Kettlebells Kick Butt

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1 | March 2013 • ACE CertifiedNews
ACE-SponSorEd rESEArCh
It’s tough to imagine a more archaic-
looking piece of strength-training
equipment. The kettlebell is seriously
old school. Essentially a cannonball
with a handle, iron kettlebells were first intro-
duced in the 1700s by Russian strongmen who de-
veloped techniques of swinging and lifting the orbs as
a way to build strength, balance, flexibility and endur-
ance. As it turns out, the kettlebell must have been way
ahead of its time. New groundbreaking research sponsored
by the American Council on Exercise (ACE) demonstrates that
kettlebell training significantly boosts aerobic capacity, while
also improving core strength and dynamic balance.
THE STUDY
To analyze the fitness benefits of kettlebell training, ACE, America’s
Workout Watchdog, enlisted the research experts at the University of
Wisconsin-La Crosse’s Department of Exercise and Sport Science to con-
duct a full-fledged training study. Led by John Porcari, Ph.D., Nick Beltz,
B.S., and Dustin Erbes, B.S., the research team recruited 30 healthy,
relatively fit male and female volunteers, ages 19 to 25. The subjects
all had some experience with strength training and were randomly
divided into two groups. Eighteen volunteers (9 male, 9 female)
were put into the experimental group, while 12 others (6 male,
6 female) were used as the control group.
Prior to testing, all volunteers participated in two kettle-
bell training sessions to learn correct form for each of
the basic lifts used in the study. To establish a base-
line of strength and fitness, all subjects underwent
an extensive battery of tests. First, they par-
ticipated in a modified kettlebell snatch test
to assess aerobic capacity. The leg press,
upright row and shoulder press were used
KETTLEBELLS
KICK BUTT
BY NICK BELTZ, M.S.,
DUSTIN ERBES, M.S.,
JOHN P. PORCARI, PH.D.,
RAY MARTINEZ, PH.D.,
SCOTT DOBERSTEIN, M.S.,
AND CARL FOSTER, PH.D.

2 | March 2013 • ACE CertifiedNews
to assess grip, core and muscular strength. Finally, flexibility and
static and dynamic balance were tested and each subject’s body
composition was determined using skinfold measurements.
After the exhaustive pretesting, the 18 volunteers from the
experimental group began an eight-week training period. Twice
a week, the subjects participated in an hour-long kettlebell
class led by a pair of certified trainers. Each class began with a
5-minute active warm-up before moving on to 30 to 45 minutes
of kettlebell exercises, including one- and two-handed swings,
snatches, cleans, presses, lunges and Turkish get-ups. Each class
concluded with a 10-minute cool-down period. At the beginning
of the study, the trainers encouraged participants to use a kettle-
bell weight that felt manageable and then progress to heavier
weights as they felt more comfortable with the movements.
Following the eight-week training period, the subjects’
strength and fitness were retested using an identical battery
of assessments as was used in the pretesting.
THE RESULTS
In addition to the predictable strength gains,
kettlebell training was also shown to mark-
edly increase aerobic capacity, improve
dynamic balance and dramatically
increase core strength.
“When most people think of
resistance training, they don’t think
of being able to increase the aerobic
capacity,” says Dr. John Porcari, head of
the University’s Department of Exercise and Sport Science.
“Yet, we saw a 13.8 percent increase in aerobic capacity.”
The most dramatic increase in strength came in abdominal
core strength, which was boosted by 70 percent. Meanwhile,
dynamic balance (in the posterolateral direction) showed
a significant improvement.
In all, compared to the control group, those
subjects who completed the kettlebell
training showed significant improvements
in V
•
O2max, leg press, grip strength,
dynamic balance and core strength.
Researchers saw no significant
changes in body composition
(body weight, sum of skinfolds and
percent body fat) for either group
over the course of the study. Similarly,
there were no significant differences in
HRmax, sit-and-reach, shoulder raise, trunk
hyperextension, shoulder press or static balance in either
group (Tables 1 and 2, see the next page).
THE BOTTOM LINE
“Kettlebell training increases strength, which you’d
expect, but you also get these other benefits,” says Porcari.
“You don’t really do resistance training expecting to get
an aerobic capacity benefit, and you don’t do resistance
training and expect to improve your core strength, unless
of course you’re specifically doing core-strengthening exer-
cises. But with kettlebells you’re able to get a wide variety
of benefits with one pretty intense workout.”
To put into perspective kettlebell training’s potential
to increase aerobic capacity, Porcari says, “If I was to
put someone on a running program, we would likely see
a slightly higher, bigger improvement, but these results
showed cardio improvements that would be better than a
walking program and more in line with what you’d expect
from a regular cycling program. In regards to intensity, it’s
kind of a cross between circuit weight train-
ing and running.”
Researchers also point to the posi-
tive implications of being able to
increase core strength by 70
percent, especially for the
aging population. “I think
that’s huge because the stronger
people are through the core, the
less low-back pain they are going to have,” Porcari
says. Similarly, the gains in dynamic balance have
major positive implications. “Older people who are doing
some sort of kettlebell-like training are going to be more
likely to avoid dangerous falls,” he says.
“And on the other end of the spectrum, for
athletes, the better your dynamic bal-
ance, the better your ability to balance
when you’re moving and cutting and
doing other athletic movements.”
The bottom line is, kettle-
bells may be decidedly old
school, but thanks to the
explosive, total-body nature of
kettlebell training, its potential
for serious body benefits are just
as strong as ever.
KETTLEBELL SMARTS
• “It’s a great workout, but you
really need to get proper instruction
before you do it,” says Porcari. “Good form
is key to avoiding injury.”
• Get a minimum of two to three training sessions
with a certied instructor.
• Always lift with your legs, never your
back. Consider using a workout
video to follow along with for
proper form.

3 | March 2013 • ACE CertifiedNews
This study was funded solely by a grant from
the American Council on Exercise (ACE).
Table 1
Changes in Body Composition, Flexibility and
Balance Over the Course of the Eight-week Study
Variable Pre-test Post-test Change
Weight (kg)
Experimental
Control
71.5 ± 13.18
68.3 ± 15.18
71.6 ± 13.59
68.8 ± 15.20
0.10
0.50
Sum of Skinfolds (mm)
Experimental 47.4 ± 15.63 47.3 ± 14.92 –0.10
Control 45.7 ± 15.15 46.9 ± 16.51 1.20
Body Fat (%)
Experimental 16.3 ± 6.62 16.3 ± 6.25 0.0
Control 18.5 ± 4.77 18.8 ± 5.10 0.3
Sit-and-Reach (cm)
Experimental 32.9 ± 7.93 32.9 ± 7.98 0.0
Control 35.3 ± 6.50 36.0 ± 6.73 0.7
Trunk Hyperextension (cm)
Experimental 42.9 ± 5.39 43.4 ± 5.16 0.5
Control 39.6 ± 5.00 40.5 ± 4.13 0.9
Shoulder Raise (cm)
Experimental 29.6 ± 15.68 27.3 ± 14.8 –2.3
Control 23.2 ± 11.60 22.7 ± 9.47 –0.5
Static Balance (sec)
Experimental 17.4 ± 10.02 16.7 ± 9.42 –0.7
Control 14.0 ± 15.76 15.2 ± 11.59 1.2
Dynamic Balance Anterior (cm)
Experimental 59.0 ± 5.51 60.4 ± 7.41 1.4
Control 61.5 ± 6.80 60.3 ± 6.28 –1.2
Dynamic Balance Posteromedial (cm)
Experimental 64.4 ± 7.72 73.0 ± 7.26 8.6*#
Control 71.1 ± 8.30 74.9 ± 8.09 3.8
Dynamic Balance Posterolateral (cm)
Experimental 67.2 ± 6.33 74.4 ± 7.59 7.2*#
Control 71.8 ± 8.85 74.6 ± 9.80 2.8
*Signicant change from pre- to post-testing (p<.05)
#Change signicantly different than control group (p<.05)
Table 2
Physiological Responses to Kettlebell Training in the Experimental (n=17)
and Control (n=11) Groups Over the Course of the 8-week Study
Variable Pre-test Post-test Change
V
• o2max (mL/kg/min)
Experimental 36.3 ± 5.42 41.3 ± 6.20 5.0*#
Control 37.5 ± 7.97 38.8 ± 7.49 1.3
Maximal HR (beats/min)
Experimental 184 ± 13.8 190 ± 8.5 6
Control 179 ± 18.1 181 ± 16.9 2
rEr
Experimental 1.10 ± 0.105 1.24 ± 0.079 0.14*
Control 1.08 ± 0.115 1.13 ± 0.106 0.05
Shoulder Press (kg)
Experimental 20.3 ± 7.08 21.3 ± 6.33 1.0
Control 17.1 ± 7.03 18.0 ± 6.86 0.9
Leg Press (kg)
Experimental 281.7 ± 92.54 323.4 ± 104.11 41.7*#
Control 239.9 ± 95.80 245.3 ± 95.10 5.4
Row (kg)
Experimental 40.8 ± 12.36 42.8 ± 11.92 2.0
Control 38.2 ± 11.36 41.6 ± 11.53 3.4*
Grip Strength (kg)
Experimental 19.0 ± 5.29 20.7 ± 5.33 1.7*#
Control 18.2 ± 5.60 18.2 ± 5.93 0.0
Prone Plank (min:sec)
Experimental 1:05 ± 0:30 1:50 ± 0:30 0:45*#
Control 1:01 ± 0:30 1:12 ± 0:31 0:11
*Signicant change from pre- to post-testing (p<.05)
#Change signicantly different than control group (p<.05)