Why does cycling cause numbness in the hands?

Many people often take their hands off the handlebars during cycling to eliminate the numbness. Do you want to solve this problem fundamentally? Although I don't have data to know exactly how common cyclists' hand numbness is, I understand that this situation is not uncommon. Hand numbness can usually be alleviated by adjusting the fit of the bicycle.
Let's take a look at the causes of hand numbness during cycling and how to adjust to solve this problem.

Why do hands go numb?

The most common reason for cyclists' hand numbness is that they put too much pressure on the front end of the bicycle. When you put too much pressure on the blood vessels and nerves in your hands, it hinders blood circulation. Inadequate blood flow can cause paresthesia, or numbness, burning, tingling, or "numbness" in the limbs when a part of the body is under too much pressure for a long time. If you can't remove your hands from the handlebars and your chest doesn't lean forward when riding at a moderate intensity, it means that you are bearing too much weight in your hands. Ideally, you should follow the “80/20 rule” where 80% of your weight is on the saddle and 20% is on the front of the bike.

Neck problems can also cause numbness in cyclists’ hands. If your head is tilted forward, riding for long periods will only exacerbate this. Forward head tilt goes hand in hand with rounded shoulders, which can compress your brachial plexus, a network of nerves originating in the neck and upper body portion of the spine, and control movement and sensation in the hands, arms, and shoulders. While intermittent hand numbness is unlikely to have any long-term effects, it’s not something you should ignore.

Impaired sensation in your hands can affect your ability to steer and control your bike, including braking, which can present some serious safety risks. Of course, a comfortable riding experience is more fun. People perform better if they feel comfortable, and their experience is more enjoyable.

Fit issues that cause numbness in your hands

If you experience numbness in your hands while riding, it may be time to reevaluate your bike fit. Here are some of the most common fit-related issues that cause numbness in cyclists’ hands. What’s the best way to deal with them? Find a professional fitter who can assess the overall fit of your bike. But if you can’t find one, I’ve included some tips for adjustment below.

1. Saddle Position

Saddle position is the foundation of bike fit, so if you’re experiencing hand numbness, make sure to look at your saddle position first. When it comes to saddle positioning, the two biggest contributors to hand numbness tend to be before/aft adjustment and saddle tilt. If the saddle is too far forward, it puts more pressure on your hands,
while if the saddle is too far back, it forces you to put pressure on your wrists and elbows, which can cause your head to tilt forward and get compressed through the brachial plexus. To find your own fore/aft saddle position, I recommend using the Knees Over Spindle (KOPS) method.
First, get on the saddle and place the pedals at the 9 and 3 o’clock positions. Next, drop a plumb line from your front kneecap. It should intersect the pedal spindle (middle of the pedal). This may not put you in a perfect position, but it’s usually a good benchmark.

If the saddle looks good fore/aft, don’t be surprised if you have angle issues. One of the biggest things you have to adjust is seat tilt. If the front of the seat is facing down (even just slightly!), gravity will force you to slide towards your hands, creating pressure that can lead to numbness. Adjust the seat tilt, but know that for most riders, this is just the beginning. Many people can’t tolerate a completely horizontal seat, and it depends on your flexibility, core stability, and your body structure.
While it’s possible to tilt a rider down up to 2 degrees, I don’t recommend tilting the seat up. There are too many negatives to doing so, as it tilts your pelvis posteriorly and places more pressure on it.

2. Overreaching

Handlebar extension can also lead to hand numbness while riding. If you have to overreach your arms to reach the handlebars, your elbows may be at their limit, which can cause your head to tilt forward, which can restrict blood flow to the brachial plexus. If you’re overreaching, a shorter handlebar stem may help you, assuming the seat fore-aft adjustment is set correctly. On the other hand, if the handlebars are too close to your body, you may be putting too much pressure on your upper body to keep your body upright. Don't bend your elbows more than 20 degrees to avoid shortening your reach.
If you need more than 20 degrees of elbow bend and your fore-aft saddle position is already good, you may want to try a longer stem.

3. Handlebar Height

The wrong handlebar height can also cause hand numbness. To achieve a more aerodynamic riding position, many people will want to lower the handlebars. However, if you lack the core strength and flexibility to comfortably maintain this position, you risk putting too much pressure on your hands to support your weight, and this pressure can cause hand numbness. On the other hand, if the handlebars are too high, you may shorten your ride, which can create other problems. In this case, riders often push on the handlebars to keep the bike balanced front to back. From there, this transfers to their shoulder blades, which push the head forward and put more pressure on the hands. To find the right handlebar height for you, first, adjust them so that you can easily operate the brakes with a slight bend in your elbows. With your hands on the handlebars or wrapped around the curved part of the handlebars,
the wrists should be in a comfortable position, neither turned to the thumb side nor the pinky side.

4. Handlebar Angle

Sometimes hand numbness is not caused by too much weight on the hands, but because the wrists are at the wrong angle. The solution?
Adjust the handlebar angle. When using drop bars, it is best to keep your wrist and hand in a neutral grip. In other words, when not using drop bars or gripping the top of the bars, your palm should rest against the outside of the bar head with your thumb bent over the top of the bar head. However, many bikes have flat bar heads, which can cause your wrist to ulnarly deviate, or force your wrist to bend toward your pinky side. This position can cause compression of the ulnar nerve, which can lead to numbness and discomfort in the hand, especially in the ring and pinky fingers. If this is the problem, it can be solved by rotating the handlebars slightly downward, that is, turning the handlebars so that the front of the bar head is slightly turned toward the ground.

Similarly, if the handlebars are rotated upward too much, you will find that your wrist will deviate outward, or bend upward toward your thumb side. In this case, you may feel numbness and discomfort related to radial nerve compression. If this is the case, you will feel pain in your wrist and on the thumb side of the back of your hand. Whatever you do, make one change at a time and ride it for a while to see how it feels before adjusting anything else. While there is a science to bike fitting, finding the best fit for you is often a process of trial and error.