Also see:
Exercise Induced Stress
Exercise and Effect on Thyroid Hormone
Exercise Induced Menstrual Disorders
Ray Peat, PhD: Quotes Relating to Exercise
Potential Adverse Cardiovascular Effects from Excessive Endurance Exercise
Aspirin and Exercise
Synergistic Effect of Creatine and Baking Soda on Performance
Protective Carbon Dioxide, Exercise, and Performance
Does eccentric training lead to more hypertrophy than concentric training?
“Exercise physiologists, without mentioning functional systems, have recently discovered some principles that extend the discoveries of Meerson and Anokhin. They found that “concentric” contraction, that is, causing the muscle to contract against resistance, improves the muscle’s function, without injuring it. (Walking up a mountain causes concentric contractions to dominate in the leg muscles. Walking down the mountain injures the muscles, by stretching them, forcing them to elongate while bearing a load; they call that eccentric contraction.) Old people, who had extensively damaged mitochondrial DNA, were given a program of concentric exercise, and as their muscles adapted to the new activity, their mitochondrial DNA was found to have become normal.”
“The brain’s role in protecting against injury by stress, when it sees a course of action, has a parallel in the differences between concentric (positive, muscle shortening) and eccentric (negative, lengthening under tension) exercise, and also with the differences between innervated and denervated muscles. In eccentric exercise and denervation, less oxygen is used and less carbon dioxide is produced, while lactic acid increases, displacing carbon dioxide, and more fat is oxidized. Prolonged stress similarly decreases carbon dioxide and increases lactate, while increasing the use of fat.”
“Nerves and muscle cells should be considered together, because they respond to many things in similar ways. The membrane people don’t like to think that nerves have an contractile properties, but in fact they do twitch slightly when stimulated, showing that in the entire cytoplasm that responds to information, not the hypothetical plasma membrane. When they are overstimulated, they swell, as muscles do when they are fatigued. When a muscle is stretched while it’s trying to contract (as in running downhill; this is called “eccentric contraction”) it becomes inflamed, and the structural damage is cumulative. By exercising muscle with “concentric contractions,” allowing them to shorten against resistance, the cellular damage can be repaired.”
“Concentric resistance training has an anabolic effect on the whole body. Sprinting is probably o.k. Endurance exercise is the worst. I don’t think martial arts are necessarily too stressful.”
“Exercise, like aging, obesity, and diabetes, increases the levels of circulating free fatty acids and lactate. But ordinary activity of an integral sort, activates the systems in an organized way, increasing carbon dioxide and circulation and efficiency. Different types of exercise have been identified as destructive or repairative to the mitochondria; “concentric” muscular work is said to be restorative to the mitochondria. As I understand it, this means contraction with a load, and relaxation without a load. The heart’s contraction follows this principle, and this could explain the observation that heart mitochondria don’t change in the course of ordinary aging.”
“Cytochrome oxidase in the brain can also be increased by mental stimulation, learning, and moderate exercise, but excessive exercise or the wrong kind of exercise (“eccentric”) can lower it (Aguiar, et al., 2007, 2008), probably by increasing the stress hormones and free fatty acids. Sedentary living a high altitude has beneficial effects on mitochondria similar to moderate exercise at sea level (He, at al., 2012.”
Mech Ageing Dev. 1987 Aug;39(3):281-8.
Lack of age-dependent changes in rat heart mitochondria.
Manzelmann MS, Harmon HJ.
The effects of aging on the composition and function of cardiac mitochondria from rats exhibiting significant decreases in synaptic brain mitochondria composition and function have been studied. Cytochrome content and cytochrome absorbance wavelength maxima do not change in heart mitochondria. Respiratory activities, respiratory control ratios, ADP/O ratios, and H+/O ratios do not change with increasing age. Unlike in brain synaptic tissue, , energy output of the heart does not decrease with age.
Adv Exp Med Biol. 1995;384:185-94.
Metabolic correlates of fatigue from different types of exercise in man.
Vøllestad NK.
It is well established that muscle fatigue, defined as a decline in maximal force generating capacity, is a common response to muscular activity. To what extent metabolic factors contribute to the reduced muscle function is still debated. Metabolic effects can affect muscle through different processes, either through a reduced ATP supply or by effects on EC-coupling or crossbridge dynamics. Observations from in vitro experiments are often extrapolated to interpret fatigue mechanisms from measurements performed in vivo, without recognizing that the biochemical reactions involved can be quite different depending on such factors as activation pattern, mode and duration of exercise. During repeated submaximal contractions, there is a negligible accumulation of H+ and inorganic phosphate, and hence fatigue must be ascribed to other factors. Substrate depletion might contribute to exhaustion, but cannot explain the gradual loss of maximal force. Curiously, the energetic cost of contraction increases progressively during repeated isometric but not during concentric contractions. With contractions involving high-force or high power output, fatigue is better related to H2PO4- than to pH, but still other factors seem to play a role.
Eur J Appl Physiol. 2012 Apr;112(4):1587-92. Epub 2011 Jul 14.
Similar increases in muscle size and strength in young men after training with maximal shortening or lengthening contractions when matched for total work.
Moore DR, Young M, Phillips SM.
Training exclusively with eccentric (lengthening) contractions can result in greater muscular adaptations than training with concentric (shortening) contractions. We aimed to determine whether training-induced increases in muscle size and strength differed between muscles performing maximal lengthening (LC) or maximal shortening (SC) contractions when total external work is equivalent. Nine healthy young males completed a 9-week isokinetic (0.79 rad/s) resistance training program of the elbow flexors whereby they performed LC with one arm and an equivalent volume of total external work with the contralateral arm as SC. Training increased isometric peak torque for both LC (~10%) and SC (~20%) with no difference (P = 0.14) between conditions. There were also similar increases in isokinetic peak torque at both slow (0.79 rad/s) and fast (5.24 rad/s) shortening and lengthening peak torque for both LC (~8-10%) and SC (~9-20%). Training increased work per repetition similarly for both LC (~17%) and SC (~22%), in spite of ~40% greater work per repetition with LC. The increase in muscle cross-sectional area with training was also similar (P = 0.37) between LC (~6.5%) and SC (~4.6%). We conclude that increases in muscle size and strength with short-term unilateral resistance training are unrelated to muscle contraction type when matched for both exercise intensity (i.e. maximal contractions) and total external work.