Since intuitive exercising does not work, we need some benchmark to measure how well (or badly!) we or our clients are doing.
Use fitness equipment not to get a precise measure of what it pretend to measure (these machines are notoriously bad at it) but to measure the trend over time.
It’s like scales; measuring body weight accurately is much harder than it seems, as this video amusingly demonstrates. Your clothes won’t give you accurate measures either; but it won’t fool you, and will not allow you to fool yourself, about the direction of the trend.