24/06/2026
After 30+ years coaching field sport athletes and 15+ as an S&C Coach, MAS is still a very important number most coaches never test properly, and the one they over-trust once they do.
I did. I put too much stock in MAS.
But for a while it was the best research and idea we had.
Here’s the honest version.
What it is: Maximal Aerobic Speed (MAS) is the slowest running speed at which your body reaches its maximum oxygen uptake (VO₂ max). In simpler terms, it is the exact tipping point where your aerobic energy system is working at 100% capacity; if you run any faster, you must rely on anaerobic energy, which causes rapid fatigue.
One clean number, testable on any pitch with a 6-minute run. Reach 1450metres, your MAS is 1450/360 =4.0278 4.02 m/s or 14.5 kph.
How we used it: prescribe every interval as a % of MAS.
50–60% to recover.
88-100% for aerobic capacity.
110–130% for aerobic power,
For years this was the upgrade — finally, conditioning scaled to the individual instead of the whole squad running the same distance.
Where it leaves you short: %MAS is blind to top speed.
Two athletes on the same MAS, sent out at “120% MAS,” run the identical speed — but for one it’s 27% of their reserve and for the other 19%. Same session on paper. Two completely different sessions in the legs.
The fix: bring in MSS, build the Anaerobic Speed Reserve (ASR = MSS − MAS), and anchor aerobic power , speed endurance and supramaximal work to %ASR — not %MAS alone.
Now the same relative intensity costs the same for every athlete.
That’s the Speed Reserve Ratio system.
Different sports need loading of the various qualities.
Some positions need even more specific.
You get the idea…
MAS isn’t wrong. It’s just half the picture.
Save this for pre-season if you are basketball, rugby or soccer, save it for in-season for Gaelic Games, Aussie rules or soccer in southern hemisphere 🔖
What system are you currently prescribing off? 👇
