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ROS/RNS-related adaptations of skeletal muscles to aerobic exercise
No full textCellular metabolic processes produce Reactive Oxygen and Nitrogen Species (ROS/RNS) in small amounts in the course of normal activities. In skeletal muscle ROS/RNS production is greatly enhanced by contractile activity (1). Aerobic exercise training is known to induce a number of relevant adaptations in skeletal muscle, including fiber-type and metabolic shift of fast-twitch/glycolytic fibers towards a more fatigue-resistant and oxidative phenotype (2,3). On the other hand, excess ROS/RNS production is potentially damaging (4). Aim of the present work was to evaluate which adaptations are induced by moderate aerobic training in two opposite types of muscle cells: Tibialis Anterior (fast-twitch/glycolytic) and Soleus (slow-twitch/oxidative), with special attention to ROS/RNS-induced or -regulated pathways. Moreover, we intended to examine whether moderate exercise training caused ROS/RNS-related damages and/or activated defensive responses. Experimentation was carried out on 12 young male Sprague-Dowley rats which were gradually trained to run on a treadmill 1hr/day, 3 times/week, 14 weeks and reached ~60% VO2max at the end of training.
Unexpectedly, training-induced ROS/RNS signaling promoted cell proliferation in both types of muscle cells; the small consequent redox unbalance activated, rather than inhibited, calcium-handling molecules and channels. Moderate exercise training was not damaging, probably because anti-oxidant and cytoprotective mechanisms were induced, however some oxidative stress markers appeared. Relevant results are summarized in the diagram below.
References:
1. McArdle A et al. Am. J Physiol Cell Physiol 2001; 280: C621-C627.
2. Flück M, Hoppeler H.. Rev Physiol Biochem Pharmacol 2003; 146: 159-216.
3. Marini M, Veicsteinas A. European Journal Translational Myology - Myology Reviews 2010; 20: 113-128.
4. Sahlin K et al. J Appl Physiol 2010; 108: 780-787
Exercise: friend and foe
No full textPhysical activity is probably the only physiological source of increased production of ROS. How can we reconcile this evidence with the known beneficial effects of exercise? We will present here some of the results obtained in a multicentric study carried out on rats undergoing aerobic exercise training on a treadmill. Exercise – even moderate - led to the formation of long-lasting circulating lipid peroxidation products and to DNA damage in male germ cells. On the other hand, exercise training protected rat heart from ischemia/reperfusion (I/R) injury; both oxidative stress and cardioprotection were proportional to the intensity of the exercise protocol. Training-induced cardioprotection was accompained by the upregulation of Mn-SOD, HSP70 and HO-1 in the heart, along with the upregulation of other proteins, such as Caveolin-3, probably unrelated to the anti-oxidant defence. A 10-wk exercise training led to the sprouting of new capillaries in the myocardium. Both heart resistance to I/R injury, and increase in HSP70 protein and in cardiac vascularization were rather persistant over a detraining period. Moreover, physical training induced paraoxonase-3 upregulation, thus contributing to reduce cholesterol oxidation. Some of the biochemical pathways leading to these beneficial effects were elucidated in our work. Noteworthy, physical activity appeared to exert an hormetic effect, with chronic moderate exercise upregulating protective proteins, and single bursts of stressing exercise leading to cell injury, expecially in untrained animals. The contribute of ROS to the signaling pathways leading to the upregulation of cell defences as well as to cell damage is paramount
The exercised skeletal muscle: a review
Full text linkThe skeletal muscle is the second more plastic tissue of the body - second to the nervous tissue only. In fact, both physical activity and inactivity contribute to modify the skeletal muscle, by
continuous signaling through nerve impulses, mechanical stimuli and humoral clues. In turn, the skeletal muscle sends signals to the body, thus contributing to its homeostasis. We'll review
here the contribute of physical exercise to the shaping of skeletal muscle, to the adaptation of its mass and function to the different needs imposed by different physical activities and to the
attainment of the health benefits associated with active skeletal muscles. Focus will primarily be on the molecular pathways and on gene regulation that result in skeletal muscle adaptation
to exercise
HEART RATE VARIABILITY AND AUTONOMIC ACTIVITY AT REST AND DURING EXERCISE IN VARIOUS PHYSIOLOGICAL CONDITIONS
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Influence of low and high dietary fat on physical performance in untrained males.
No full textPURPOSE:
Dietary manipulations have been used in athletes to enhance aerobic performance. We intended to verify whether the quality of energy substrate provided by food (percentage of total calories from fat and carbohydrates) per se has the ability to affect aerobic performance in sedentary humans.
METHOD:
Fourteen healthy sedentary males were sequentially submitted to 4-wk eucaloric diets (spontaneous diet: 30% of total calories from fat; low-fat, 15% fat; high-fat, 55% fat; and spontaneous, 30% fat). After each diet period, individual body mass, percentage body fat (plicometry), VO2max (incremental bicycle-ergometry) and endurance (pedaling time to exhaustion at 75%VO2max) were measured. VO2, VCO2, VE, R, and heart rate (HR) were measured at rest and during exercise tests. Body composition and performance data (VO2max and endurance) were compared for significant differences by repeated measures ANOVA.
RESULTS:
Subjects' body weight, percentage body fat, and fitness status (indicated by intercept and slope of the HR/VO2 linear relationship) did not change significantly during the study, thus ruling out the influence of these potential confounders. For a given workload, VO2, VE, and R were unaffected by diet composition. VO2max and endurance time were not significantly modified by the different diets.
CONCLUSIONS:
Our study showed no impact, positive or negative, of diet's macronutrient composition on physical performance. It appears that the quality of energy substrate provided by food does not have the ability to affect either maximal or submaximal aerobic performance in untrained individual
Mechanisms of blood pressure and heart rate variability: an insight from low-level paraplegia.
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