Calf muscle oxygen saturation and the effects of supervised exercise training for intermittent claudication

Abstract

Supervised exercise training is not associated with increased gastrocnemius muscle oxygenation during exercise or increased hyperemic hemoglobin flow after a model of ischemia. This suggests that the symptomatic improvement witnessed is not the result of increased oxygen delivery to the active muscle. The enhanced recovery after exercise training therefore reflects a combination of enhanced metabolic economy and increased oxidative capacity, suggesting that exercise training helps reverse an acquired metabolic myopathy.

Characterising skeletal muscle haemoglobin saturation during exercise using near-infrared spectroscopy in chronic kidney disease

“…As such, the working muscles require an adequate supply so that O 2 exceeds (or at least matches) demand. As expected, during incremental exercise, we observed a steady decline in SMO 2 % representing an imbalance between supply and utilization [34]. Pertinently, once patients reached a nadir in SMO 2 %, cessation of the test quickly followed due to fatigue and/or inability to keep pace with the test.…”

“…This minimum value reportedly occurs as maximal aerobic capacity (i.e., VO 2 peak/max) is neared or reached [35–37]. This response has been observed in other studies (e.g., [34–37, 46–48]).…”

“…Along with delayed SMO 2 % recovery, the rate of SMO 2 % decline during exercise is also a key parameter in muscle O 2 metabolism [23, 24]. During progressive exercise, a steady decline in SMO 2 % represents an imbalance between supply and utilization [34]. The minimum SMO 2 % reached occurs at/near maximum exercise capacity [35–37], and the observed time to reach the minimum SMO 2 % has been shown to be more pronounced in PAD [24], chronic heart failure (CHF) [36], and COPD [37] patients compared to controls.…”

Sildenafil improves skeletal muscle oxygenation during exercise in men with intermittent claudication

“…Of note, few therapeutic strategies to date have been shown to effectively improve muscle oxygenation during exercise in patients with IC. For example, Beckitt et al (6) recently reported that angioplasty, but not supervised exercise training, modestly improved gastrocnemius muscle oxygenation during submaximal exercise in claudicants (6). In the present study, we observed that sildenafil reduced ⌬[DeoxyHbϩMb] by ϳ40% relative to the placebo condition during the graded treadmill test (Fig.…”

“…An alternative explanation is that the magnitude of the improvement in muscle oxygenation evoked by sildenafil was insufficient to be translated into a measurable change in walking tolerance. However, this seems unlikely as the improvement observed herein is comparable to that achieved after angioplasty (6), which typically enhances walking tolerance in patients with IC (6,62). Lastly, it is worth highlighting that NIRS measurements were performed in a single site in the gastrocnemius muscle, and it is unclear whether the observed local improvement in microvascular O 2 delivery-to-utilization matching after sildenafil extends to the other regions of the muscle, as well as to other muscles in the leg recruited during walking.…”