We may have been underestimating the way our blood supply supports muscles during exercise, say scientists

An improved vascular system – the way blood is directed around the body - could help to maximise benefits through exercise, according to new research.

Researchers have found that our metabolism during exercise has sufficient capacity to accommodate the demands of increased activity, but that muscles are unable to realise their full potential to sustain exercise without additional support. 

Improving the way blood flow transfers oxygen and removes waste from our muscles could therefore be the key to supporting our body through exercise. 

Data from the study also suggests that the arrangement of our capillaries – tiny blood vessels that connect arteries to veins within muscles - could be more important than density. 

This means that the process of tissue remodelling needs to be controlled on an exceptionally fine scale to optimise oxygen delivery, i.e. demanding quality over quantity. 

What happens to our bodies during exercise 

Our body reacts to exercise in a complex way. 

Our breathing, metabolism, muscles, and cardiovascular system – including the vessels that deliver blood-borne nutrients around the body – are all activated. Other systems, such as our digestive system reduce activity to allow the body to exercise more efficiently. 

With so many systems upregulating their function, it’s hard to know which one is contributing most to enhance exercise performance.

This detail must be better understood to effectively develop personalised exercise plans. 
The study 

As exercise involves a complex interaction of factors, it’s difficult to tease out this detail through studying exercise alone. 

Instead, researchers at the University of Leeds have used several approaches to test different elements of the response in isolation. In this case, researchers used a technique called indirect electric stimulation (ES) where motor nerves are excited by implantable devices to recruit muscle fibres. 

During the experiment, researchers used ES to replicate the effect of exercise at different rates in sleeping rats. Researchers observed that ES encouraged change in the amount and distribution of muscle capillaries but did not change the muscle metabolism, emphasising the importance of capillary supply in promoting exercise tolerance. 

Although the study was carried out in rats, human systems are set up in a similar way, so the same results are likely to be seen. 

Dr Roger Kissane, Postdoctoral Research Associate at University of Liverpool and previous researcher at University of Leeds when this research was conducted, said:

“This work highlights the complex interplay between capillaries and muscle metabolism. Simply having more capillaries does not mean your muscle will have a greater functional capacity, the location of these small blood vessels within the muscle appears to be an important determinant of muscle function.”

Professor Stuart Egginton, Professor of Exercise Science at University of Leeds said: 

“We know that exercise has a multitude of benefits, with current research strongly indicating that exercise isn’t a “one size fits all” system. An endurance athlete training for a marathon and a person with arthritis recovering from surgery, for example, will need different exercise plans to reach their desired outcome.

Understanding how our different bodily systems are at play during exercise is a crucial part of that puzzle.

The paper, “Skeletal muscle adaptation to indirect electrical stimulation: divergence between microvascular and metabolic adaptations” is published in The Physiological Society and is funded by the British Heart Foundation and Wellcome Trust.