CYCLING PERFORMANCE TIPS
Last updated: 1/1/2019
HEART RATE MONITORS
The Heart Rate Monitor (HRM) is touted by many cyclists and trainers as the most
significant training advance in the last ten years. Although many coaches refuse to
work with an athlete without the physiologic training information it provides, HRMs have
their detractors. And that small backlash is slowly growing. An alternative to a HRM,
not quite as technical and rigid, uses perceived effort as
a measure of your level of exertion.
- Basic cardiovascular physiology
- Pros and cons of using a heart rate monitor
- Calculating your maximum heart rate
- Heart rate training zones
- Training tips using a heart rate monitor
- Resting heart rate
- An opposing opinion
BASIC CARDIOVASCULAR PHYSIOLOGY
First, let's review the basic physiology of the circulatory system asking ourselves the
question "What does the heart rate really indicate?" The components of the
cardiovascular system are:
With every heart beat (contraction of the heart pump), a certain amount of blood
(stroke volume) is pushed through the system. The contraction frequency of the heart
is the heart rate (HR). The amount of blood moved to the cells of the body every minute
is the product of the heart rate and stroke volume (HR x strove volume).
- the heart (the pump)
- the arteries (a distribution system)
- the capillaries (the exchange system where gases, nutrients, and other chemical
compounds move to and from surrounding tissue
- the veins (which are the return circuit)
With physical activity (exercise) more oxygen is required by the muscle cells, and the
circulatory system responds by increasing the heart rate (and the cardiac output). With
aerobic training, the actual amount of blood pumped per heart beat (stroke volume)
increases and the efficiency of the exchange process at the capillary level improves.
The result is a lower heart rate for any level of physical activity in the trained
versus the untrained individual. Thus aerobic training benefits include:
The training effect results when the heart muscle is "stressed" by an increase
in cardiac output (just as muscles in the arms and legs respond to the stress of lifting
free weights). As the cardiac output is directly proportional to the heart rate, a heart
rate monitor (HRM) can be used to structure and monitor an aerobic training program. (For
additional background see Basic Exercise Physiology - the
- a lower resting heart rate
- a lower heart rate for a specific level of exertion
- an increased exercise capacity at an individual's maximum heart rate.
The emperor may have no clothes. Anyone who has ever trained for aerobic and
sprint sports has heard about heart rate training zones. They imply a scientific
precision that may in fact be no more than marketing (by trainers, physicians,
and the heart rate monitor industry.) It may be similar to the story of
the 10,000 step craze. Where diD that number come from? A controlled study? A review
of the health of populations?
No, it came
from the advertising department of the pedometer manufacturer who needed
to develop a market for their product.
In fact, the
controversy begins with the simple (you would assume) idea of a standardized maximum heart rate.
Training requires applying physiologic stress, and to apply appropriate stress (enough to
improve, but not enough to increase the risk of injury) you need a metric.
But what is the best metric?
The idea of a scientific number (heart rate and heart rate zones) was appealing. But
anyone who has compared perceived exertion and heart rate zones has found that they
often diverge. That is probably because heart rate at any specified level of exertion
can be influence by many factors - room/air temperature, clothing, training status,
anxiety, level of exercise recovery, and caffeine use, to name just a few.
Perceived exertion makes a bit more sense as a metric. As an embodiment of the
"central governor" it reflects heart rate, levels of lactic acid, the levels of
various hormones, our emotional state, glycogen reserves, and where we are
in our recovery from a prior ride. A much more robust gauge, and why,
"...many trainers and exercisers prefer the RPE scale."
Training requires identification of a target for improvement. What are our targets?
You hear a lot about improving the efficiency of fat as a fuel, but I contend that
comes along for the ride - a freebie as an integral part of improving our LT.
And I am not a believer that eating
a carbohydrate deficient diet improves that any further.
- The musculoskeletal system - strengthen the muscles, ligaments, shoulder muscles,
and skin on the butt to endure long hours on the bike.
- The cardiovascular system - improve the heart's stroke volume and increase the
number of capillaries in the muscles to improve oxygen delivery.
- The removal of byproducts of metabolism - lactic acid and other acidic products of metabolism.
So we really we have just have 3 training zones which are easily identified
using a perceived exertion metric:
"After only a few training sessions you will be accustomed to the RPE feeling
and will no longer need to know your HR. By using only RPE you are not limited
to knowing your HR and can modify your training intensity based on how you feel.
This becomes increasingly important when exercising outside in hot and humid
environments and when you are exercising for long periods of time. Once you
know what a 14 - 17 on the RPE scale feels like, you can exercise anywhere,
on any piece of equipment, and be confident you are in your optimal training zone."
- Moderate- the recovery ride. Usually in the range of 50 - 60% MHR (or %VO2max).
The rate at which we do most of our very long rides to "build up endurance".
- Strenuous - rides at our LT for 30 minutes to several hours. These improve
the total work we can do over a set period of time and translate into
improved times for longer rides. And as the LT increases as we ride,
the %MHR as a metric is a moving target.
- Sprints - all out intervals at our MHR (VO2max) for 30 second which
encourages CV improvement with vascularization of the muscle. I don't
think a HR monitor or zones provides me, personally,more helpful
information than just using PE, once I have dialed in my own awareness to
how hard I am working. Several quotes say it as well as I can:
"Dr. Fritz Hagerman, an exercise physiologist at Ohio University, said he had learned
from more than three decades of studying world class rowers that the whole
idea of a formula to predict an individual's maximum heart rate was ludicrous.
Now let's look at a few of the pros and cons on the use of a HRM.
PROS AND CONS
The ADVANTAGES of a HRM include its use:
The DISADVANTAGES of a HRM are:
- as a motivational tool - like a coach ; brings objectivity to a training program.
- to teach beginners to read their bodies and avoid anaerobic overtraining.
- to aid in doling out energy during time trialing or climbing, saving some for the
- to analyze race efforts and design a personalized training program.
- to spot overtraining (heart rate 10% higher than normal on awakening for several
- its inconsistency - at the same heart rate you're not always putting out the same
effort day to day.
- the lack of scientific support - there is no evidence training with a HRM improve
- too much data, esp with elaborate HRMs, with little agreement on how to use this
information to improve training or performance.
- the lag time in heart rate response to a change in exertion - 15 to 30 sec lag with
2 to 3 min to stabilize at the new level of exertion.
- its incompatibility with group training.
- it distracts from dangerous road hazards.
Here are some definitions you'll encounter in the literature on heart rate monitors:
* Determining your actual Anaerobic Threshold (synonyms are lactate threshold, AT, LT,
Concini test). Accurate laboratory determination of your anaerobic threshold requires
frequent blood draws while pedaling an ergometer at steadily increasing workloads. But
for training purposes, the following approach is an alternative. Using a single gear,
start cycling at 35 kph. Slowly increase speed on a flat course by 1km/hr every 300
meters (1/5 mile). Chart heart rate vs speed. Anaerobic Threshold is the
"breakpoint" where heart rate levels off relative to speed.
- bpm = beats per minute
- Max HR (MHR) = maximum heart rate (expressed in beats per minute)
- target heart rate = the training heart rate (usually a range of values)
- anaerobic threshold (AT)* (synonymous with lactate threshold).
Lactate production occurs with muscle cell activity and increases as activity becomes
more vigorous. Lactic acid is metabolized by the muscle cells, but at some point they
cannot eliminate (or oxidize) the lactate as fast as it is being produced and the blood
lactate level begins to increase. In trained athletes, this threshold for lactate buildup
occurs at a higher activity level or percentage of the athlete's MHR or aerobic capacity.
For all practical purposes, the AT is the highest heart rate you can maintain for a race
or hard ride lasting up to an hour. As the AT increases with aerobic conditioning, it is
considered one of the standard measurements to track training. The AT is usually reached
at 80-90% of your maximum heart rate, but in elite riders rises to 90-93% of their maximum
heart rate.(See also Basic Exercise Physiology - measures
of cardiovascular fitness.)
- lactate threshold (LT). See anaerobic threshold.
Let's assume you have decided to use a heart rate monitor in your training program.
The first step is calculating your MHR or maximum heart rate.
CALCULATING YOUR MAXIMUM HEART RATE (MHR)
Interest in the Maximum Heart Rate is based on the fact that it is a readily
available surrogate for VO2max, the gold
standard for assessing maximum exercise capacity and designing training
I'm sure that at some point you have heard the mantra "MHR is 220 minus your
age in years". However this is just a rough figure and much less accurate than
a real life, on bike, determination. I ran across the following
which not only goes into detail about the various studies supporting MHR
determination, but also provides a calculator that will serve you better
than the 220 - age in years. After reviewing the various studies, they
suggest the following calculation (quoted directly from the website).
To determine your maximum heart rate you could use the following,
which combines the Miller formula with the research from Londeree and Moeschberger.
Just as we all vary in height and body habitus, everyone has their own
personal maximum heart rate that is genetically "hardwired".
Our maximum heart
rate generally decreases one bpm (beat per minute) per year we age. Although
the MHR of a teenager might be on average 220 beats per minute, for an
individual this can vary +/- 11 beats per minute from that average (209-231 bpm).
The same variation holds true as we age. Thus a 40 year old who would be
expected to have a MHR of around 180 (220-40) could vary from 169
to 191 as his or her own personal MHR.
- Use the Miller formula of MHR = 217 - (0.85 x age) to calculate MHR
- Subtract 3 beats for elite athletes under 30
- Add 2 beats for 50 year old elite athletes
- Add 4 beats for 55+ year old elite athletes
- Use this MHR value for running training
- Subtract 3 beats for rowing training
- Subtract 5 beats for bicycle training
Can you slow the inevitable age related decrease in MHR? Although it has traditionally been
taught that an individuals MHR is genetically hard wired (within a certain range)
and your personal MHR will decrease with age, a recent study suggests that
we may be able to blunt the aging effect by maintaining our cardiovascular
fitness with regular exercise. You can
read Dr.Mirkin's take on this study. Bottom line: "Use it or lose it" once again appears
Maximum heart rates are "sport specific"
i.e. they vary from one sport to
another. Thus you cannot use your maximum heart rate from running to plan a
cycling training program without risking overtraining. Cardiac hemodynamics
and maximal sympathetic drive are influenced to some degree by 1) body
position during exercise and to a significant degree by 2) muscle mass
involvement. If an activity is restricted to upper-body muscle mass, peak
heart rates will generally be considerably lower than in whole body
activities (more muscle mass involved). For example, a triathlete with
a max heart rate during running of 180, may only hit 176 on the bike,
and 171 during swimming. To keep our terminology clear, it would be best
if we call the running heart rate the "Maximal Heart Rate" and the highest
heart rates observed in cycling and swimming, "Peak Heart rates for each
event. Knowing your peak heart rate for each discipline helps you to more
accurately structure the intensity of your training.
Identifying your peak heart rate will help you identify your aerobic
threshold for a particular sport. Trying to increase, or train, at your
peak heart rate may lead to injury and over training. Finding your peak
heart rate for each sport you are training for will help you set up your
target zone heart rates (see next section) making your training more efficient.
The only limit to the length of time one can ride at 100% of their MHR
is personal discomfort. This level of activity does not "strain" the
heart muscle or have other harmful effects on the heart itself. Although
this level of activity might be considered in a competitive race or event
for a short sprint, maximizing the benefits of a training program is the
result of a mixture of recovery and hard days.
It is much more productive (in improving your cycling performance) to focus
on how long you can hold your aerobic threshold rather than tiring yourself
trying to improve your peak (maximum) heart rate. Your aerobic
threshold (or lactate threshold) is about 12 beats below your
maximum (84-90% of your MHR). Training at your aerobic threshold is
useful because this is the pace you race at and can be sustained for 30
minutes or longer depending on your fitness. As the time you can hold 100% MHR
is considerably shorter than the time you can ride at 84-90% MHR, the art
of racing is finding the right mix to get you to the finish line first.
If you are interested in finding your personal peak (maximum) heart rate
for cycling, the following on bike approach will give you that number. If
you are overweight or have a family history of heart disease I'd suggest
that you talk to your family physician or consult a cardiologist first.
Actual MHR - Warm up thoroughly (15 minutes on the flats). On a long,
steady hill (doesn't have to be steep) increase effort every minute for at
least 5 minutes until you can't go any faster (sitting, not standing).
Then sprint for 15 seconds (it is OK to stand at this point). Stop, get
off the bike (this is for safety reasons - not mandatory) and immediately
check your heart rate, which should now be at its maximum. Count the
number of beats for a full 30 seconds - then double that number (the
doubled number should be your peak heart rate for bicycling in beats
per minute. Similar results can be obtained on a stationary trainer.
A Reader's Question:
Q. I am a 69 year old male cyclist, ride 3/4 times each week, and ride 180/200
miles over the week. covering up to 180/200 averaging 16 mph over undulating terrain.
Steep short hills I can kick over however long steep or long climbs I get into the red!
My worry is that my heart rate which averages around 142 bpm on these rides top out at 180.
Obviously this is well over the recommended 220 - 69 = 151!
I have no real problems with the high rate but it does concern me if this is causing
too much stress on my heart. I recover after the efforts fairly quickly. As yesterday I kept
with the group over a 10k steady climb but heart rate was at 176. Over the top it took
2/3 minutes to get back down to my usual rate of 130/140 bpm. Continuing to complete
a 112k ride over 4 hours and 8 min? Your comments and advice would be appreciated.
- I do not think you can over stress your heart without some warning from your body
that you are reaching your limits - either chest pain or shortness of breath to a
degree that you would have to slow down.
- The use of 220 minus your age for maximum heart rate is not reliable.
on MHR is well researched and is,
I think, a definitive commentary on Maximum Heart Rate. To quote from their conclusions:
"...the most accurate general equation is ... HR max = 205.8 - (0.685 x age)." With a standard
deviation of 6.4 bpm. (For those of you not used to statistics and standard deviation, SD
is calculated in a way that 99.7% of a population lie within the mean + or – 3 standard
deviations.) So 99.7% of 69 year olds could have a MHR as high as:
and still be within "the normal" range. Basically you are at the upper limits of
the wide normal range. This wide variation means each individual needs to measure their personal
MHR and calculate their own personal training zones from it. That being said, there
is still enough variability from day to day that even that personal approach to using
MHR is much less precise than using a power meter (watts of output) to structure training zones.
- (205.8 - (0.685 x 69) + (3 x 6.4) =
- (205.8 - 47) + 19.2 =
- 159 + 19 = 178
- The rapid return towards normal of your MHR is a another example of how MHR can be used
in training. From
Dr. Mirkin.com "...A healthy person's heart rate drops about 20 beats in one minute after all-
out exercise, while fit athletes' heart rates can drop more than 50 beats in one minute." So it
sounds as if you are well within that 20 bpm limit as the HR fell while still riding with the
group (rather than stopping.)
HEART RATE TRAINING ZONES
There are 5 training "zones" or heart rate ranges. These are arbitrary
divisions and can differ from article to article or coach to coach. They are based on the
fact that there is an increase in heart rate (and cardiac output)
as the oxygen consumption of the exercising muscle increases, and the concept
that there are benefits of applying variable stress to develop exercise tolerance in
heart and skeletal muscle.
Metabolically, as exercise intensity increases and one moves up
from one training zone to the next, there is a shift in the energy source
for the skeletal muscle cells from fat to carbohydrates - below 70% MHR, fat is
utilized preferentially. As MHR is approached, there is another shift towards
anaerobic (without oxygen) metabolism which adds an increase in
lactic acid production to the equation.
The Heart Rate Intensity Zones are generally divided as follows:
If you always train at low heart rates, you will develop endurance
with no top end speed. Conversely if you train hard most of the time, you'll never
recover completely and chronic fatigue will poison your performance. The solution is
to mix hard training with easy pedaling in the proper proportions.
- Zone 1 65% of MHR (recovery rides)
- Zone 2 65-72% of MHR (endurance events)
- Zone 3 73-80% of MHR (high level aerobic activity)
- Zone 4 84-90% of MHR (lactate threshold(LT,AT); time trialing)
- Zone 5 91-100% of MHR (sprints and anaerobic training)
I'd suggest that the optimal approach is to train below 80% of maximum heart rate
(zones 1 to 3) on your easy days to build your aerobic base and is at a low enough
stress level to facilitate muscle recovery. And then, when you have a good training base,
push training to include several days a week above 85% MHR to improve your high
level performance. But avoid training in
the no man's land or mediocre middle at 80-85% of MHR where it's too difficult
to maintain the pace for the long rides needed to build endurance, but
not hard enough to significantly improve your overall aerobic performance and
increase your lactate threshold.
Training programs should be individualized, but once a good base is developed early in
the season within Zones 1 and 2, most programs conform to the following general
TRAINING TIPS USING A HEART RATE MONITOR
- one long recovery ride at zone 1 or 2
- one long day (to be at event distance + 10 to 20%) at the MHR you have planned
for the event. If it is an endurance event, that might be 70% MHR,
and if a time trialing event, 85 - 90% MHR.
- For example: If you are aiming towards a 20 mile race, take 10 - 20% of the event
distance, add it to the event distance which then gives you 22 to 24 miles
at 70% MHR for an endurance event and a target HR of 85 - 90% MHR for a time trial event.
- three high intensity days in zone 4
- one or two interval workout days (which will be
counted as one of the three high intensity zone 4 days. These interval
days could be structured as follows:
- warm up at zone 1 heart rate
- 20 min at zone 3
- 5 min at zone 4
- 7 intervals - hit 90% MHR, then recover until you are back to 60 - 65% MHR
- 5 min at zone 4
- 20 min atone 3
- warm down at zone 1
- the sixth and seventh days of the week can be rest days off the bike or (very)
slow recovery rides at a zone 1 or 2 level of exertion to stretch out your muscles.
USING A HRM TO AVOID OVERTRAINING
A heart monitor can provide you with clues as to whether you are risking an overtraining situation -
and thus should take an extra day of rest. Do a warm up that takes you to the foot of a
familiar hill. Climb at your usual pace while keeping one eye on your HRM. One of four things will happen:
- Heart rate is higher than normal and legs feel tired
- Heart rate is normal and legs feel tired
- Heart rate is higher than normal and legs feel good
- Heart rate is normal and legs feel good
In the first situation, your recovery from previous rides isn't close to what it should be.
Head on home and take the day off. Pushing on will only put you in a deeper hole. In the
second and third scenarios, your recovery is incomplete, but not to the extent of #1.
You can continue riding, but only if you can keep distance and intensity moderate. Scenario
number four indicates you are right on schedule with your training.
Your resting heart rate (RHR) is another indicator of your degree of
training (and monitor for moving into an over trained state). As you train, your resting
heart rate should fall as a result of the
increased efficiency of the circulatory system. The heart will increase the volume of
blood pumped per beat, and the peripheral muscle cells will become more effective at
extracting oxygen from the blood passing through their capillary networks. The RHR for
an untrained individual is 60 to 80 beats per minute. With training, it is not uncommon
to see the RHR fall into the high 40s or low 50s. And as mentioned above, regular
monitoring of your resting heart rate in the mornings (before getting up and beginning
your daily activities) can be used as a monitor for
overtraining (heart rate on awakening and before getting out of bed 10% higher than
your personal normal for several consecutive days).
SLOW HEART RATE
A slow heart rate is considered a sign of good health. As one conditions, the heart will
beat more slowly for any specific level of activity - including at rest. That is why the
resting heart rate is a good measure of cardiovascular conditioning. The two exceptions
are hypothermia, where a slow heart rate is a reason for
alarm, and the other is a heart rhythm disorder. The latter can indicate heart disease,
generally comes on quite suddenly, and is occasionally associated with an irregularity
of the pulse.
AN OPPOSING OPINION
But there are differences of opinion on the usefulness of a heart rate monitor for
training and competing. So keep an open mind and don't consider the HRM as the only
real key to success. The following is from an Aussie coach, Graham Fowler:
"I have observed a number of different %max heart rates during time
trials. My nephew once rode a junior nationals ITT at 100%MHR. He didn't
win it needless to say however didn't crack either. Obviously he was very
fit or his MHR was inaccurate. I advise riders to ride just above (1 to
5 beats per min) what they consider threshold. This is around 92%max hr.
This mark needs to be derived in training. I am aware of race day
anxiety causing the heart rate to elevate somewhat so the hr is not such
a good measure with an anxious rider. I am more inclined in the future
the train with heart rate to establish a perceived effort (pe),
and then remove the heart rate meter during racing and ride on pe alone.
THE BOTTOM LINE
The following question may help to illustrate a few points.
Q. I am 48 years old and a new MTB biker. I am working to keep/improve
my shape in a controlled way, so I am using a HR monitor on my MTB bike.
Until now I used Max HR of 180, just because quite often I reached this figure.
Last time after accelerating my HR for 15 minutes, on a mountain steep trail
I reached (for more than a minute) a HR of 182 -185 (in total it was 3 minutes
of 8.7% trail with avg. speed of 8 km/h, avg. HR of 178 and max of 185) and I
could continue without a problem with the trail.
My questions are:
- Should I consider my Max HR as 185? or what should it be?
- As it is quite far from my theoretical Max HR, what does it mean: Am I in good shape?
Not in good shape? Means nothing (just genetic)?
A. Here are a few thoughts-
Q. I am going to be training for the Paris Brest Paris in 2011 and would
like to know how I can use heart rate or perceived exertion information
to improve my training. The pace of brevets is only an average of 9.5 mph
in order to get under the time cut off. Do you think need a HRM? M.M.
A. PBP is the ultimate endurance event. So cardiovascular training is
not going to be the challenge as much as your musculoskeletal conditioning.
You will probably be riding at 50 - 60 % VO2max most of the time and
thus are burning a fair amount of fat calories as opposed to sprint type events.
So no need to worry about intervals, and in fact as you are going to want to
train at most somewhere around 70 - 75% VO2 max., I would go for "perceived
exertion" that is "how you feel" as the best barometer. A HRM might drive you
to do more than is necessary - and lead to burn out if you are only focused on
training to the numbers.
ABOUT MAXIMUM HEART RATE (AND THE USE OF HRMs)
For decades, the holy grail of training tools for the amateur athlete lacking
access to a sophisticated lab was the heart rate monitor (HRM). Although
maximum heart rate (MHR) was touted as THE way to monitor your recovery, lactate threshold,
as well as design your heart-rate training zones, the numbers are not as precise we might hope.
A number of variables (level of fitness, the ambient temperature i.e how hot it is, the status of
recovery from prior rides, how much stress you’re under that day i.e performance anxiety) all
modify your heart rate for any level of activity.
The referenced article from bicycling.com points out 5 common myths that highlight the weakness of a HRM as a training tool.
So there you are. A few myths about heart monitors and MHR specifically. And remember,
you don't need a gizmo to measure exertion (power meter, heart rate monitor) to give
structure to your training program. Perceived exertion is easy and just as effective.
- "If You Go Over Your Max HR, Your Heart Explodes". If you have normal coronary arteries
and none of the unusual congenital heart abnormalities which can cause rhythm problems
in athletes, the body monitors itself quite effectively to prevent irreversible
damage from excessive exertion. Although one can maintain a supra-maximal effort
for a few minutes before your "central governor" takes over and limits further
exertion at that level, there is no permanent damage from “going too hard for too long.
The reason one limits time at MHR (or a percentage of MHR) is to gain maximum training
benefit (longer is not better) as well as to avoid the real risk of burnout from overtraining.
- "Your Max HR Is the Same For Everyone Your Age". Maximum heart rate varies from individual
to individual and is genetically determined for each of us. It cannot be increased by more
training. And a higher MHR does not determine the upper limit of aerobic performance. There
are many variables that define maximum performance including the amount of blood pumped per
heart beat (stroke volume), pulmonary efficiency (oxygenating the blood in the lungs), removal
of oxygen at the capillary/cell membrane interface by the exercising muscle. And to a great
degree it is how long one can maintain their MHR (which can be increased with training) that
defines award wining performance.
- "Heart Rate Is A Measurement Of How Hard You're Working". Your heart rate increases
with the amount of work being done by your muscles, but lags behind the actual level of
work at any given moment. That lag is one reason a HRM is not a great tool to track maximum effort.
A power meter (watts produced by muscle activity) or perceived exertion are better tools to
define your level of exertion (and stress being put on the muscles) than are tracking the
numbers or your heart rate training zones. This is not to say HR numbers are of no use, but
they are much less precise than adding a few extra watts measured on a power meter as part
of a training interval program.
- "If I'm Not Working at My Max Heart Rate, I'm Not Working Hard Enough". Your maximum
heart rate is not the number you should train to every day. It reflects maximum, or at
least close to maximum, effort. And if you worked at this level everyday you would quickly
burnout with an overtraining syndrome of some sort. Your training should be a balance of
maximum effort (intervals) 2 - 3 times a week interspersed with recovery rides and endurance
rides of longer distances at a more moderate pace. These less intense training days can be
paced using heart rate zones (a % of MHR).
- "As Long as You're Working Under Your Max, You Don't Have to Worry About a
Cardiac Incident". If you have a history of heart disease or risk factors (high blood
pressure, family history, or diabetes are a few examples) exercising below a certain
work thresholds do not protect you from a heart attack. Heart attacks happen at all levels
of exertion and if you are worried, you should have a stress treadmill before undertaking
any exercise regimen.
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