As has been covered, strength isn’t lost particularly quickly (it certainly hangs around far longer than aerobic capacity). I believe Bondarchuk (the head coach for the entire Soviet athletic development department) wrote that strength hangs around for around 6 weeks. Granted, Bondarchuk’s athletes were very high level, so there’s a good chance they would lose top-end strength faster than an average/intermediate lifter.
That said, there are two key factors involved in the preservation and development of strength:
- The skill of the chosen movement
- The size of the muscles required to execute the movement
For example, one’s strength in the back squat would primarily be a product of:
- Their ability to back squat with correct, efficient technique
- The size of their quadriceps, glutes, adductors, core musculature and perhaps hamstrings
So, to maintain strength to the best of our ability, we need to preserve as much muscle as possible, whilst preserving the skill of the involved movement.
Preserving muscle is relatively easy for most muscle groups, and is more or less entirely dependent on achieving concentric failure in a set of anywhere from about 5 to 30 reps. For stronger muscle groups like the quads, this can be achieved by using a giant set like:
1- Reverse Nordics: 15-20
2- Alternating Pistol Squats to Box: 15-20 ea
3- Alternating Reverse Lunges: 15-20ea
4- 1.5 Rep Bodyweight Squats: 15-20
Filthy, but you would expect to achieve muscular failure by the end.
Importantly, there’s good evidence to show that intentionally slow concentric tempos are not as effective as at stimulating hypertrophy as explosive or controlled tempo, provided that failure is achieved. As such, I don’t recommend using slow concentric tempos like a 5-0-5-0, as this may be less effective than doing more reps at 5-0-1-0.
How about preserving skill? This is the challenge, as skill is load and pattern dependent. Your best best will be to try and perform movements as similar as possible to your key lifts (I’m going to assume: squat, bench, deadlift and overhead press) with whatever load possible, provided that load vector is somewhat similar to that provided by a barbell. For the “skill” movements, I would recommend a grease-the-groove approach where you go for a high total volume, executed as many sets of few reps, with a high frequency. An example here could be something like 8-10 x 10 or even 15 x 5 or whatnot.
Putting that together, a suitable plan could involve a conventional U/L split, where each session has a string focus on achieving muscular failure, without a huge emphasis placed on dynamic correspondence to the big lifts. As a supplement, you could adopt something like 100-250 total broomstick squats and 100-250 total broomstick good mornings daily (a very Westside-esque choice at that) to maintain the skill of lifting as much as possible.
Since the bench press and overhead press are generally well-correllated to overall muscle mass, focusing on maintaining as much upper body muscle as possible will probably be almost good enough to maintain strength on the bench and overhead press