Just do them on your knees instead of your toes for a while and you'll find you will be able to get a few more reps over time... after that start to vary your hand position so that all areas of your chest are worked.
You can start by doing wall or elevated push-ups, or do them on your knees first friend. When you get the groove of it, try and rev it up to 75-100 reps in one set. When that gets boring, you're probably ready for the regular push-up. That's how I went about the standard push-up, at least. Hope it works for you.
I'm going to start doing this. I can do about 15-20 with good form? Which is pretty embarrassing when you're doing it as a class.
I find this program pretty useful for those who have trouble doing many consecutive push-ups. http://hundredpushups.com/index.html
Where do you feel your form collapse? I've found most often the weak link in the chain are the deep abdominals and muscles around the lumbar/thoracic spine. Are you doing core-specific, and particularly spinal muscle strengthening exercises (other than isometric exercises, like pushups)?
Looks like a good programme, but I wasn't keen on the form of the pushups shown. I don't like pushing up to a locked straight-arm, it's doing nothing for you and I think of it as cheating. Some bad neck positions shown, and that black belt woman on the first page has her hips raised.
Anyone has ideas on how to do them more explosively? I can do 15-20 with good form, but they're much slower than I'd like, especially towards the end.
getting stronger should help, as should plyometric pushups (first aim to have your hands leave the ground, then maybe work towards clapping pushups (focusing on airtime, not on clapping faster, which is cheating ), then get even stronger
throwing stuff for distance with a similar motion (like a crossfit wall ball toss, or throwing a medicine ball ala a basketball throw, maybe some shot put type unilateral throws as well) may also be of use
You could try my bouncing press ups, where you raise the entire body about 2 inches from the floor. Just increase or decrease the range of motion to suit your needs. [ame="https://www.youtube.com/watch?v=ico8AzGWAMs&list=UUCEvC8J27lX6ns2hNgY3zUQ"]Bouncing Press Ups.wmv - YouTube[/ame]
OP if you can't manage a decent number flat, you can supplement with easier versions like doing against a wall (or other means of elevating hands, to shift more weight onto your feet) or doing them on your knees, which shortens the leaver and lets you shift more weight off your hands.
I used to be a fitness instructor and helped out quite a lot of obese people,I found the best way to help them was to focus on strength at first,so squat,deadlift and bench press 5x5,3 times a week. I don't care if you can only lift 20% of your bodyweight (or even if you can't add any weight for the squat) ,work toward your goals steadily,there are no quick fixes. Also do a couple of days a week light cardio,even just walking/hiking for an hour if you feel that pushes you,eat properly and follow your program stringently. depending on how disciplined you are (remove the ego when trying to gauge this) you may NEED a training partner or personal trainer. good luck.