8,101
edits
Changes
From Fellrnr.com, Running tips
no edit summary
* The stroke volume (blood pumped with each beat) also increases. The volume is greater at rest and during exercise, with the stroke volume in a highly trained athlete twice that of an untrained person. This increase is due to multiple factors:
** The increased heart size.
** A slower heart rate [[Heart Rate]] for a given exercise level which allows more time for the heart to fill.
** Increased total blood volume.
** A greater force of contraction.
** A lower volume of blood remaining in the heart after contraction.
* [[Resting Heart Rate| Resting Heart Rate]] drops with training. A sedentary person with a resting heart rate [[Heart Rate]] of 80 BPM may be able to reduce their resting heart rate [[Heart Rate]] by 1 BPM per week of training for up to 10 weeks, though some studies have shown much smaller changes (5 BPM over 20 weeks). * The [[Heart Rate| Heart Rate]] for a given exercise intensity is reduced, and sedentary people undergoing 6 months of training can reduce the heart rate [[Heart Rate]] for a given intensity by 10-30 BPM.
* [[Maximum Heart Rate| Maximum Heart Rate]] does not typically change with endurance training, but several studies have suggested that sedentary people with a Max HR of 180+ BPM may have a slightly reduced value post-training. This reduction in Max HR may be to preserve the time for the heart to refill with blood. Also, older athletes may have less of an age related decline in Max HR than those that are sedentary.
* Cardiac output at rest and at moderate intensity exercise remains largely unchanged with training, which is the result of a greater stroke volume at a lower heart rate[[Heart Rate]]. (Sometimes the cardiac output will be slightly lower, probably due to greater oxygen extraction by the muscles.) However, at higher intensity exercise the cardiac output is increased, which results in improved performance.
=Circulation Adaptations=
* Endurance training results in an increased number of capillaries in the muscles. The ratio of capillaries to muscle fibers allows for a greater delivery of blood to the working muscles. In addition, the use of existing capillaries is improved with training.
=Lung (pulmonary) Adaptations=
* Generally, there is little structural adaptation of the lungs, as their capacity is far greater than is needed in most individuals.
* [[Breathing ]] at rest is unchanged with training, but for a given sub-maximal intensity, breathing [[Breathing]] is reduced by as much as 20-30%. Maximal breathing [[Breathing]] increases with training, with increases in both the breathing [[Breathing]] rate and volume.
* In some highly trained athletes the lungs are unable to keep up at high exercise intensities and the blood oxygen saturation ([[SpO2|SpO<sub>2</sub>]]) can drop.
* Training increases the blood flow to the lungs (perfusion), which combined with greater breathing [[Breathing]] and lower oxygen saturation of the blood entering the lungs results in a greater uptake of oxygen (pulmonary diffusion).
=Muscular Adaptations=
* One of the most important adaptations to endurance training is the increase in the number of capillaries in the muscles.
* Endurance training may increase the size of slow twitch (Type I) muscle fibers by up to 25%, or the training may decrease the size of slow twitch and some fast twitch (Type IIa) fibers<ref name="Trappe-2006">S. Trappe, M. Harber, A. Creer, P. Gallagher, D. Slivka, K. Minchev, D. Whitsett, Single muscle fiber [[Fiber]] adaptations with marathon training., J Appl Physiol, volume 101, issue 3, pages 721-7, Sep 2006, doi [http://dx.doi.org/10.1152/japplphysiol.01595.2005 10.1152/japplphysiol.01595.2005], PMID [http://www.ncbi.nlm.nih.gov/pubmed/16614353 16614353]</ref>.
* There are changes within the fast twitch fibers so that Type IIb/IIx become more like Type IIa with endurance training. There is some evidence of a small change of fast twitch fibers to slow twitch.
* Oxygen is carried within a muscle fiber [[Fiber]] by myoglobin, which is similar to hemoglobin. Endurance training can increase the myoglobin in muscle fibers by up to 80%.
* The size and number of mitochondria in the muscles increases with training. In rats, 27 weeks of exercise increased the mitochondria size by 35% and the number by 15%.
* Within the mitochondria, the oxidative enzymes increase with training. Over 7 months of swim training, one oxidative enzyme ([http://en.wikipedia.org/wiki/Succinate_dehydrogenase SDH]) increased by 800%.
= Adaptations and Endurance Running=
[[File:Model of endurance running.jpg|none|thumb|500px|A model of how three adaptations impact endurance performance<ref name="Midgley-2007"/>.]]
This flowchart shows that while [[VO2max|V̇O<sub>2</sub>max]] is a key determinant of performance, it interacts with other factors. Lactate threshold defines what percentage of [[VO2max|V̇O<sub>2</sub>max]] can be sustained, which defines the energy available (ATP re-synthesis). [[Running economy Economy]] then defines how well this energy can be translated into forward motion.
=References=
<references>
