It seems that the creators of the popular cartoon character Popeye were right all along - eat spinach and you really will get big biceps.

Research from Swedish medical university the Karolinska Institute shows that the mitochondria - the cellular power producers of muscles - are boosted by nitrate, a substance that is abundant in spinach and other vegetables such as beetroot and lettuce.

In the study, healthy people took the nitrate equivalent to 200-300g of spinach for three days, while another group took a placebo. Following this, both sets of participants were asked to perform a cycling task.

Samples from thigh muscles were taken and compared and it was found that after the nitrate ingestion a significant improvement was seen in the mitochondria.

The mitochondria in the nitrate group consumed less oxygen and more ATP – an energy rich substance.