Why Injuries Happen: Understanding Load vs Capacity | Physiotherapy in Glasgow

Bad technique is very rarely the sole cause of your injury. At SPG Physiotherapy Glasgow, one of the most common conversations we have with people dealing with pain is around why their injury happened in the first place. Many assume it must be highly specific: poor technique, posture, or some sort of imbalance. However, in reality, that’s rarely the full picture.

More often than not, injuries occur because of a mismatch between loading and capacity.

Load vs Capacity: The Real Cause of Most Injuries

In simple terms:

• Load is what you place on your body through training, sport, and daily life (how much stuff you do, and how hard it is)

• Capacity is how much your body can currently tolerate and recover from

  
  

Injuries tend to happen when loading far exceeds capacity. This mismatch doesn’t always require extreme training. Sometimes even normal amounts of loading can cause problems if your capacity has dropped.

What Reduces Your Capacity?

Your physical capacity isn’t just determined by strength or fitness and is also heavily influenced by external factors. Common things that reduce capacity include:

• High levels of life or work stress

• Not eating enough calories

• Inadequate protein intake

• Poor or inconsistent sleep

• Poor hydration
  

When capacity is reduced, the margin for error becomes much smaller. Training loads that you previously tolerated with no issue can suddenly result in pain or injury.

This is why people often feel like a niggle has come “out of nowhere.”

When Load Becomes the Problem

Capacity is only one side of the equation. The other is how smart we are with loading.

Problems commonly arise when:

• Total training volume increases too quickly

• Intensity ramps up faster than recovery allows

  
  

Exercise selection includes very high-load movements without a solid base

A good example of this is impact-based exercise. Something as simple as jogging places multiple times your bodyweight through one leg at a time, and research shows injury risk can be significantly higher compared to standard resistance training. This doesn’t mean running is bad. It does mean it needs to be earned and progressed gradually.

Introducing high-impact or high-load exercises before building adequate strength and tolerance is one of the most common mistakes we see in the clinic.

Recovery: The Missing Piece

To cover your basics make sure that you:

• Eat enough calories and protein

• Sleep at least 7, ideally 8 hours per night

• Unwind and participate in stress relieving (non-strenuous) activities

  
  

A simple rule of thumb that works well for many people is:

• Avoid loading the same body parts more often than every second/third day

• Take at least 2 total days of rest per week

This allows time for tissues to recover and adapt. From there, frequency can be adjusted based on individual response, training history, and external stressors.

More isn’t always better, especially when recovery resources are limited.

Recovery is not optional - it’s part of the training process.

If You’ve Picked Up a Niggle, Ask These Questions

If you’re dealing with pain that feels unexpected, it’s worth reflecting on recent changes:

• Has training volume increased sharply?

• Have loads become significantly heavier?

• Have you added high-impact or speed/power based exercises?

• Has recovery, sleep, or nutrition dropped off?

• Has stress or workload increased?

In most cases, the answer lies somewhere in this combination.

How Physiotherapy Fits In

This process of identifying where the load–capacity mismatch occurred is exactly what physiotherapists aim to do during a subjective assessment.

At SPG Glasgow, physiotherapy isn’t just about treating symptoms, it’s about understanding:

• What changed

• Why did the injury happened

• How to restore capacity

• How to reintroduce load safely and progressively

• How to restructure training to reduce re-injury/future injury chance
  

This approach helps reduce recurrence and builds long-term resilience, not just short-term pain relief.

Watch Tristan's Reel on the Topic

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If you’re struggling with pain, a recurring niggle, or an injury that doesn’t quite make sense, it’s rarely random.