Why Do My Legs Shake When Doing Leg Extensions?

leg extension
August 17, 2022 0 Comments

Table of Contents


In this article I will be answering the question “why do my legs shake when doing leg extensions?”. Many people experience this issue, it is quite common in fact.

This article will explore various reasons why this phenomenon occurs. By the end you will have lots of knowledge about this topic.

Why Do My Legs Shake When Doing Leg Extensions?

Shakiness in the legs when performing leg extensions is a sign that you are making the muscles work and they are under tension. It can also occur as a result of fatigue, nutrient imbalance or going too heavy.

If you are doing your leg extensions in a tempo training fashion you will notice that the leg shakes will be even more pronounced. 

Action Tremor

Action tremor is the technical term for what is going on when your legs shake during leg extensions. 

The tremor that occurs during movement is known as kinetic tremor. In most cases a kinetic tremor has a frequency between 2 and 7 Hz. 

In the case of the leg extension, the kinetic tremor is exacerbated towards the end of the range of motion. I perform leg extensions every week in my own training and pause each rep. I find that the action tremor is the most pronounced at the end of the range of motion. 

Tempo Training

If you find that your legs are shaking excessively from the leg extension, one possible explanation could be tempo training. If you are performing the leg extension in a tempo fashion you will find that your legs will shake significantly. 

Tempo training is when you count on the way up when performing the exercise. You can also count on the way down. In the case of a leg extension, a three second tempo would be counting 1-2-3 on the way up and the same on the way down.

This is very tough and elicits a lot more muscle growth. When you exercise in this way you will find that you get a lot more kinetic tremors in your legs. The muscles are working very hard and you are putting them under lots of tension. 

In the video below Eddie Hall is having a leg workout with bodybuilder Martin. You will see them doing leg curls and putting lots of tension on the muscles. Like they say, if you don’t see your legs shaking on this exercise you aren’t working hard enough!

There is a good article from Men’s Health going into detail on the leg extension. You can read it here


Legs shaking from leg extensions can also be caused my muscle exhaustion. If for example you perform leg extensions after doing heavy squats you will find that your leg muscles are already exhausted.

You will experience more kinetic tremors in your legs from leg extensions than you would if you performed leg extensions before squatting. 

In addition, if you are doing a high rep set of leg extensions, as you approach muscular failure your legs will start shaking a lot more. Lactic acid will build up in the muscle and you will start screaming.

Many people don’t approach muscular failure on leg extensions as the lactic acid build up can be very painful. It takes a lot of willpower and mental fortitude to really push yourself to the limit on this exercise!

Going Too Heavy

Another big cause of kinetic tremors during leg extensions is going too heavy. A lot of people don’t seem to understand that the leg extension is not a power movement.

The objective should not be to go as heavy as possible on this exercise. The focus should be on working the muscle through a full range of motion and putting it under tension. The leg extension is designed to be used to build up the musculature in the quads. 

When you go too heavy on this exercise, you increase the risk of injury and stresses on the knees. You also will experience a lot more kinetic tremors during the range of motion.

Nutrient Imbalance

Shaking in the legs during leg extensions can also come about from nutrient imbalances, namely salt.

If your sodium levels are too low this can result in the muscles cramping up. This can become more significant as your muscles become fatigued later on in workouts or sets. 

Therefore, it is a good idea to increase your sodium intake before strenuous workouts. A good way to do this is just to down a sachet of salt with some water. 

Final Thoughts

To conclude, in this article I have answered the question “why do my legs shake when doing leg extensions?”. There are a plethora of possible reasons for this which I have explored thoroughly.

It can happen from deliberate tempo training, nutrient imbalance, going too heavy or muscle exhaustion. 

I really want to hammer the point home that you should not be treating the leg extension as a power exercise. Doing this is counterproductive and you can experience far worse effects than merely shakiness in your legs.

Instead, use the leg extension to work the quadriceps muscle and pump blood into the area with light to moderate weights. Focus on the muscle contraction and getting some time under tension to elicit good hypertrophy.

If you have any questions on this topic please leave them in the comments below.

As always, stay safe and enjoy your training!

>> RELATED: Why do people go so heavy on leg presses?


Leave a Reply

Your email address will not be published.