I go for a 3 week holiday with absolute no strength training... how much weaker will I become after those three weeks?
Types of Strength
The term Strength is usually though of as Maximum, 1 Repetition Max Strength.
However, Power and Speed also fall under Strength".
The length of time before each of these "Types of Strength" to dissipate; decrease is different.
Maxium Strength ususally take longer to decrease when not training.
Power and Speed dissipate at a faster rate.
I have an article on this but can remember what I filed it under.
With that said, the anedoctal data that has been presented falls inline with what research shows...
What happens when you stop working out
You might notice your performance slip, too:
“Speed, endurance, and strength can decrease by 25 to 30 percent within two to three weeks,” says Weiss.
A decrease in Strength by 25-30 percent is substantial.
The Good News...
you return but it will all come back quickly once you start lifting again.
Starting Back
when I come back, I always start with lighter weights than I could do and just add weight every session.
This is the most effective method; starting light and gradually increasing the loading.
Too many overzealous individul start back with loads that are too heavy. This approach limits long term progress.
This is the foundation of Periodization Training; the foundation of all well written/executed Strength Training Programs.
Before long, I’m back to where I was, and usually can lift more than before the break fairly quickly.
Varing Exercises
This essentially elicits the same training effect changing exercise after a Periodization Training Cycle based on a certain number of weeks with specific exercises.
Exercise changes can be as simple as going from a Wide Grip Bench Press in one Periodization Training Plan to a Narrow Grip Bench Press or Incline Press in the New Periodization Training Plan.
As 5 X 5 notes, start with a light load and progressively increase it.
Changes in exercises are more effective than in loading schemes to improve muscle strength.
Changes in exercises are more effective than in loading schemes to improve muscle strength - PubMed
Essentially, this falls into the same category Varying Exercise in Periodization Training Plans.
ABSTRACT
Our findings suggest: (a) CIVE (Constant Intensity-Varied Exercise) is more efficient to produce strength gains for physically active individuals; (b) as long as the training intensity reaches an alleged threshold, muscle hypertrophy is similar regardless of the training intensity and exercise variation.
Periodization Training and Varying Exercises
These are two of the fundmental method that ensure long term training progress.
