Downsides to working out for 6.5 hours non stop in the gym?

Question

Suppose one trains like this:

Midday Workout Sunday, 21 May 2023 at 13:52

Boxing Class Set 1: 45:00

S&C Class Set 1: 45:00

Random Crazy Dumbbell Medley Set 1: 0 kg × 58

Incline Bench Press (Dumbbell) Set 1: 32 kg × 8 Set 2: 32 kg × 8 Set 3: 36 kg × 8

Bench Press (Barbell) Set 1: 60 kg × 8 Set 2: 70 kg × 5

Squat (Barbell) Set 1: 60 kg × 3 Set 2: 65 kg × 3 Set 3: 67.5 kg × 3

Back Extension Set 1: +10 kg × 8

Bench Press (Barbell) Set 1: 75 kg × 3

Standing Calf Raise (Barbell) Set 1: 25 kg × 3 Set 2: 35 kg × 8 Set 3: 40 kg × 8

Standing Calf Raise (Bodyweight) Set 1: 8 reps

Squat (Barbell) Set 1: 70 kg × 3

Bench Press (Barbell) Set 1: 77.5 kg × 3 @ 10 Set 2: 80 kg × 1 @ 10 Set 3: 80 kg × 1 @ 10

Seated Row (Cable) Set 1: 20 kg × 10 Set 2: 30 kg × 12 Set 3: 35 kg × 12 Set 4: 40 kg × 12 Set 5: 45 kg × 12

Shoulder Press (Machine) Set 1: 15 kg × 10

Pull Up Set 1: 6 reps

Sauna Set 1: 16:00 Set 2: 20:00

Ice Shower Set 1: 3:00

Deadlift (Barbell) Set 1: 85 kg × 8 Set 2: 95 kg × 3 Set 3: 95 kg × 3 Set 4: 105 kg × 2 Set 5: 105 kg × 2

Pull Up Set 1: 5 reps

Bench Press (Barbell) Set 1: 80 kg × 1 @ 10 Set 2: 80 kg × 1 @ 9.5 Set 3: 80 kg × 1 @ 10

Squat (Barbell) Set 1: 70 kg × 3 Set 2: 72.5 kg × 3

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What negative effects if any might there be of training to this level of extensiveness and intensity?

Answer 1

The muscle is a neuromuscular unit. Working out completely exhausted typically does not end up being that effective anymore because the precision and ability in recruiting motor units as well as the inter- and intramuscular coordination breaks down.

Because of this, your max output will be lower than usual, the risk of injuries is heightened and you will probably need a lot more rest time between sessions than the usual few days because of more microinjuries. You might get away with it at a very young age but it's not a smart way to train.

That being said, if you write something like that, please use percentage of one rep max. Absolute values are completely useless.

Any good S&C coach could and should have told you these things.