From Sim Dynasty Rulebook

Why was this necessary? Because fatigue impacted the game far more than it should.

First, let's define our terms. You will see both

In game design, everything is about balance and in game play everything is about making decisions. If the balance is off enough that a blanket piece of advice like "Set all players on Conditioning drills, and set the Substitution settings as high as possible" is true, then important decisions are being taken out of the game, leaving less differentiation between team owners. To look at it another way, the two things that decide a game are owner decisions and random chance; for each decision opportunity lost, random chance plays a bigger part in the outcome.

With that in mind, several changes were made some time ago to how fatigue is handled during a game; however, advice is still given based on the old system. Here are the details of how fatigue is handled:

In the past, fatigue was straightforward: For every 5 points of fatigue, a player lost 2% from his ratings, so at the default replacement point of 50%, a player was playing at 80% of his maximum skill.

Under this system, even small amounts of fatigue took the skill edge off of star players, so keeping energy at its highest level was paramount. Thus, the advice to substitute at 80% came into fashion, as the backup player at 90 or 95% energy was likely to perform better than the starter at 80% energy.

The falloff does get steeper, though. Here are some examples:

At 95% energy, a player has 99.8% of his skill.

At 90% energy, a player has 99.0% of his skill.

At 85% energy, a player has 97.8% of his skill.

At 80% energy, a player has 95.2% of his skill.

At 75% energy, a player has 92.4% of his skill.

At 70% energy, a player has 89.0% of his skill. (About equal to the old 80% energy level)

At 65% energy, a player has 85.2% of his skill.

At 60% energy, a player has 81.1% of his skill.

At 55% energy, a player has 76.7% of his skill.

At 50% energy, a player has 72.2% of his skill.

Another important change related to fatigue is that in the old system, players started to recover energy the moment they left a formation. This allowed you to substitute two players back and forth and essentially neither would ever tire because they recovered so quickly. Now, a player has to be off the field for 30-90 seconds (depending on Stamina) before they start to recover energy. (These are "time-of-day" seconds rather than game clock seconds, so in practice this means most players will start recovering after 1 or 2 plays off the field.) Thus, swapping two players or two sets of players back and forth will have a more negative impact as no one really gets time to rest properly, unless they have a high Stamina.

How does this relate to Conditioning? Conditioning represents the maximum Energy level a player can have during a game. In the past there was enough difference between 95% and 100% that some owners would put their whole team on Conditioning drills. Now, that strategy will be less necessary. A player at 100% Conditioning can of course play at his maximum longer, and players with Attitude problems may still need Conditioning on their bad weeks, but it will now be far more productive to make Conditioning decisions on a case by case basis rather than just blanketing everyone in Conditioning and giving up the potential development from other drills.