Crusading for the Balke Protocol

Pediatric Exercise Science, 1999,11, 189-192
0 1999 Human Kinetics Publishers, Inc.
Crusading for the Balke Protocol
It can only be considered a sad commentary on a man's life when he becomes a
passionate advocate for a particular treadmill testing protocol (as in, "Get a life,
Dad!"). But, to quote a 6-year-oldboy who was being complimented for his excellent effort on a recent exercise test in our lab, "A man's got to do what a man's got
to do!" (John Wayne also said this in The Green Berets.)
So, this is a pitch for use of the modified Balke treadmill protocol for clinical
exercise testing in children. It's a Balke because it holds speed stable and increases
work by raising the treadmill slope at regular intervals.It's "modified" because it's
different than Bruno's original protocol, which called for a 3-mph speed with increases in elevation of 2.5% every 2 minutes. And we're pushing it because, after
using it in our laboratory for 15 years, we find it highly successful in achieving
maximal, or at least near-maximal, efforts in young subjects, ranging from the
obese and poorly fit child to the elite distance runner.
The modified Balke is a protocol that is commonly used in the research
setting, but it hasn't found its way into the pediatric clinical testing laboratory. In
fact, we seem pretty much alone on this. In a recent informal survey of 17 pediatric
clinical labs that used treadmill testing, only one other center reported using the
modified Balke. The rest conducted testing with the traditional adult-lab Bruce
protocol, which involves combined inconsistent increases in speed and treadmill
elevation (see Table 1). I suspect the reason for this popularity of the Bruce protocol in pediatric clinical testing is one of inheritance: Such labs grew out of adult
stress testing settings, where "The Bruce" has been a good protocol for evaluating
older, poorly fit individuals with coronary artery disease.
We have never been particularly enthusiastic about the Bruce protocol. To
start with, it changes treadmill speed and elevation at the same time-and with
Table 1 The Bruce Treadmill Protocol (3-Minute Stages)
Stage
Speed (mph)
Grade (%)
190 - Editor's Notes
uneven increments-which can be intimidating to skittish subjects.More importantly,
it begins very slowly (1.7 mph), already at a fairly steep grade of 10%. The standard
Bruce protocol does not get subjects into a run until 15minutes into the test, and then,
just before the subject's head goes through the lab ceiling (18% slope). Much of the
exercise is performed at relatively steep elevations, which forces many subjects to
hold on to the hand rails (which seems to reduce cardiovascularwork and extends the
duration of the test). These characteristicsdo not make this protocol amenable to the
wide range of fitness and age encountered in the pediatric lab. Consider the difficulties, for instance, in testing a state-champion cross-country m e r who comes with
complaints of chest pain and
during training runs. One would have to
order out for pizza waiting for the test to end.
The modified Balke avoids these problems. One selects a comfortable running or walking speed appropriate to the fitness level of the subject. The only
variable altered during the test is treadmill elevation, with uniform increments.
The result is a test conducted at a comfortable, constant speed, without exaggerated slopes, and with an acceptable test duration. In fact, with experience, it is
possible to select treadmill speeds that will cause the test to last 10-12 minutes,
regardless of whether the subject is an elite endurance athlete or an obese, sedentary adolescent.
Here's how we do it. The testing speed is determined by a consideration of
the child's age, body composition, and athleticism, along with identification of a
comfortablepace during the warm-up period. Our treadmill computer has been set
for options of walking speeds of 3.0,3.3, and 3.5 mph as well as running velocities
of 5.0,5.3, and 5.5 mph. We find these will accommodate almost all our subjects7
range of fitness, although occasionally a higher speed is used for an exceptionallytalented distance runner, or slower for a small child (such as a 4-year-old with
complete heart block being evaluated for heart rate response), who usually needs
to hang on to the hand rails.
From research testing, we have found that for all the walking protocols, we
need to start at a 6.0% slope to keep the test from lasting too long, while we start
with a flat treadmill for the running protocols. Increments in elevation are 2.02.5%, and we use 2-minute stages for clinical testing (in which submaximal steadystate is not an issue) (Table 2).
As stated above, we have found that the steady, comfortable speed and lack
of high treadmill elevation with the modified Balke has allowed us to obtain highintensity efforts out of almost all our subjects,regardless of their level of fitness or
their happiness in spending the morning with us. A review of the last 400 clinical
Table 2 Modified Balke Treadmill Protocol (2-Minute Stages)
-
Subject
Poorly fit
Sedentary
Active
Athlete
Speed (mph)
3.0
3.25
5.OO
5.30
--
Initial grade (%)
Grade increment (%)
The Balke Protocol - 191
tests done in our laboratory bears this out. Approximately half were done with
subjects walking (mean age, 12.4 f 3.5 years) and half running (mean age, 14 f
2.4 years). In the combined groups, evaluation of subjects with known heart disease was the most common reason for testing (N = 118, or 30%). Reflecting the
wide variety of indications for exercise testing of children and adolescents, 46
(12%) underwent testing as a provocation for dysrhythrnias, 86 (22%) for shortness of breath, 86 (22%) for chest pain, and 56 (14%) for syncope/dizziness with
exercise.
In the walking tests, the average speed was 3.2 -f 0.3 mph. At "maximal"
exercise, the average slope was 14.9 f 2.6%, and mean test duration was 10.24 f
2.54 minutes. Peak heart rate averaged 186 k 14 bpm. With the running protocol,
the average speed was 5.2 k 0.2 mph, maximal slope 10.2 f 2.9%, and test duration 10.57 +. 2.38 minutes. The average peak heart rate was 194 10 bpm.
In summary, then, we've found this protocol to be highly effectivein obtaining reasonably high-intensity exercise efforts from subjects of all ages and fitness
levels. The explanation seems to be the relatively short test duration, which is
performed at a non-threatening speed and without high slopes that intimidate subjects and cause a need to hold on to the hand rails.
There are some disadvantages with the modified Balke protocol. Unless one
is measuring oxygen uptake, for instance, there is no good way to quantify endurance fitness levels that will allow comparison to established norms (although recognizing the speed and test time of the subject does provide a rough estimate of
aerobic fitness). Using the same protocol in serial testing of a given individual,
however, does provide useful information on changes in endurance fitness. In addition, as with all treadmill protocols, submaximal measurements (blood pressure,
echocardiography) are more difficult. When these are required, we usually use a
cycle protocol.
There are other points that should be made regarding exercise testing protocols in children and adolescents. We use the modified Balke treadmill protocol as
a nonspecific means of examining certain physiological and symptomaticresponses
to exercise stress. In some situations, however, a more imaginative approach may
be appropriate to fit the testing to the patient's complaint. That is, if a girl tells you
she has unexplained palpitations and tachycardia only while climbing stairs, a telemetry-monitored trial of running up flights of stairs makes sense. Or, if sprints
cause chest pain in a hockey player, a protocol involving rapid high-speed bursts
might be more helpful.
It is also critical to emphasize that while the nature of the protocol is important, other considerationsare essential in obtaining good exercise tests in children.
Most importantly, a warm, reassuring approach to the anxious child is necessary.
We sprinkle in bits of fine humor-arguing with my nurse whether I should sing,
for example, or "if you get your heart rate over 200, you'll get a lollipop. Too bad
-yw-wm't
behg-rengxtw~thp.nrixeaextweekwillbe~anana~~expenses~~ddtrip
for you and your family to Aruba." (At this point a parent will most likely say,
"We'll come back!")
As with all protocols, it's important to assure a child's safety, and we accomplish this by having a staff person behind the exercising child at all times. In our
laboratory, the child's size determines who will stand behind him or her. For children 70 pounds or less, I personally take on the task, particularly if he or she is
walking. In heavier, running subjects, I assign this duty to a resident or medical
+
192 - Editor's Notes
student, particularly one who is unmarried, has no children, and possesses adequate health insurance. We have no experience with contraptions such as the safety
hamess Neil Armstrong and his colleagues have used in Exeter, which is suspended
from the ceiling. A slip while running with such a device will leave the child hovering Peter Pan-like in midair, safe but presumably mildly vertiginous.
Over the years in our laboratory we have actually had only one real fall on
the moving treadmill. A rather unfit, overweight adolescent female had reached a
heart rate of about 130 bpm after a couple of minutes of exercise and told me she
was tired and wanted to quit. As she had just started and did not look at all fatigued, I encouraged her to try for "just one more minute." At this point, however,
she decided to take matters into her own hands, giving me a dirty look and simply
stopping-with obvious results. Fortunately, there were no injuries.
Thomas Rowland, M.D.
Editor