Effects of recovery mode on performance, O2 uptake, and O2 deficit during high-intensity intermittent exercise

[EN] The aim of this study was to determine the influence of activity performed during the recovery period on the aerobic and anaerobic energy yield, as well as on performance, during high-intensity intermittent exercise (HIT). Ten physical education students participated in the study. First they underwent an incremental exercise test to assess their maximal power output (Wmax) and VO2max. On subsequent days they performed three different HITs. Each HIT consisted of four cycling bouts until exhaustion at 110% Wmax. Recovery periods of 5 min were allowed between bouts. HITs differed in the kind of activity performed during the recovery periods: pedaling at 20% VO2max (HITA), stretching exercises, or lying supine. Performance was 3-4% and aerobic energy yield was 6-8% (both p < 0.05) higher during the HITA than during the other two kinds of HIT. The greater contribution of aerobic metabolism to the energy yield during the high-intensity exercise bouts with active recovery was due to faster VO2 kinetics (p< 0.01) and a higher VO2peak during the exercise bouts preceded by active recovery (p < 0.05). In contrast, the anaerobic energy yield (oxygen deficit and peak blood lactate concentrations) was similar in all HITs. Therefore, this study shows that active recovery facilitates performance by increasing aerobic contribution to the whole energy yield turnover during high-intensity intermittent exercise.

Skeletal muscle mitochondrial DNA content in exercising humans

[EN] Several weeks of intense endurance training enhances mitochondrial biogenesis in humans. Whether a single bout of exercise alters skeletal muscle mitochondrial DNA (mtDNA) content remains unexplored. Double-stranded mtDNA, estimated by slot-blot hybridization and real time PCR and expressed as mtDNA-to-nuclear DNA ratio (mtDNA/nDNA) was obtained from the vastus lateralis muscle of healthy human subjects to investigate whether skeletal muscle mtDNA changes during fatiguing and nonfatiguing prolonged moderate intensity [2.0-2.5 h; approximately 60% maximal oxygen consumption (Vo(2 max))] and short repeated high-intensity exercise (5-8 min; approximately 110% Vo(2 max)). In control resting and light exercise (2 h; approximately 25% Vo(2 max)) studies, mtDNA/nDNA did not change. Conversely, mtDNA/nDNA declined after prolonged fatiguing exercise (0.863 +/- 0.061 vs. 1.101 +/- 0.067 at baseline; n = 14; P = 0.005), remained lower after 24 h of recovery, and was restored after 1 wk. After nonfatiguing prolonged exercise, mtDNA/nDNA tended to decline (n = 10; P = 0.083) but was reduced after three repeated high-intensity exercise bouts (0.900 +/- 0.049 vs. 1.067 +/- 0.071 at baseline; n = 7; P = 0.013). Our findings indicate that prolonged and short repeated intense exercise can lead to significant reductions in human skeletal muscle mtDNA content, which might function as a signal stimulating mitochondrial biogenesis with exercise training.

Corpus-based teaching of pragmatics

[EN]This paper is a proposal for teaching pragmatics following a corpus-based approach. Corpora have had a high impact on how linguistics is looked at these days. However, teaching linguistics is still traditional in its scope and stays away from a growing tendency of incorporating authentic samples in the theoretical classroom, and so lecturers perpetuate the presentation of the same canonical examples students may find in their textbooks or in other introductory monographs. Our view is that using corpus linguistics, especially corpora freely available in the World Wide Web, will result in a more engaging and fresh look at the course of Pragmatics, while promoting early research in students. This way, they learn the concepts but most importantly how to later identify pragmatic phenomena in real text. Here, we raise our concern with the methodology, presenting clear examples of corpus-based pragmatic activities, and one clear result is the fact that students learn also how to be autonomous in their analysis o f data. In our proposal, we move from more controlled tasks to autonomy. This proposal focuses on students enrolled in the course Pragmática de la Lengua inglesa, currently part of the curriculum in Lenguas Modernas, Universidad de Las Palmas de Gran Canaria.

Maximal exercise and muscle oxygen extraction in acclimatizing lowlanders and high altitude natives

[EN] The tight relation between arterial oxygen content and maximum oxygen uptake (Vv(o2max)within a given person at sea level is diminished with altitude acclimatization. An explanation often suggested for this mismatch is impairment of the muscle O(2) extraction capacity with chronic hypoxia, and is the focus of the present study. We have studied six lowlanders during maximal exercise at sea level (SL) and with acute (AH) exposure to 4,100 m altitude, and again after 2 (W2) and 8 weeks (W8) of altitude sojourn, where also eight high altitude native (Nat) Aymaras were studied. Fractional arterial muscle O(2) extraction at maximal exercise was 90.0+/-1.0% in the Danish lowlanders at sea level, and remained close to this value in all situations. In contrast to this, fractional arterial O(2) extraction was 83.2+/-2.8% in the high altitude natives, and did not change with the induction of normoxia. The capillary oxygen conductance of the lower extremity, a measure of oxygen diffusing capacity, was decreased in the Danish lowlanders after 8 weeks of acclimatization, but was still higher than the value obtained from the high altitude natives. The values were (in ml min(-1) mmHg(-1)) 55.2+/-3.7 (SL), 48.0+/-1.7 (W2), 37.8+/-0.4 (W8) and 27.7+/-1.5 (Nat). However, when correcting oxygen conductance for the observed reduction in maximal leg blood flow with acclimatization the effect diminished. When calculating a hypothetical leg V(o2max)at altitude using either the leg blood flow or the O(2) conductance values obtained at sea level, the former values were almost completely restored to sea level values. This would suggest that the major determinant V(o2max)for not to increase with acclimatization is the observed reduction in maximal leg blood flow and O(2) conductance.

Muscular and pulmonary O2 uptake kinetics during moderate- and high-intensity sub-maximal knee-extensor exercise in humans

[EN] The purpose of this investigation was to determine the contribution of muscle O(2) consumption (mVO2) to pulmonary O(2) uptake (pVO2) during both low-intensity (LI) and high-intensity (HI) knee-extension exercise, and during subsequent recovery, in humans. Seven healthy male subjects (age 20-25 years) completed a series of LI and HI square-wave exercise tests in which mVO2 (direct Fick technique) and pVO2 (indirect calorimetry) were measured simultaneously. The mean blood transit time from the muscle capillaries to the lung (MTTc-l) was also estimated (based on measured blood transit times from femoral artery to vein and vein to artery). The kinetics of mVO2 and pVO2 were modelled using non-linear regression. The time constant (tau) describing the phase II pVO2 kinetics following the onset of exercise was not significantly different from the mean response time (initial time delay + tau) for mVO2 kinetics for LI (30 +/- 3 vs 30 +/- 3 s) but was slightly higher (P < 0.05) for HI (32 +/- 3 vs 29 +/- 4 s); the responses were closely correlated (r = 0.95 and r = 0.95; P < 0.01) for both intensities. In recovery, agreement between the responses was more limited both for LI (36 +/- 4 vs 18 +/- 4 s, P < 0.05; r = -0.01) and HI (33 +/- 3 vs 27 +/- 3 s, P > 0.05; r = -0.40). MTTc-l was approximately 17 s just before exercise and decreased to 12 and 10 s after 5 s of exercise for LI and HI, respectively. These data indicate that the phase II pVO2 kinetics reflect mVO2 kinetics during exercise but not during recovery where caution in data interpretation is advised. Increased mVO2 probably makes a small contribution to during the first 15-20 s of exercise.

Exercise and bone mass in adults

[EN] There is a substantial body of evidence indicating that exercise prior to the pubertal growth spurt stimulates bone growth and skeletal muscle hypertrophy to a greater degree than observed during growth in non-physically active children. Bone mass can be increased by some exercise programmes in adults and the elderly, and attenuate the losses in bone mass associated with aging. This review provides an overview of cross-sectional and longitudinal studies performed to date involving training and bone measurements. Cross-sectional studies show in general that exercise modalities requiring high forces and/or generating high impacts have the greatest osteogenic potential. Several training methods have been used to improve bone mineral density (BMD) and content in prospective studies. Not all exercise modalities have shown positive effects on bone mass. For example, unloaded exercise such as swimming has no impact on bone mass, while walking or running has limited positive effects.

Pulmonary gas exchange at maximal exercise in Danish lowlanders during 8 wk of acclimatization to 4,100 m and in high-altitude Aymara natives

[EN] We aimed to test effects of altitude acclimatization on pulmonary gas exchange at maximal exercise. Six lowlanders were studied at sea level, in acute hypoxia (AH), and after 2 and 8 wk of acclimatization to 4,100 m (2W and 8W) and compared with Aymara high-altitude natives residing at this altitude. As expected, alveolar Po2 was reduced during AH but increased gradually during acclimatization (61 +/- 0.7, 69 +/- 0.9, and 72 +/- 1.4 mmHg in AH, 2W, and 8W, respectively), reaching values significantly higher than in Aymaras (67 +/- 0.6 mmHg). Arterial Po2 (PaO2) also decreased during exercise in AH but increased significantly with acclimatization (51 +/- 1.1, 58 +/- 1.7, and 62 +/- 1.6 mmHg in AH, 2W, and 8W, respectively). PaO2 in lowlanders reached levels that were not different from those in high-altitude natives (66 +/- 1.2 mmHg). Arterial O2 saturation (SaO2) decreased during maximum exercise compared with rest in AH and after 2W and 8W: 73.3 +/- 1.4, 76.9 +/- 1.7, and 79.3 +/- 1.6%, respectively. After 8W, SaO2 in lowlanders was not significantly different from that in Aymaras (82.7 +/- 1%). An improved pulmonary gas exchange with acclimatization was evidenced by a decreased ventilatory equivalent of O2 after 8W: 59 +/- 4, 58 +/- 4, and 52 +/- 4 l x min x l O2(-1), respectively. The ventilatory equivalent of O2 reached levels not different from that of Aymaras (51 +/- 3 l x min x l O2(-1)). However, increases in exercise alveolar Po2 and PaO2 with acclimatization had no net effect on alveolar-arterial Po2 difference in lowlanders (10 +/- 1.3, 11 +/- 1.5, and 10 +/- 2.1 mmHg in AH, 2W, and 8W, respectively), which remained significantly higher than in Aymaras (1 +/- 1.4 mmHg). In conclusion, lowlanders substantially improve pulmonary gas exchange with acclimatization, but even acclimatization for 8 wk is insufficient to achieve levels reached by high-altitude natives.

Parasympathetic neural activity accounts for the lowering of exercise heart rate at high altitude

[EN] BACKGROUND: In chronic hypoxia, both heart rate (HR) and cardiac output (Q) are reduced during exercise. The role of parasympathetic neural activity in lowering HR is unresolved, and its influence on Q and oxygen transport at high altitude has never been studied. METHODS AND RESULTS: HR, Q, oxygen uptake, mean arterial pressure, and leg blood flow were determined at rest and during cycle exercise with and without vagal blockade with glycopyrrolate in 7 healthy lowlanders after 9 weeks' residence at >/=5260 m (ALT). At ALT, glycopyrrolate increased resting HR by 80 bpm (73+/-4 to 153+/-4 bpm) compared with 53 bpm (61+/-3 to 114+/-6 bpm) at sea level (SL). During exercise at ALT, glycopyrrolate increased HR by approximately 40 bpm both at submaximal (127+/-4 to 170+/-3 bpm; 118 W) and maximal (141+/-6 to 180+/-2 bpm) exercise, whereas at SL, the increase was only by 16 bpm (137+/-6 to 153+/-4 bpm) at 118 W, with no effect at maximal exercise (181+/-2 bpm). Despite restoration of maximal HR to SL values, glycopyrrolate had no influence on Q, which was reduced at ALT. Breathing FIO(2)=0.55 at peak exercise restored Q and power output to SL values. CONCLUSIONS: Enhanced parasympathetic neural activity accounts for the lowering of HR during exercise at ALT without influencing Q. The abrupt restoration of peak exercise Q in chronic hypoxia to maximal SL values when arterial PO(2) and SO(2) are similarly increased suggests hypoxia-mediated attenuation of Q.