Indoor gymnasiums are unlocked after receiving a phone call from Sweet after the mission Drive-Thru, introducing the player to gymnasiums. All gyms are open all day, every day. If, in a single day, the player loses 40% fat or gains 20% Stamina or Muscle, the player will have to wait 12 hours before being allowed to workout again.
According to the game's in-game map, there are three major gyms located in San Andreas, each located in the state's three cities and are easily located on the map by red dumbbell icons in the legend. They include:
- The Ganton Gym in Ganton, Los Santos;
- The Cobra Marital Arts Gym in Garcia, San Fierro; and
- The Below the Belt Gym in Redsands East, Las Venturas.
In addition, two more gyms, unmarked, are present in the game, including:
- An unnamed outdoor gym at Verona Beach, Los Santos, emulating the real-life Muscle Beach; and
- A private gym inside Madd Dogg's Crib in Mulholland, Los Santos, unlocked after "A Home in the Hills".
Each gym is equipped with four pieces of exercise equipment:
|Treadmill||Walking/Running on the Treadmill||This exercise increases Stamina and sheds Fat. The treadmill offers 10 speed levels (the higher the level, the faster your stats will change). Higher levels are easier with greater stamina. When CJ begins running, power and distance gauges, as well as a level indicator, appear on-screen. You must keep pace with the treadmill to keep the power gauge full - if it empties, you fall off.|
|Stationary bike||Stationary Cycling||This exercise increases Stamina and sheds Fat.
The stationary Bike offers 10 speed levels (the higher the level, the faster your stats will change). Higher levels are easier with greater stamina. When CJ begins cycling, power and distance gauges, as well as a level indicator, appear on-screen. You must keep cycling to keep the power gauge full - if it empties, you'll have to start over.
|Bench press||Barbell Bench Press - Medium Grip||This exercise increases Muscle and sheds Fat.The weights range from 40 lbs (20 kg) to 320 lbs (145 kg). When you begin, a power gauge and a reps indicator appear on-screen. You must get the power gauge to fill to complete one rep.|
|Dumbbells||Dumbbell Bicep Curl||This exercise increases Muscle and sheds Fat.
The weights range from 20 lbs (10 kg) to 110 lbs (50 kg). When you begin, a power gauge and a reps indicator appear on-screen. You must get the power gauge to fill to complete one rep.
Sparring and fighting styles
Each gym has a trainer with a different fighting style, but the player will only have access to them when the player has amassed enough muscles. At each, walk into the marker and reply positively when the trainer asks if you want to learn some new moves. The training takes a tutorial-type approach, with tips on-screen to tell you how to execute the moves and when. You must defeat the trainer to learn the new moves. Each teaches you a new Running Attack, Ground Attack, and Combo Attack.
- The Ganton Gym features a Boxing trainer.
- The Cobra Marital Arts Gym features a Kung Fu trainer.
- The Below the Belt Gym features a Muay Thai trainer.
If the player forfeits a sparring match at any gym, they will lose all weapons they are carrying and will be unable to recover them. This is more likely to happen at the Cobra Marital Arts Gym, where the player simply has to step off the floor mat to end the match.
There is a glitch that prevents you from using any equipment, where the game notifies you that you have trained enough, even if you haven't exercised at all after a lengthy period of time. It may be caused by any of the following:
Madd Dogg's Mansion
The glitch occurs most commonly by saving at Madd Dogg's mansion. It is unknown what exactly triggers this glitch, but it can be attributed to the existence of gym equipment in the mansion, making the game treat it as a gym.
The glitch has also been found to happen if you save your game in two different slots, in a very short time. For example: Slot one save time is 16:13, and slot number five is 16:18, then nine times out of ten, the glitch will occur.
New Year's Eve Glitch
It has been recently discovered that the glitch can also occur if CJ reaches his limit on December 31 (ingame time; the game actually tracks days and months of the year, but this is never used in actual gameplay). In this case, CJ will be unable to work out indefinitely.
The reason this occurs is because when CJ reaches his limit on a particular day, he is not allowed to work out until the next day. Since the game does not track years, there is no such day that exists after December 31, as the game's internal calendar rolls back to January 1 after December 31.
Theoretically, the probability of this glitch occurring when CJ reaches his limit is 0.3%.
- If viewed close-up using the zoom features of the camera or sniper rifle scope, players can see the logo of the Cherry Popper Ice Cream Company on the side of any gym's dumbbells. Indeed, both the weights at the bench and the dumbbells derive their textures from those intended for wooden boxes. This is actually a glitch which was fixed in 10th anniversary edition.
- The player also has a fighting style before the player unlocked any of the styles in the gym. This style does a continuous punch and kick combo and there is no official name for it. The running and ground attack are the same as the default punching. After unlocking a fighting style in the gym, the player cannot retrieve it without the use of mods. The only way of keeping it is not learning any other style througout the game. The attack is surprisingly strong, the kick is guaranteed to make the opponent fall on the floor and destroy a lampost or fence.