When something unexpected comes up and you're forced to pare down training time, you need two things: efficiency and focus.
Instead of a more conditioning-intensive plan where your anaerobic endurance could be a significant and potentially limiting factor, you can get some good strength work done in bare minimum time with the right programming.
The 5,4,3,2,1,5 Method
This was used by '70s raw powerlifter and record-setter John Kuc. He was the first lifter to squat 900, first to pull 850, first to total 2,300, and he got there with simple programming.
For our short 20-minute session, go through a quick general warm-up first. That's something you can never skimp on, especially when you still want to lift heavy in the session. Three or four minutes is plenty of time to get some blood flowing and hit a mobility drill or two.
Choose one big exercise. Remember, we need efficiency, so any big basic compound exercise will be fine as long as you can safely hit a heavy single. That means rows, chins, dips, and dumbbell work aren't the best ideas.
Do one or two light warm-up sets for the movement, then get started. The key to this countdown-style approach is in the loading. You gradually work up in weight while dropping reps, and then reduce the weight and bump the reps back up for a final set:
- Do a set of 5, rest a minute.
- Do a set of 4, rest a minute.
- Do a set of 3, rest two minutes.
- Do a set of 2, rest two minutes.
- Do a single (which should be very hard but not a true max), rest a minute.
- Finish with a set of 5 using a weight somewhere between what you used for the first set of 5 and the set of 4.
For example, you might go:
That very last set is key. By dropping the weight, you can focus more on picture perfect form even in a relatively fatigued state.
Plus, you're in the sweet spot of post-activation potentiation, which basically means your brain is saying "Pfft! After that heavy work, this one's a feather." So the set should feel easier than the very first because your CNS is amped up and your muscle recruitment is optimized.
If you decide to adopt this plan for the coming weeks, you'd progress by adding 5-10 pounds to every set. Or just return to your regularly scheduled program and keep this in your back pocket until next time.