Sounds like you could use some extra muscle
You definately don't need any more muscle for those events. Instead, you need to build up your muscle endurance. Muscle building will have an adverse effect on your decathalon events. Having done four years in the Marine Corps grunts myself, we did nothing but endurance running. The only way you'll get more proficient in something is to do it as frequently as possible. Here's a few things we (my platoon) did for increased performance:
1. Have a workout partiner and practice fireman carrying him for a good distance uphill. Get to the top and drop down to do however many pushups.
2. Simply jump-roping for 3 minutes, one minute rest, then hit it again.
3. When jogging long distances by yourself, try interchanging speeds. For example, if you are running along side a road, pick 4-5 light poles (or trees) down and sprint all out. After you reach it, then bring the speed back down long enough to catch your breathe. Along the way, maybe each half mile, drop down and either do mountain climbers or pushups.
This is what you should be focusing on when preparing for any Marine Corps event. When practicing, it's important to wear the full gear list. You'll short change yourself if you wear shorts and a pair of sneakers. For the situps, it's probably elbows touching the knees. This is what our PFT consists of.
-The run in the woods won't be fast. However, before you begin, tie your shoes as tightly as possible for two reasons.
1. So you won't twist an ankle.
2. So you won't have to stop running to tie them and fall behind.
- The hardest thing you'll do is the stretcher carry. The best advice I can give on that is to continue rotating out with the odd man (if there is one). This isn't something you can train for, just another endurance event.
The only supplements that helped me through the Marine Corps was:
- BCAA's (I suggest Xtend) It'll maintain what muscle you have as well as give them fuel to burn.
- ABB Carb-Force: Something that has a lot of liquid carbs. Again, this will help give you the energy to go the distance. Any drink with an adequate amount of carbs/dextrose.
-Gatorade for obvious reasons.
Any Q's, shoot me a pm.