Phillips sees isometrics as a truer measure of strength gains because none of the participants was practiced at it.
The most important disclaimer to make in all of this is to reveal that these participants, while recreationally active, did not engage in regular weight lifting over the last year. They were "untrained" subjects.
"We'll have to do another study with trained subjects or I'll never hear the end of it," Phillips said. However, as people do become trained, even with intense efforts, strength and size results slow down dramatically.
Not everyone's sold
"When you're just starting off, almost everything should work," said William Kraemer, a professor of kinesiology at the University of Connecticut and editor of the Journal of Strength and Conditioning Research. Kraemer says there is a lot of literature to support the model of lighter weights for improving endurance, heavier for gaining size, and heaviest for strength. He also promised new studies coming soon to back this up further.
Kraemer also disagrees with Phillips that it's possible for lighter lifting — even to fatigue — to stimulate all of the muscle. "It's because of the basic size principle. The more weight you lift, the more motor units are recruited. You're also better training connective tissues: bones and ligaments."
I mentioned that most people just aren't willing to work that hard, but Kraemer doesn't like "better than nothing" thinking. He's sees it as "betraying the optimal for the minimal."
Plus, "strength gains are the money-maker with the general population," extols Boston-based Eric Cressey, a sought-after strength coach who trains professional and Olympic athletes.
"Strength is a crucial foundation for power, which is what we lose as we get older." He sees the value in a lighter approach for novice populations, but says lighter loads also can raise potential for over-use injuries. At lighter loads, you must increase repetitions to achieve fatigue, and this can lead to strains. (Phillips counters that heavy loads come with their own dangers of injury, especially for older populations.)
The size plateau
In the end: "Few experienced lifters can make gains for more than a few years without anabolic steroids," says Phillips. "Everybody has a genetic plateau."
"Everything works, nothing works forever," Cressey said. (He's also a competitive power lifter and holds several state, national and world records.)
And though, for now, high-intensity lifting is the default recommendation by most trainers, the heavy versus light argument is far from over.
Kraemer is in favor of starting light to develop comfort, but insists on the need for progression. Regular heavy training is critical for long-term success, he maintains.
Phillips, on the other hand, wants weight lifting more inclusive, so that even the novice and the nervous can get substantial health, strength (and vanity) benefits from it without having to go too far from their comfort zone.
Either way, lifting can do a body good. You win no matter how heavy you go.
Fell is a certified strength and conditioning specialist.