What is training load?
External load is what the player did: hours on court, physical sessions, matches. Internal load is how hard it was for the body. Two players can do the same 90-minute session and carry a very different internal load.
In an academy the simplest reliable measure of internal load is session RPE (sRPE): after a session the player rates the effort from 0 to 10, and the rating is multiplied by the duration in minutes. A 90-minute session at RPE 7 is 630 units.
| Player | Risk | This week | 4-wk avg | ACWR | 8 weeks | Why |
|---|---|---|---|---|---|---|
| Eitan Mor | High | โ | 1160 | 0.11 | Active injuryPain reported | |
| Ido Ben-Haim | High | 2680 | 1625 | 1.65 | Load spikeDiscomfort | |
| Hugo Lambert | Watch | 1400 | 940 | 2.02 | Load spike | |
| Tamar Golan | Watch | 865 | 981 | 0.88 | DiscomfortPoor sleep | |
| Clara Dufresne | Low | 2315 | 1954 | 1.18 | Poor sleep | |
| Noa Friedman | Low | 930 | 703 | 1.32 | Load rising |
The acute:chronic workload ratio (ACWR)
Acute load is what the player did this week. Chronic load is the weekly average over the last four weeks โ what the body is used to. The acute:chronic workload ratio compares the two: around 1.0 means the player is training as usual; well above 1.0 means a sudden jump.
Sports-science research has linked sharp rises in this ratio with a higher risk of injury. The reference zones most coaching teams use โ and the ones Ace It uses โ are:
- Below 0.8 โ under-loaded: often illness, injury or time away
- 0.8 to 1.3 โ the zone most teams aim for
- 1.3 to 1.5 โ rising: keep an eye on recovery
- Above 1.5 โ spike: consider a lighter day and talk to the player
A worked example
To keep the numbers simple, use hours. A player has trained 18 hours a week for the last four weeks. This week has a tournament and extra practice: 27 hours. The chronic average including this week is (18 ร 3 + 27) รท 4 = 20.25 hours, so the ratio is 27 รท 20.25 โ 1.33 โ watch.
If the same week reaches 33 hours, the chronic average is 21.75 and the ratio is about 1.52 โ a spike. Nothing has gone wrong yet, but this is the week to plan a lighter day.
Where load spikes come from in tennis
Spikes rarely come from one session. They come from weeks where several things are added at once:
- Tournament weeks with more than one match a day
- The first weeks back after an injury, illness or holiday
- Private lessons on top of the academy schedule
- A new fitness block in the same week as a tournament
- Busy school weeks with less sleep
The ratio alone is not enough
ACWR is an early-warning flag, not a diagnosis. It needs a few weeks of history before it means anything, and it says nothing about how the player feels today.
That is why it works best next to a short daily check-in โ sleep, pain, mood โ and the player's injury history. A rising ratio together with new pain is a conversation to have today, not next week.
How Ace It does it
Tennis hours come from the academy schedule, and players log RPE in the app after physical sessions. Ace It computes weekly load and the acute:chronic ratio with eight weeks of history, and combines it with pain, sleep and injury history into one flag: high, watch or low risk โ with the reason.
The weekly load and injury risk report shows the whole academy on one page: who is overloaded, who is under-loaded and who needs attention.