Complex sentence: This is done by constricting the capillaries from the muscles to the veins, but a longer recovery time is needed, though, which in the long run may be less efficient than quicker, aerobic metabolic dives.
Split into simpler sentences: This is done by constricting the capillaries going from the muscles to the veins. This requires a longer recovery time though, which in the long run, may be less efficient than quicker, aerobic metabolic dives.