When performance stalls, the instinct is to train harder. Often the answer is in your bloods.
Consistent training puts real demand on iron, vitamin D, muscle repair and hormones. If one of those is running low, no amount of extra volume fixes it.
Ferritin, not just haemoglobin
Endurance athletes can be low on iron stores long before anaemia shows up. Ferritin catches it early — and it's strongly tied to how heavy your legs feel.
Vitamin D affects power and bone
In a UK winter, most athletes are low. It matters for muscle function, immune resilience and stress-fracture risk.
CK and inflammation tell you about recovery
Creatine kinase and inflammatory markers help separate good training stress from a load you're not absorbing.
Hormones show when you're under-fuelled
Low testosterone in men and cycle disruption in women are classic signs of under-recovery and low energy availability, not weakness.
What should you do if these sound familiar?
Test in a steady block of training rather than the day after a race, and retest a few months later so you can see the direction of travel.
Our sport panels are built around endurance, power and concurrent training, for both men and women.