Measuring your strength is important because ..
Your strength, NOT muscle mass is a major determinant of your metabolic health.
Low strength may be an indicator of reduce skeletal muscle health linked to Dynapenia and Sarcopenia. Resistance training alongside sufficient protein intake is THE ONLY way to reverse these to restore your metabolic health.
Sarcopenia and Dynapenia are major causes of raised visceral adipose tissue (VAT or 'middle age spread'). In cardiometabolic health terms, measuring strength is more important than measuring muscle mass. Body composition scales can be useful to show trends, but cannot assess strength. The best ways to assess progress are:
1. the subjective method
What weights can you manage to lift on oustretched arms held for 1 min? This number will creep up as you train and make progress.
Once you find it easy to lift 3 Kg in a 10 min full body workout then you will want to either repeat it ('reps') , or, if short on time, increase the load by moving up to 4, 5, 7 10 Kg (men) and 2-5 Kg most women to get the full benefits.
The weight you work with, is an indicator of your strength.
If you want an objective method, read on.