Jan Helgerud · Eivind Wang · Mats Peder Mosti · Øystein Nordrum Wiggen · Jan Hoff
Peripheral arterial disease (PAD) is caused by arterial narrowing in the lower extremities because of atherosclerosis and leads to thickening of the arterial wall. This inhibits blood flow to the legs, causing lactic acid formation and impaired walking ability. Symptoms of PAD may vary from intermittent claudication to pain at rest. Intermittent claudication is caused by critical leg ischemia and is the most severe symptom of PAD. Claudication is defined as pain induced by walking which is only relieved by rest. The pain appears in one or both legs during activity and mainly affects the calves, but might also be present in the but- tocks and thighs.
Physical capacity, measured as maximal oxygen consumption (VO2max), is a more powerful predictor of mortality than other established risk factors for cardiovascular disease. Exercise training is known to improve physical capacity, reduce symptoms and slow the progression of PAD. Further, it is shown that the intensity of the training cannot be compensated for by longer duration and that training with high aerobic intensitis shown to be superior to training of low aerobic intensity. Although PAD is localized in the lower extremities it is a manifestation of systemic cardiovascular disease and it is critical to not only provoke training adaptations in peripheral muscle metabolism, but also the overall cardiovascular system. The importance of cardiovascular improvements also becomes evident by the elevated risk of cardiovascular events these patients suffer.
It has been demonstrated that maximal work performed by an isolated small skeletal muscle is not suffcient to tax the oxygen supply components of aerobic endurance. Thus, it seems likely that the calf pain which PAD patients experience restricts them from overloading the cardiovascular system when pursuing exercise training. In practical terms claudication pain in the calf may be seen as the main factor limiting physical capacity in PAD patients.
The training group (n = 10) pursued 8 weeks of high aerobic intensity plantar flexion interval training continued by 8 weeks of high aerobic intensity treadmill training. The control group (n = 11) received advice according to exercise guidelines. Treadmill VO2max and time to exhaustion increased with 17 and 23% during the plantar flexion training period while no changes occurred in the stroke volume of the heart (SV). Following treadmill training, SV increased with 25% while treadmill VO2max and time to exhaustion increased 10 and 16%.
Conclusion: These results demonstrate that the small muscle mass in the leg may limit whole body performance and that training of the small muscle mass on each individual leg is effective for improving whole body exercise performance in PAD patients. These data also suggest that improving calf muscle limitations in PAD patients enhances further cardiovascular improvements when applying whole body exercise.
Read the full study: https://pubmed.ncbi.nlm.nih.gov/19238425/