Editing Strength training (section)

== Aerobic exercise versus anaerobic exercise ==
{{See also|Anaerobic exercise}}
Strength training exercise is primarily [[anaerobic exercise|anaerobic]].<ref name="kraemer">{{cite journal | vauthors = Kraemer WJ | title = Strength training basics: designing workouts to meet patients' goals | journal = The Physician and Sportsmedicine | volume = 31 | issue = 8 | pages = 39–45 | date = August 2003 | pmid = 20086485 | doi = 10.3810/psm.2003.08.457 | s2cid = 5384504 }}</ref> Even while training at a lower intensity (training loads of ≈20-RM), [[anaerobic glycolysis]] is still the major source of power, although [[aerobic exercise|aerobic]] metabolism makes a small contribution.<ref>{{cite journal | vauthors = Knuttgen HG | title = What is exercise? A primer for practitioners | journal = The Physician and Sportsmedicine | volume = 31 | issue = 3 | pages = 31–49 | date = March 2003 | pmid = 20086460 | doi = 10.1080/00913847.2003.11440567 | s2cid = 58736006 }}</ref> Weight training is commonly perceived as anaerobic exercise, because one of the more common goals is to increase strength by lifting heavy weights. Other goals such as rehabilitation, weight loss, body shaping, and bodybuilding often use lower weights, adding aerobic character to the exercise.

Except in the extremes, a muscle will fire fibres of both the aerobic or anaerobic types on any given exercise, in varying ratio depending on the load on the intensity of the contraction.<ref name="kraemer"/> This is known as the energy system continuum. At higher loads, the muscle will recruit all muscle fibres possible, both anaerobic ("fast-twitch") and aerobic ("slow-twitch"), to generate the most force. However, at maximum load, the anaerobic processes contract so forcefully that the aerobic fibers are completely shut out, and all work is done by the anaerobic processes. Because the anaerobic muscle fibre uses its fuel faster than the blood and intracellular restorative cycles can resupply it, the maximum number of repetitions is limited.<ref>{{Cite news|url=https://www.dynamicchiropractic.com/mpacms/dc/article.php?id=31599|title=Muscle Metabolism: Aerobic vs. Anaerobic| vauthors = Griner T |year=2000|work=[[Dynamic Chiropractic]]|issue=7|volume=18}}</ref> In the aerobic regime, the blood and intracellular processes can maintain a supply of fuel and oxygen, and continual repetition of the motion will not cause the muscle to fail.

Circuit weight training is a form of exercise that uses a number of weight training exercise sets separated by short intervals. The cardiovascular effort to recover from each set serves a function similar to an aerobic exercise, but this is not the same as saying that a weight training set is itself an aerobic process.

Strength training is typically associated with the production of lactate, which is a limiting factor of exercise performance. Regular endurance exercise leads to adaptations in skeletal muscle which can prevent lactate levels from rising during strength training. This is mediated via activation of [[PGC-1alpha]] which alter the LDH (lactate dehydrogenase) isoenzyme complex composition and decreases the activity of the lactate generating enzyme LDHA, while increasing the activity of the lactate metabolizing enzyme LDHB.<ref>{{cite journal | vauthors = Summermatter S, Santos G, Pérez-Schindler J, Handschin C | title = Skeletal muscle PGC-1α controls whole-body lactate homeostasis through estrogen-related receptor α-dependent activation of LDH B and repression of LDH A | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 110 | issue = 21 | pages = 8738–43 | date = May 2013 | pmid = 23650363 | pmc = 3666691 | doi = 10.1073/pnas.1212976110 | bibcode = 2013PNAS..110.8738S | doi-access = free }}</ref>