. Subjects:42 CPP referred for evaluation and 34 controls (staff members and relatives). Outcome measures:Fitness index and exertion perception index was obtained by a cycle ergometer test. Trend analysis was performed on pain scores reported on a visual analogue scale during exertion. Results:Male CPP mean fitness index was found to be significantly reduced. No difference in exertion perception was found between groups. Trend analysis of reported pain revealed that 49% of CPP showed a positive trend, 5% a negative trend, and 46% showed no significant trend as exercise intensity increased. There was no significant relation between type of trend and fitness nor exertion perception index. Conclusions:Only male CPP have a reduced work capacity. Exertion perception seems normal among CPP. The possible distortion of exertion perception as a causal factor in the reduced fitness of CPP has to be rejected. Lack of significant correlation between type of trend of pain while exercising on a cycle ergometer and fitness index shows that one should be careful in proposing that reduced fitness is only related to pain enhancement during exercise in CPP.

High-fat diet overrules the effects of training on fiber-specific intramyocellular lipid utilization during exercise

In this study, we compared the effects of endurance training in the fasted state (F) vs. the fed state [ample carbohydrate intake (CHO)] on exercise-induced intramyocellular lipid (IMCL) and glycogen utilization during a 6-wk period of a hypercaloric (∼+30% kcal/day) fat-rich diet (HFD; 50% of kcal). Healthy male volunteers (18-25 yrs) received a HFD in conjunction with endurance training (four times, 60-90 min/wk) either in F (n = 10) or with CHO before and during exercise sessions (n = 10). The control group (n = 7) received a HFD without training and increased body weight by ∼3 kg (P < 0.001). Before and after a HFD, the subjects performed a 2-h constant-load bicycle exercise test in F at ∼70% maximal oxygen uptake rate. A HFD, both in the absence (F) or presence (CHO) of training, elevated basal IMCL content by ∼50% in type I and by ∼75% in type IIa fibers (P < 0.05). Independent of training in F or CHO, a HFD, as such, stimulated exercise-induced net IMCL breakdown by approximately twofold in type I and by approximately fourfold in type IIa fibers. Furthermore, exercise-induced net muscle glycogen breakdown was not significantly affected by a HFD. It is concluded that a HFD stimulates net IMCL degradation by increasing basal IMCL content during exercise in type I and especially IIa fibers. Furthermore, a hypercaloric HFD provides adequate amounts of carbohydrates to maintain high muscle glycogen content during training and does not impair exercise-induced muscle glycogen breakdown.

Use of kinematic algorithms to distinguish people with chronic non-specific low back pain from asymptomatic subjects: a validation study.

OBJECTIVE To determine whether kinematic algorithms can distinguish subjects with chronic non-specific low back pain from asymptomatic subjects and subjects simulating low back pain, during trunk motion tasks. DESIGN Comparative cohort study. SUBJECTS A total of 90 subjects composed 3 groups; 45 chronic non-specific low back pain patients in the CLBP group; 45 asymptomatic controls people in the asymptomatic controls group. 20/45 subjects from the asymptomatic controls group composed the CLBP simulators group as well. METHOD During performance of 7 standardized trunk motion tasks 6 spinal segments from the kinematic spine model were recorded by 8 infrared cameras. Two logit scores, for range of motion and speed, were used to investigate differences between the groups. Group allocation based on logit scores was also calculated, allowing the assessment of sensitivity and specificity of the algorithms. RESULTS For the 90 subjects (pooled data), the logit scores for range of motion and speed demonstrated highly significant differences between groups (p < 0.001). The logit score means and standard deviation (SD) values in the asymptomatic group (n = 45) and chronic non-specific low back pain group (n = 45), respectively, were -1.6 (SD 2.6) and 2.8 (SD 2.8) for range of motion and -2.6 (SD 2.5) and 1.2 (SD 1.9) for speed. The sensitivity and specificity (n = 90) for logit score for range of motion were 0.80/0.82 and for logit score for speed were 0.80/0.87, respectively. CONCLUSION These results support the validity of using 2 movement algorithms, range of motion and speed, to discriminate asymptomatic subjects from those with low back pain. However, people simulating low back pain cannot be distinguished from those with real low back pain using this method.