n the summer of 1974,
Tommy John of the Los Ange-
les Dodgers was one of the fin-
est pitchers in baseball. The
31-year-old lefty specialized in
the sinker, a pitch designed to
induce ground balls that could
be scooped up by the defensively adroit L.A. infield.
Midway through the ’74 campaign, John appeared to
be headed for the best season of his 12-year career,
with a stellar 13–3 record and major-league- leading
.813 winning percentage. Then disaster struck:
in baseball parlance, John’s arm went “dead”; at-
tempting to throw brought excruciating pain. As it
turned out, the stress of having delivered thousands
of pitches since his boyhood in Terre Haute, Ind., had
permanently damaged the ulnar collateral ligament of
John’s elbow. It was the same injury that in 1966 had
forced Dodgers great Sandy Koufax, the era’s most
dominant pitcher, to retire at the height of his powers.
John, however, had one long-shot option Koufax
was denied: a revolutionary new operation, per-
formed by noted orthopedic surgeon Frank Jobe,
in which the damaged ligament was removed and
replaced by a tendon taken from his right (non-
pitching) forearm. Surgery notwithstanding, many
assumed John would never pitch again. But after a
year’s layoff he came back to stay... and stay. John
pitched another 14 seasons, until age 46, and en-
joyed some of his best years, logging 164 of his life-
time 288 victories. More than four decades later,
the career-saving procedure—known ever since as
“Tommy John surgery”—is fairly routine; one quar-
ter of major-league pitchers have undergone the op-
eration, which has an 80% success rate.
If the surgery is commonplace, so is the precip-
itating injury. Damage to the ulnar collateral liga-
ment is a classic consequence of excessive physical
stress—more specifically, repetitive stress, caused
by performing the same action over and over again.
Repetitive motion is the culprit in 50% of all athletic
injuries, be it from throwing, running, jumping or
swinging a club or racquet. But it’s also a hazard of
everyday tasks, such as scrubbing floors or manip-
ulating a computer mouse or smartphone for hours
on end. Whatever the activity, this kind of overuse
throws off the complex anatomical choreography
that allows for human motion. “Your body is made
up of muscles, tendons, ligaments and bones,” ex-
plains biomechanics expert Glenn Fleisig of the Uni-
versity of Alabama at Birmingham, research director
of the school’s American Sports Medicine Institute.
“When someone moves, whether they’re running,
throwing or swimming, the brain tells the muscles
what to do. The muscles move; the bones and the
ligaments and tendons keep things connected. That
connective tissue is usually the weak link. Every time
you work out in the weight room or ride your bike
for five miles or throw 100 throws, you’re getting
stress and getting microscopic tears in the muscles,
tendons and ligaments.
“Stress, mathematically, is force divided by the
area,” Fleisig adds. “Force per area is how hard you’re
pulling that tendon or ligament divided by its cross-
sectional area. So you have big muscles exerting force
and they’re connected to these skinny little ligaments
and tendons, which have a smaller area and will suf-
fer more stress. In repetitive stress, throw after throw
or step after step, your muscles and tendons stretch,
and each time they do, you get little tears in them.”
How much stress does pitching exert on a hurl-
er’s arm? Using a high-speed, three-dimensional au-
tomated motion analysis system, Fleisig and noted
sports surgeon James Andrews computed the stress
on key elbow and shoulder joints during the act of
pitching. When the arm is cocked back, for instance,
the stress on a pitcher’s elbow is 100 Newton meters.
“That’s the equivalent of having five 12-pound bowl-
ing balls pulling down on your arm,” explains Fleisig.
“Unlike a car or other mechanical system, we’re all
living creatures, so we may get these little tears—but
then when we rest or sleep, our body repairs itself.”
It’s crucial that the body has sufficient recovery time.
When a pitcher throws 100 pitches in a game and
then rests for a few days, the body heals its tears. But
if he rushes back to the mound too soon, that’s when
trouble starts. “The second time out, the stress and
tears build upon the previous time’s,” Fleisig says.
“The little tears keep building up faster than they re-
pair. Then you get a big tear and you have an injury.”
That is precisely what’s been happening to pitch-
ers in recent years—at all levels. Indeed, almost 60%
of Tommy John surgeries now are performed on ath-
letes between the ages of 15 and 19. Why? Fleisig, a
member of the Major League Baseball Elbow Task
Force, a research group established to probe this epi-
demic, has studied thousands of young pitchers and
attributes much of the problem to a recent emphasis
on specialization. Traditionally, kids played differ-
ent sports according to the seasons. Now, promising