Today I rode my bike through the widespread green prairie of South Quad here at Notre Dame. The expanse of thin and evenly tall blades of grass is sliced by strips of smooth concrete, which streak across its surface. Except, of course, that concrete is not really smooth. If you’ve ever (1) reached and dragged your hand across concrete paths or (2) crashed and dragged your body across the concrete, then you intrinsically know that even seemingly smooth paths have texture.
And when you ride over any textured terrain, your tire experiences consecutive minute vertical displacements–aka vibrations–and then your frame experiences these vibrations, and then your handlebars experience these vibrations, and then YOU experience these vibrations in your hands and feet. Advanced riders agree on two things about vibrations: they help you “feel” the texture of the trail, which improves control and confidence, and severe vibrations punish your forearms with lactic acid buildup, which increases fatigue. But how do vibrations affect the average rider on sidewalks and paths? How do they affect your muscular fatigue and performance in your extremities (arms/legs)? Because every time you ride a bike, you’re experiencing vibrations.
To this end, Marchand et al. examined rider perception of effort under short 3-minute cycling bouts, with and without vibrational stimulus on the Achilles tendon before performing the cycling bout. The Achilles tendon is on the back of the heel and can be seen in the photo below. They measured power output, heart rate, and electrical activity of the vastus lateralis muscle, a large muscle on your quad on the outside of the thigh. From this, they observed that vibrations interrupt the nervous system signalling that work was done to the brain, causing the brain to underestimate the amount of work done, thus allowing you to push harder. So, for the short-distance commuter across campus where everything is a 3-5 minute bike ride, it follows that the slight vibration you feel actually decreases your fatigue, helping you arrive at class well poised to learn.
Further diving into the nervous system, we consider Hsu et al., who explored longer cycling times and a more sedentary patient population. In this case, there’s more nuance in when the nervous system engages: We see that lower resistance over longer ranges stresses the nervous system more, whereas higher resistance in short time frames stresses the musculoskeletal frame and leads to double the Rate of Perceived Exertion (RPE) in half the time frame! If you’re trying to arrive at class without being out of breath, better to leave a few minutes early and go slightly slower than to stand and mash the pedals.
Finally, Askit et al. created the most realistic scenario for an athletic cyclist, wherein they recruited eight male mountain cyclists and ran 30-minute mountain bike trials, with attached vibration modules on the body enabled or disabled. They measured oxygen volume inhalation, carbon dioxide exhalation, heart rate, RPE, and gross efficiency. Here, we see that vibration also improved gross efficiency, though it failed to appreciably improve any of the other parameters. The athletes felt the same RPE but did more work: we see the disconnect again!
In conclusion, we see that the vibrations you feel while riding reduce nervous system communication from extremities back to the central nervous system, which leads to a disconnect of how much work has been done, thus favoring increased performance as it disrupts the governing feedback loop where the body tells itself to slow down. So, next time you feel a little buzz in the bars, remember to enjoy that they are keeping you fresh longer, and enjoy the ride.