athletes are often encouraged to zero in on one sport
all year. Compounding the problem is a fixation on
the radar gun, which measures how fast a pitch trav-
els. “It used to be that the pitcher who had the best
stats was promoted,” Fleisig says. “Now the focus is
on who has the best speed. So kids throw as hard as
possible. This max effort, plus doing it year-round,
are the two factors leading to injuries.” Tommy John
himself bemoaned the trend in a recent article for
AARP. “This is about more than just baseball and el-
bows. It’s about the way we’re raising our children.
The nation’s youth-sports industry is a $15 billion
business,” wrote John, now 76. “And kids’ bodies
are paying the price... If a child is spending more
than eight months annually in one sport, he or she
is nearly three times more likely to experience an
overuse injury in their hip or knee.”
Of cOurse, the stress of repetitive motion is a prob-
lem that extends far beyond the baseball diamond—
indeed, it pervades pretty much every human activ-
ity. Running is one of the most obvious. In jogging a
mile, for instance, we take about 1,200 steps, each
one pounding the surface with a force nearly triple
our body weight. “With running, you get two types
of injury,” Fleisig says. “One is something like shin
splints—also common among dancers—from tension
on the tendons. But when you get an injury to the
meniscus—cartilage in the knee—or a bone injury
[such as a stress fracture], that’s from compression”:
the impact of the foot hitting the ground.
In the most extreme cases—say, a 26.2-mile
marathon—running can subject the rest of the body
to punishing stress. A 2017 Yale University study
found that 82% of post-marathon runners developed
stage 1 acute kidney injury (an inability to filter waste
due to elevated levels of creatinine, a chemical waste
product). Although the kidneys recovered within two
days, researchers stated that the cause may be the
sustained rise in core body temperature, dehydra-
tion or decreased blood flow to the kidneys that occur
during a marathon. Additionally, 73% had urine sed-
iments and other injury and repair biomarkers, in-
dicating structural kidney damage. Other effects of
marathoning include perilously low levels of sodium.
Often marathoners see their urine darken post-race.
That’s usually a by-product of muscle breakdown:
muscles stressed to extreme levels release myoglo-
bin, an oxygen-bearing chemical that tints urine dark
brown en route through the bladder. If this all sounds
a bit scary, the good news is that marathon running
can actually, in the long term, make you healthier—
so long as you’ve built up to it slowly. Marathons
are “a massive physical challenge,” sports scientist
Mark Lake of John Moores University in Liverpool,
England, told the BBC. “You’d want to get someone
to gradually train for it over a period of months so
the body has the chance to adapt.”
As many of us know firsthand, you don’t need to be
a jock to suffer the effects of repeated physical stress.The more time we spend on our
devices, the greater our risk
for repetitive strain injuries
like carpal tunnel syndrome,
tendinitis and muscle spasms.