Activities Sports & Athletics Muscle Back Irons: What They Are, Who Should Play Them Share PINTEREST Email Print The Titleist iron on the left is a muscleback; the one on the right is a cavityback. Acushnet Golf Sports & Athletics Golf Basics History Gear Golf Courses Famous Golfers Golf Tournaments Baseball Basketball Bicycling Billiards Bodybuilding Bowling Boxing Car Racing Cheerleading Cricket Extreme Sports Football Gymnastics Ice Hockey Martial Arts Professional Wrestling Skateboarding Skating Paintball Soccer Swimming & Diving Table Tennis Tennis Track & Field Volleyball Other Activities Learn More By Brent Kelley Brent Kelley is an award-winning sports journalist and golf expert with over 30 years in print and online journalism. our editorial process Brent Kelley Updated April 21, 2018 "Muscle back" (also spelled as one word, "muscleback") is a term that describes the design of some golf irons played mostly by very good, including the very best, golfers. When an iron is a muscle back, or a club is referred to as a "muscle back iron," it means that iron has a full back of the clubhead, as opposed to a hollowed out or scooped out back of the clubhead that is seen in what are called "cavityback irons." That hollowing out of the back of the clubhead in cavitybacks helps create game-improvement qualities known as perimeter weighting and forgiveness. Muscle back irons are also called "blades," or the muscleback part of the clubhead can be referred to as a "full back." Muscle back irons are usually manufactured through a forging process, although they can also be made through a casting process. (See Forged Irons vs. Cast Irons for info about these two manufacturing processes.) Who Should Play Muscle Back Irons? Who can play musclebacks? Anyone who wants to! Who should play muscleback irons? Not many golfers at all. Musclebacks are more exacting irons, they require more precision to play well, compared to cavitybacks. Which is why muscle back irons are usually only played (or at least played well) by lower-handicappers. Any golfer who is not a low-handicapper—single digits, low single digits, even—should stick with cavityback irons. (Even some professional golfers prefer irons with full or partial cavity backs.) Why? Compared to cavityback irons, with muscle back irons there is a greater loss of distance and a worse feel on off-center strikes of the golf ball.Because the musclebacks have full backs on the clubhead, musclebacks tend to have a higher center of gravity location, which can produce a lower trajectory preferred by many highly skilled golfers. Mid- and higher handicappers, however, tend to need help getting the ball higher in the air.A muscle back iron will also have a lower moment of inertia (essentially, less forgiveness) than a cavityback, because of the cavityback's perimeter weighting. Why Do Some Golfers Prefer Musclebacks? That all being the case, why do some golfers prefer muscle back irons? Well, a good enough golfer can consistently repeat his or her swing and place the clubhead onto the ball properly over and over again. A golfer who doesn't require the help provided by game-improvement clubs may prefer certain characteristics of the muscleback iron. Musclebacks provide greater feedback to a golfer, for good shots and poor ones. Many golfers, even those who don't play musclebacks, believe they are a more attractive design: they just look cool. They have a more muscular (no coincidence) feel to them when struck well. Plus, once upon a time basically all irons were musclebacks. It was really the only iron head design manufacturers knew. Then Karsten Solheim (the founder of Ping) came along and popularized the concept of "perimeter weighting" by scooping out the back of the iron head. This had numerous beneficial effects for golfers (higher MOI and therefore more forgiveness, chief among them), but such irons, in their early days, were immediately tagged as irons for bad golfers. Musclebacks then had cachet, in other words: If you were a good golfer, you played musclebacks. Cavitybacks, by the way, are not "irons for bad golfers," they are irons for most golfers. But that "cool" factor of musclebacks has never really worn off, at least for many golfers who love traditional things. There's sometimes an aspirational element to musclebacks: Some golfers buy them as incentive to becoming better. "I'll work on my game until I'm good enough to play these irons." One Myth About Muscle Back Irons There is also a reason cited by some who prefer musclebacks that, it turns out, is a myth. Many golfers believe that muscle back irons make it easier to "work the ball," that is, impart the desired spin and flight characteristics through the swing. Turns out, though, that is not true. Golf club design veteran Tom Wishon of Tom Wishon Golf Technology suggests anyone stuck believing that myth "just ... look at the pros on the PGA Tour. And more than half pros who play for a living use cavityback irons." Wishon continues: "Because of course design or wind conditions, all pros have to be able to intentionally 'work' the ball to be able to compete. If it really were true that a cavity back could not 'work' the ball, you would see all the pros using muscleback irons. Since that is not the case, this statement stands as a myth." The Bottom Line on Musclebacks Muscle back irons are very pretty golf clubs, and very good golfers might like certain things about them enough to prefer them over cavityback irons. But the vast majority of golfers should stick with cavityback irons.