Here is a good question about performing at a maximum level on fitness testing. As with weight training, you do not want to do daily high repetition calisthenics on the same muscle groups. In fact, when you push the limits of 500‑1000 reps in a workout, you could still be pushing it too much still. See what young hard charger says:
Stew, I used to do 1000 pushups a day and built up to 80 pushups in two minutes. After reading your article on Stop Doing Daily PT I dropped to 1000 pushups every OTHER day. I am doing well with everything else (pullups, situps, run, and swim) but cannot get over 100 pushups on the PST? What gives?
Your problem is pretty common actually. Even though your volume of pushups is very high, you would think that 100 reps in a two minute period is going to happen sooner than you think. Well, this increase is tough. It is like dropping from a 7 minute mile pace to a 6 minute mile pace. It takes time AND practice with two minute pushups tests. Also in the Navy SEAL / SWCC, EOD Physical Screening Test (PST) you have to swim 500 yards first, so when you do your pushup sets you should mix it with swimming. For instance do Swim / PT like this:
Repeat 5– 10 times
swim 200 yards
pushups max reps on the first 2–3 sets, then drop to 50% of your max and see if you can finish 5–10 sets
Abs of choice — rest with 50 abs or a 1 minute plank pose
This will get you used to swimming first and then trying to do your PT tests. If you can, add a pullup bar on the pool deck (power tower, etc) and mix in pullups too.
But the biggest issue is likely your lack of properly recovering. So you may want to drop your pushup reps even further — maybe even to 250–300 reps in a workout period, but doing them in sets of 80+. Eating right, hydrating, rest in between workouts, and most important a good night’s sleep is key to your increased performance on this test.
When you fail at pushups, keep going with knee pushups even if it takes you over two minutes to finish the set. So don’t stop at two minutes. Push your endurance / muscle stamina to ace the test better. There is some debate out there on whether or not to fail. I would agree that you do not want to fail EVERY set, but failing a few sets in your three day a week pushup workout will help you build that muscle endurance you need to get triple digits on a fitness test.
Make sure your form is perfect too: Your hands should be just wider than your shoulders, placed directly at your chest level. Imagine your palms had a bar in them (like in a bench press), when you go down, your hands should be even with your sternum, not any lower or higher. When you lower a bar to your chest during a bench press, the bar crosses your chest. Do the same with the pushup for the up and down positions.