Final answer:
A weight that can be lifted for a maximum of eight repetitions is approximately 75% of the individual's one-repetition max. Strength training programs use this estimation for planning and tracking progress. Personal trainers can compare expected to actual weights lifted to adjust training regimes.
Step-by-step explanation:
If a person can perform a maximum of eight repetitions using a certain weight, then that weight is approximately 75% of your one-repetition max. This estimate is based on repetition maximum predictive charts commonly used in strength training and weightlifting. These charts correlate the number of times you can lift a weight to a percentage of your one-rep max, allowing coaches and trainees to estimate one-rep maxes and design training programs accordingly.
For example, if a lifter can perform eight repetitions at 100 lbs, then a one-rep max calculator suggests that the one-rep max (the maximum weight one can lift for a single repetition) would be approximately 133 lbs (100 lbs divided by 0.75).
A personal trainer using this method to assess client performance would compare the actual weights lifted to the expected weights to identify how well the clients are conforming to the planned progression and to make necessary adjustments to training plans.