Debunking the Knee Over Toe Myth

Michael Goulden

Last updated: 

2 Dec 2024

2 min. read

‘Don’t let your knees go past your toes.’

For years, I repeated this mantra to my clients. It seemed logical, was supported by respected organisations, and appeared unchallenged in a recent NSCA journal:

‘[The] knee moving forward of the foot at the bottom of the movement should be avoided as this compromises the knee and makes the exercise problematic.’

Like many trainers, I accepted this guideline without question. Until I didn’t.

From Acceptance to Investigation

During my MSc in Biomechanics, something clicked. Previous research has shown that while restricting knee movement in squats reduced forces at the knee, it increased forces at the hips and lumbar spine. Force doesn’t disappear – it redistributes.

This made me wonder: what happens during a split squat? More specifically, what happens to the trailing leg that everyone seems to forget about?

The Experiment

With access to a biomechanics lab, I decided to test two variations:

1. Traditional split squat: knee behind toes (7.6º ankle dorsiflexion)
2. Full ROM split squat: allowing forward knee travel (39º ankle dorsiflexion)

The results challenged everything I thought I knew.

What the Data Revealed

The data revealed a surprising truth. In the traditional split squat, the trailing leg absorbed over 100 times more torque than the leading leg.

However, in the full ROM split squat, this dramatic difference disappeared – the trailing leg experienced only about 1.5 times more torque than the leading leg, showing a much more balanced force distribution.

As Tom Purvis pointed out in an RTS class: ‘…we are so busy worrying about the leading knee being in front of the foot, that we fail to see that the trailing knee is FAR in front of the foot.’

Beyond Rules to Understanding

This small experiment (yes, it was just N=1) highlighted something crucial: our industry’s tendency to reduce complex biomechanics to simple rules often misses the bigger picture.

The real questions we should be asking are:

• What are we trying to achieve with this exercise?
• Why are we avoiding knee torque if we’re trying to strengthen knee extensors?
• Are we considering force distribution across the entire system?
• How do individual structural differences affect optimal positioning?

Moving Forward

I no longer tell clients to keep their knees behind their toes. Instead, I assess their:

• Unique structure
• Specific goals
• Movement quality
• Force tolerance

The ‘knee over toe’ debate taught me a valuable lesson: our role isn’t to memorise and enforce universal rules. It’s to understand principles deeply enough to make informed, client-specific decisions.

After all, that’s what separates the recipe followers from the exercise chefs.