Understanding Total Force Imbalance
By Jaimie Fuller
Most swimmers think their stroke is balanced.
The data says otherwise.
One of the most common issues we see in eo SwimBETTER data is Total Force Imbalance – where one arm consistently produces more force than the other.
Most swimmers can't feel it.
Most coaches can't reliably see it from pool deck observation or video alone.
But over distance, the consequences compound:
- wasted energy
- disrupted rhythm
- reduced efficiency
- increased injury risk
That's why Total Force Imbalance sits at the top of our Technical Error Index. It's the most common measurable asymmetry we see in freestyle swimmers of all levels – and one of the most revealing.
What is Total Force Imbalance?
Total Force Imbalance – also known as bilateral asymmetry – occurs when one side of the stroke consistently produces more force than the other.
Not just occasionally.
Not just when fatigued.
Repeatedly across the session.
In eo SwimBETTER, this appears clearly in the Stroke Rate & Force (or Stroke Rate & Force) chart. Left and right bars are displayed side by side for every stroke. When one side repeatedly produces more output, the asymmetry becomes immediately obvious.
Unlike video, eo SwimBETTER measures the actual output of each hand independently – stroke by stroke. Swimmers and coaches can see:
- which side is producing more force
- whether that force is actually propulsive
- how symmetry changes under fatigue
- whether interventions are improving balance over time
Sometimes the imbalance only appears under pressure or fatigue. Other times it persists throughout the entire session.
Either way, it's telling you something important.
Why does it happen?
There's no single cause. Total Force Imbalance usually reflects one of three underlying issues:
1. Breathing bias
The most common culprit. Most swimmers have a preferred breathing side. But breathing doesn't just affect head position – it changes rotation, shoulder alignment, timing, and catch mechanics on every stroke.
Over time, this creates asymmetry in the stroke cycle. Even bilateral breathers often have a dominant side, a more stable catch, or better timing on one arm. The result: one hand simply applies force more effectively than the other.
2. Strength imbalance
Sometimes the difference is physical. One shoulder, arm, or side of the core may genuinely produce more force due to natural dominance, previous injury, or historical training patterns. This is less common than many coaches assume – but when it exists, the data reveals it clearly.
3. Timing discrepancy
In some swimmers, both arms generate similar raw force, but the timing of when they apply it differs. One hand may accelerate earlier; the other may finish later. Even subtle timing differences create measurable imbalance – which is why averages alone rarely tell the full story.
An important distinction most swimmers miss
This is where many swimmers and coaches get it wrong. They see a Total Force Imbalance and immediately conclude: "the weaker arm needs to pull harder."
But Total Force Imbalance does not automatically mean a strength problem.
A swimmer may produce more total force on one side while actually directing that force far less effectively. One hand might be pushing downward, pushing sideways, or losing connection during the catch. Meanwhile, the opposite side may generate slightly less total force – but apply it in a far more propulsive direction.
A swimmer can produce more total force on one side – while actually generating less forward propulsion.
If you intervene based solely on total force, you may solve the wrong problem entirely – or make it worse by adding effort where the real issue is force direction.
Always check the Propulsive % before assuming there's a strength issue. The eo SwimBETTER Force Field chart shows exactly where the force is going. If the "weaker" side has a higher propulsive percentage, the priority is direction and efficiency – not strength output.
Why it matters – especially over distance
A difference of less than 10% between sides is often within natural variation and usually isn't worth intervening on. But when the gap becomes significant – and especially when it persists across laps and sets – the consequences accumulate.
Increased metabolic cost
When one side carries more load, the body compensates. The body recruits additional muscles to stabilise and maintain speed. You burn more energy to hold the same pace.
Disrupted rhythm
Swimming is cyclical. When one side of the stroke behaves differently to the other, rhythm suffers – kick timing changes, rotation becomes inconsistent, and breathing mechanics break down. Small disruptions compound over distance.
Reduced repeatability
Elite swimming relies on reproducing an efficient stroke under pressure. Asymmetry makes repeatability harder to achieve and harder to train.
Increased injury risk
Persistent asymmetrical loading patterns significantly increase injury risk across months and years of training. Swimmer's shoulder, rotator cuff impingement, neck pain, and rotational overload are all more common in swimmers with consistent imbalances.
The body adapts to asymmetry but not always in the way you'd want. And critically: the data often reveals this pattern long before the swimmer reports any pain.
What to do about it
Before changing anything, diagnose the cause. Treating the symptom without understanding the reason behind it usually creates more problems than it solves.
Use a snorkel
If the imbalance reduces significantly when swimming with a snorkel, the issue is almost certainly breathing-related. That gives you a clear starting point: improve breathing mechanics first, before addressing strength or force production.
Check the Force Field
Look beyond total force numbers. Does the "stronger" side have a lower propulsive percentage? If so, the issue is force direction – not output. That requires a completely different intervention.
Correct the cause – not the symptom
Telling a swimmer to "pull harder on the left" rarely helps if the real issue is disrupted catch timing due to breathing mechanics. Focus on timing, positioning, connection, and direction of force – not simply effort.
Slow it down
Stroke mechanics are rebuilt more effectively at controlled speeds. Give the swimmer enough control to feel and reinforce the correction. Once consistency improves at lower tempo, gradually increase stroke rate and confirm the change holds under pressure.
Confirm it with data
After any intervention, compare sessions. Review asymmetry trends. Track whether the gap between sides is narrowing over time. Without objective measurement, improvement is often just guesswork, and guesswork is slow.
The bigger picture
Total Force Imbalance sits first in our Technical Error Index because it's both the most common and one of the most instructive errors we see in swimming data. It acts as a gateway error – often revealing deeper issues underneath: breathing mechanics, timing breakdown, force direction inefficiencies, or fatigue-related compensation patterns.
Bilateral symmetry isn't just about how a stroke looks or feels.
It's a performance marker. A health indicator. A coaching signal.
When one side is consistently doing more work than the other, the body is compensating for something. Finding that something – and fixing it – is where meaningful, lasting improvement begins.
eo SwimBETTER exists to help swimmers and coaches make that diagnosis with confidence. Not guesswork. Not assumptions based on pool deck observation. But measurable, stroke-by-stroke force data that reveals exactly what's happening beneath the surface.
Understand the hidden errors reducing speed and efficiency
Total Force Imbalance is just one of 12 measurable freestyle errors identified through eo SwimBETTER data.
Download the full Technical Error Index to learn:
- the hidden technique patterns slowing swimmers down
- why they happen
- how to identify them in the data
- and what the evidence says about fixing them
Related topics:
swimming power imbalance; swimming force imbalance; freestyle stroke asymmetry; swim technique analysis; swimming biomechanics; propulsive force swimming; stroke analysis; swimming force measurement; swimming injury prevention; eo SwimBETTER; bilateral asymmetry swimming; why one arm is weaker in swimming; uneven freestyle stroke ; one arm stronger swimming; swimming asymmetry correction; freestyle imbalance fix; freestyle stroke imbalance; swimming stroke imbalance; how to fix stroke imbalance in swimming
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