adjective or comparative adjective for measurements and rates

Question

I was going some through articles about fitness and I encountered these two sentences.

1. Lifting lighter weights often means you're able to perform more repetitions for each exercise you complete
2. Lifting light weights won't build muscle mass no matter how much you pump

So I was wondering what is the difference between using light and lighter. Because if I use light for the first sentence and lighter for the second sentence, both sentences will still make sense.

What about these sentences?

• Running at a higher/high speed is better than running at a lower/low speed.
• Running for a longer/long distance is better than running for a shorter/short distance.

Personally I would use higher and lower because it sounds better. But I don't know if there are any rules that I should follow.

Answer 1

Context is all. "I drink lighter beer than I used to but I really don't like "light beer." The first "lighter" means lighter than before, the second is more attributive than comparative -- in fact, in the USA, brewers have sanction to spell it "Lite" and codify it as a discrete entity in terms of water content (higher) and calorie content (usually lower). If the cited sentences about weightlifting are meant for a general readership of all weightlifters, a more precise wording might be a good idea -- just to specify whether "lighter weights" means "the lighter end of standard weights that you have been lifting," as opposed to "light weights," a separate class of weights that are lighter than standard weights.

Answer 2

The comparitive versionas are more inclusive.

Think about running for a moderate distance. Or using moderate weights, or running at moderate speeds. The comparative version can tell you moderate is better than short/light/low, while the non-comparative ignores these completely, unless you make an inference that 'long' and 'short' etc. are really comparative; and if that is the case, the comparative version is the clearer.