Sedentary behaviour and clustered metabolic risk in adolescents: the HELENA study

BACKGROUND AND AIMS

Although sedentary behaviours are linked with mortality for cardiovascular reasons, it is not clear whether they are negatively related with cardio-metabolic risk factors. The aim was to examine the association between time engaged in television (TV) viewing or playing with videogames and a clustered cardio-metabolic risk in adolescents.

METHODS AND RESULTS

Sedentary behaviours and physical activity were assessed in 769 adolescents (376 boys, aged 12.5-17.5 years) from the HELENA-CSS study. We measured systolic blood pressure, HOMA index, triglycerides, TC/HDL-c, VO₂max and the sum of four skinfolds, and a clustered metabolic risk index was computed. A multilevel regression model (by Poisson) was performed to calculate the prevalence ratio of having a clustered metabolic risk. In boys, playing >4 h/day with videogames (weekend) and moderate to vigorous PA (MVPA) was associated with cardio-metabolic risk after adjustment for age, maternal education and MVPA. In contrast, TV viewing was not associated with the presence of cardio-metabolic risk.

CONCLUSION

In boys, playing with videogames may impair cardio-metabolic health during the adolescence. Adolescents should be encouraged to increase their participation in physical activity of at least moderate intensity to obtain a more favourable risk factor profile.

The relationship between rating of perceived exertion and muscle activity during exhaustive constant-load cycling

The aims of this study were to verify the relationship between rating of perceived exertion (RPE) and electromyography (EMG) increases during exhaustive constant-load cycling bouts and, to compare and to correlate the power outputs corresponding to perceived exertion threshold (PET) and neuromuscular fatigue threshold (NFT). 11 men completed 3-4 different exhaustive constant-load cycling bouts on a cycle ergometer, being RPE and EMG measured throughout the bouts. The linear regression of the RPEslope and EMGslope against the power output identified the PET and NFT intensity, respectively. There was a significant relationship between RPEslope and EMGslope (R(2)=0.69; P<0.01). However, the linearity of RPEslope (R(2)=0.93±0.07) was significantly higher (P<0.001) than EMGslope (R(2)=0.63±0.25). In addition, the RPEslope and EMGslope were related to time to exhaustion (r=-0.59 and r=-0.60; P<0.001). There was no significant difference (P=0.42) between PET (201.5±27.9W) and NFT (210.3±22.6W) and they were significantly correlated (r=0.78; P=0.005). Therefore, the RPE and EMG increases during exhaustive constant-load cycling bouts are related and, PET and NFT intensities are similar and closely associated.

Electromyography response of the iliocostalis lumborum muscle during flexion, extension and rotation movements of the trunk in orthostatic and seated position

The action of the column extensor muscles has been studied through in the electromyography in various corporal postures. We verified the electromyography responses of the iliocostalis lumborum muscle during various movements and positions. 12 individuals males, sedentary, between 36 and 52 years old (average 46.16), weighing an average of 79.66 kilos, and with an average height of 173.0 cm, all working as drivers were studied. Electromyography with six channels and surface electrodes was used. The electrodes were placed on the right side of the trunk in the direction of the third and fifth lumbar vertebrae ICL2 and ICL1 respectively). In orthostatic position, the flexion movement presented RMS 31.18 (+/- 5.73) in ICL1 and 58.10 (+/- 14.81) in ICL2; in extension the RMS 32.46 (+/- 9.17) in ICL1 and 55.31 (+/- 16.70) in ICL2; in homolateral rotation the RMS 30.05 (+/- 10.60) in ICL1 and 53.29 (+/- 19.70) in ICL2; in heterolateral rotation the RMS 24.76 (+/- 5.99) in ICL1 and 44.79 (+/- 15.26) in ICL2. In seated in a chair without a back, the flexion presented RMS 22.42 (+/- 2.89) in ICL1 and 43.39 (+/- 5.68) in ICL2; in extension the RMS 22.47 (+/- 1.95) in ICL1 and 41.28 (+/- 6.20) in ICL2; in homolateral rotation the RMS 24.10 (+/- 3.97) in ICL1 and 47.94 (+/- 5.80) in ICL2; in heterolateral rotation, the RMS 22.59 (+/- 1.95) in ICL1 and 43.15 (+/- 5.71) in ICL2. In the position seated on the ground, the flexion presented RMS 22.83 (+/- 3.00) in ICL1 and 50.99 (+/- 11.19) in ICL2; in extension the RMS 22.39 (+/- 3.22) in ICL1 and 46.44 (+/- 8.19) in ICL2. The results are expressed in RMS, indicating the participation of the iliocostalis lumborum muscle during the movements undertaken. The place identified as ICL2 presented action potential of greater amplitude than the place identified as ICL1 in all movements and positions.

[Activation of the cardiac angiotensin-converting enzyme after myocardial infarction and its role in ventricular remodeling]

PURPOSE

To determine angiotensin converting enzyme (ACE) activity in the heart of infarcted rats and to investigate the effects of captopril and losartan on the post-infarction remodeling process.

METHODS

Myocardial infarction (MI) was produced in Wistar rats by ligature of the left coronary artery. Control rats (Con) underwent a sham surgery. MI and Con rats remained untreated or were treated with captopril (30 mg/kg/day) or losartan (15 mg/kg/day) for 30 days. ACE activity was determined in right (RV) and left ventricular (LV) muscles and in the scar tissue. The effects of captopril therapy was also investigated in the hydroxiproline (OH-Pro) and protein in RV and LV.

RESULTS

ACE activity increased 25% in the RV and 70% in the remaining LV muscle. The highest ACE activity was found in the scar tissue, where it was 4.5 times the value of the LV muscle (420 +/- 68 vs 94 +/- 8 nmoles/g/min; P < 0.01). An increase of the end-diastolic pressure and of the muscle mass was found in the RV and LV of MI rats. Captopril and losartan treatments were equally efficient to attenuate these parameters in both ventricles. Captopril also reduced the total OH-Pro content in the RV and LV muscles. The Prot concentration was significantly reduced in the myocardium of MI rats, an effect enhanced by captopril therapy.

CONCLUSION

The AII concentration in the blood draining from the scar to the surrounding muscle is probably high. It is likely that this elevated local generation of AII contributes to hypertrophy and to collagen deposition. The effects of ACE inhibitors on remodeling are likely to depend on the reduction of the locally generated AII.