Glossary: Load, IF, Fitness, Fatigue, Form

IF, Intensity Ratio

A ratio: normalised power (or pace) divided by threshold.

• IF 1.0 means you trained at threshold.
• 0.65 is recovery or endurance.
• 0.85 is sweet spot or tempo.
• 0.95+ is race-pace or VO2.

IF makes a 1 hour easy ride and a 1 hour tempo ride directly comparable in difficulty.

Load, Load Score

A score combining how hard and how long a workout was, scaled so that 100 Load equals one hour at threshold (IF 1.0).

• A 2 hour endurance ride at IF 0.7 produces roughly 98 Load.
• A 40 minute FTP test at IF ~0.95 produces roughly 75 Load.

Load lets you compare workouts of different durations and intensities with one number.

rTSS, bTSS, sTSS, hrTSS

Sport-specific Load variants:

• rTSS: running Load, computed from pace and threshold pace.
• bTSS: bike Load (the original, power based).
• sTSS: swim Load, computed from CSS.
• hrTSS: HR-based Load, used when power is not available.

Sport-specific Load lets you see where the load is actually coming from, instead of one undifferentiated number.

Fitness, Fitness (chronic load) (fitness)

A 42 day rolling average of daily Load. Climbs slowly as you train consistently. Higher Fitness means more fitness, but also more accumulated fatigue if you ramp it too fast.

Fatigue, Fatigue (acute load) (fatigue)

A 7 day rolling average of daily Load. Spikes after hard weeks.

Form, Form (Load Balance) (form)

Fitness minus Fatigue.

• Positive Form: you are fresh (good for racing, weak signal for training adaptation).
• Negative Form: you are tired (good for training adaptation, bad for racing).
• Negative 5 to plus 10 is a roughly balanced range.

A note on Load

Load is useful for trends, less useful for comparing one workout to another exactly. A 200 Load hard run beats up your body very differently from a 200 Load easy bike ride. The Hub keeps Load domain-separated so you can see where the load comes from.