Light lifting, big muscles?
Study runs contrary to common wisdom and finds that substantial growth can come without all the grunting and bulging associated with heavy weights. The key? Repetitions.
By James Fell, Special to Tribune Newspapers
7:19 PM CDT, July 25, 2012
Attention fans of heavy lifting: Grab your torches and pitchforks! Someone is questioning your long-held beliefs told by preachers of the hard-core gospel and published ad nauseam in magazines with the word "muscle" in the title.
Here goes: Lifting near your maximum weight is not necessary to build muscle mass and gain strength.
"Consistent practice combined with good nutrition and practicing good form and working to fatigue — no matter what the load — is what makes up the majority of results," says Stuart Phillips, a professor of kinesiology at McMaster University in Hamilton, Ontario.
It's that "no matter what the load" part that has people up in bulging, veiny arms. "Load" is how heavy the weight is, and "heavy = huge" has been preached since Schwarzenegger wore short pants.
"At the risk of inviting death threats," Phillips told me, "I think a lot of the variables in a resistance training program — rest, sets, loads and other variables — are largely redundant in their capacity to bring about strength and (bigger muscles)." More important to Phillips is that you, "Get to the weight room, consistently practice, work to fatigue — this is 80 percent of the job."
And Phillips has some science to back up his claims.
Phillips and his team studied 18 college-age men for 10 weeks. Published in April in the Journal of Applied Physiology, the research examined the results on three weight-lifting routines:
Three sets at 30 percent of maximum (with 100 percent being the maximum amount of weight they could lift for one repetition).
One set of 80 percent of maximum.
Three sets of 80 percent of maximum.
The study focused on leg-extension exercises, and participants were allocated to two of the three routines (a different routine for each leg). The findings fly in the face of current recommendations and state that the lighter-weight routine had the same muscle growth results as the three sets of heavy weights routine. It also showed that the number of sets is important, because lifting three sets to fatigue at the lighter load made muscles bigger than did a single set of much heavier weight.
How is this possible? Traditional thinking is that only heavy lifting works the larger, "fast-twitch" muscle fibers that are more responsive to gaining size, and that lighter weights only engage the smaller "slow-twitch" fibers that are for muscular endurance.
But Phillips says traditional thinking isn't on target. His main reason: fatigue. Even with lighter weights, when you do enough reps to tire the muscle — so that no further lifts can be made while maintaining good form — then both fast- and slow-twitch muscle fibers are recruited and muscles grow in size.
Size vs. strength
But though your muscle grows and you do get stronger with the lower-weight routine, your muscles won't be as strong as those of people doing the heavier-lifting routine, the study showed.
Ten weeks into these routines, when strength was measured by seeing how much a test subject could lift for one rep, those lifting light weights to fatigue were 20 percent stronger, but those lifting heavier weights were almost 40 percent stronger. Those doing the single-set routine were about 30 percent stronger.
No small potatoes.
Phillips suggests the difference lies in neural adaptations that enable these greater strength capabilities, perhaps coupled with extra confidence from having practiced with heavier weights.
And the proof was in subsequent isometric testing — where test subjects tested their strength against a fixed resistance, so without any movement. The results were just a few percentage points apart.
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