In addition to a pair of sore legs, new research from University of Auckland in New Zealand suggests that cycling may also have the effect of straining the eyes as well. But don't set aside the kickstand just yet: the study also found that drinking coffee might help to prevent such an effect.
Researchers explain that vigorous exercise can lower the central nervous system's ability to drive muscle function, resulting in what is known as central fatigue. For example, prolonged cycling can trigger central fatigue, which is normally experienced through tiring of the legs.
But while it is well established that central fatigue affects limb movement, Dr. Nicholas Gant and his colleagues noted that it is unclear whether it impacts other motor systems, such as eye movement.
For the study, Dr. Gant and his team enrolled 11 well-trained cyclists, who cycled using exercise bikes for 3 hours just to find out!
The caffeine can indirectly boost the activity of certain neurotransmitters - chemicals that relay signals between brains cells - and previous studies have suggested that impairments in neurotransmitter activity might be responsible for central fatigue, researchers explain.
Some participants consumed caffeine during their 3-hour cycling session - a dose equivalent to two cups of coffee - while the remaining subjects consumed a decaffeinated placebo solution. Researchers tested their eye movement using a head-fixed eye-tracking system once participants had finished cycling.
Caffeine restored impaired eye movement
Researchers found that the strenuous exercise among participants caused a neurotransmitter imbalance, which slowed down the subjects' rapid eye movements.
"Interestingly, the areas of the brain that process visual information are robust to fatigue. It's the pathways that control eye movements that seem to be our weakest link," says Dr. Gant.
The researchers found that participants who consumed the caffeinated beverages saw their neurotransmitter balance restored, which improved their rapid eye movements. No such effect was found among subjects who drank the decaffeinated solution.
"These results are important because our eyes must move quickly to capture new information," he adds. "But there's hope for coffee drinkers because this visual impairment can be prevented by consuming caffeine." says Dr. Gant.
The researchers are now in the process of investigating whether psychiatric drugs - which work by restoring neurotransmitter levels - might be effective for treating fatigue caused by strenuous exercise.