Blood Sugar and Performance

The graph presents a simple, highly reductive visual model of how perceived performance might change as blood glucose levels drop.

The main message is that glucose concentration cannot be categorized simply as "normal" or "low," but can also be associated with a gradually deteriorating cognitive and physical state.

Scientific approach

Physiologically, glucose is a primary energy source for the brain, so a drop in blood sugar can indeed cause attention deficits, impaired reaction times, irritability, tremors, or weakness.

However, the graph displays this relationship in an overly direct, linear manner, because in reality, symptoms depend heavily on individual adaptation, the rate of the blood sugar drop, insulin levels, prior nutritional status, and whether the individual is accustomed to chronically lower or higher glucose values.

The "performance" scale in the image is illustrative rather than a clinically validated measurement tool.

Values around 100 mg/dL can be perfectly adequate for many healthy individuals.

Performance degradation becomes significantly more marked when glucose drops into the lower end of the physiological range, especially if this happens rapidly.

Blood sugar is not an insignificant variable, and its decline can have a noticeable effect on well-being and cognitive function.

 

Performance and blood glucose values

• 140 mg/dL: Performance is at its maximum, at 100%.
• 125 mg/dL: According to the graph, performance begins to decline but remains at a high level.
• 100 mg/dL: Performance drops to approx. 85%. According to the label: "You might feel like you're at 100%, but you aren't optimized."
• 75 mg/dL: Performance starts to plummet, reaching 75%. "You're about to bonk, but you have no idea yet."
• 60 mg/dL: Performance drops to 50%. "You might feel fine, but your focus is already impaired."
• 40 mg/dL: Performance drops to a critically low level, just 5%. Severe hypoglycemic range.

 

What is "bonking"?

A term used in endurance sports for sudden, severe exhaustion.

It is caused by the complete depletion of glycogen stores and a drop in blood sugar levels.

 

Summary

Overall, the graph draws attention to the fact that falling blood glucose levels can lead to a decline in mental and physical performance, but the correlation is not this simple and is not identical for everyone.

The image is illustrative, but it should be treated with caution because the actual physiological response is more complex than this.

 

 

Sport and blood glucose: CGM-based training optimization