There are times in your life when you won't want to or can't train long and hard. Maybe it's a job change, a move, or a pandemic event shutdown. Whatever the reason may be, there is plenty to be said for continuing and connecting your super-fitness with maintenance training. Another nice term for this is bridge training. You're essentially building a bridge from your recent landmass of super fitness training to the next one. :)
These workouts don't require much in the way of time and can carry you through several weeks of life-is-a-priority-right-now.
Running
Certainly the easiest to accomplish though the hardest on your body in terms of stress.
#1: 30-40 minutes easy-steady: basic aerobic fitness
#2: 10 minute easy-10 minute moderate - 10 minute mod hard- 5minute easy: aerobic fitness + muscular endurance
#3: 10 minute easy - 8 to 10 x 1 minute threshold to 5k pace / 1 minute easy - 5-10 minutes easy: anaerobic / threshold training
#4: 10-20 minutes easy, then 10-15 minutes of form drills, 5-10 minute easy: technique training
Biking
More time if you have to dress up to hit the road, but not bad if you leave a trainer set up in the house.
#1: 30-40 minute easy-steady: basic aerobic fitness
#2: 10-15 minute easy - 4 x 2 or 3 minute Z3-4 (sub threshold) / 1-2 minute easy between - 5 minute easy: sub-threshold training
#3: 10-15 minute easy - 8 to 12 x 30 second Z5-a/b (over threshold) / 30 second to 1 minute easy - 5 minute easy: anaerobic training
#4: 10 minute easy - 20 minute build to Z4 (90-100% of FTP) - 5 minute easy: threshold training
Swimming
Definitely time consuming if you have to drive quite a bit to get to a pool. If you can hit 1x swim per week during busy life times, that will help you not feel awful when you do return to a regular training program.
#1: 1200-1500 easy continuous: basic aerobic fitness
#2: 400 easy, 100 kick. 9 x 100 descend 1-3, 4-6, 7-9 on :15 (seconds rest). 100 easy: can work every system depending how hard you go on the hard ones.
#3: 300 easy, 6 x 50 technique drills on :15. 12 x 50 as odds fast (up to sprint) / evens easy on :20-30. 100 easy: technique & anaerobic fitness
#4: 300 easy, 100 kick. 5 or 6 x 200 negative split on :30. 50-100 easy: muscular endurance training.
Strength
It is super easy to do bodyweight training with no equipment, or use kettlebells, dumbells, or TRX trainers to have more resistance. You have no excuse not to do something like this at least 2 x per week.
#1: 10-20 pushups - 10-20 squats - ~1 minute prone leg hold. repeat a few times and you've worked most of your body.
#2: 10 burpies - 10 side leg raises each side - 1 minute plank (variations galore). repeat...
#3: 10-20 bicep curls (use a milk gallon if you don't have hand weights) - 10 tricep extensions or overhead press - 20 crunches. repeat...
And bingo. Instead of losing all your fitness, you actually retain most of it and it is 100x easier to get back into a tougher training with a goal routine.
Combine with a sensible diet, you'll find you haven't changed shape either.
Now get moving! :)
Marty Gaal, CSCS, is a USA Triathlon coach who lives in the Triangle area of North Carolina. Marty has been coaching endurance athletes since 2002. You can read more about OSB coaching services at www.osbmultisport.com.