By Matt Fitzgerald
On a Hot
Streak
Core body temperature
regulation is not a big issue in most Ironman swims, as cool (and even somewhat
warm) water transfers heat away from the body very effectively. But the bike
and run legs are a different story, especially on hot days. Almost
three-quarters of the energy that your muscles release during cycling and
running takes the form of heat waste. If this heat were allowed to accumulate
in the muscles it would eventually cause serious tissue damage.
Your body has various means
of preventing this heat from accumulating. The best known and among the most
effective is perspiration. But the most effective of all is simply regulating
your exercise intensity. The more you slow down, the less heat your muscles
produce. That’s why you don’t race as fast on hot days.
You might assume that your
core body temperature begins to rise gradually at the beginning of the bike leg
and continues to rise throughout the rest of the race, reaching its highest
level when you cross the finish line. This is seldom the case.
“Within the first 10 to 20
percent of the race, the core temperature rises relatively quickly,” says
Jonathan Dugas, Ph.D., an exercise physiologist at the University of Chicago.
“For example, it might rise from 37.5 to 38.75 degrees C in that timeframe. And
then for the remainder of the event it stays within a very narrow range—maybe
0.1 and 0.2 degrees Celsius.”
The maximum safe core body
temperature is 40 degrees C, or 104 degrees F. Even on the hottest days, Ironman
participants seldom cross this threshold. According to Dugas, that’s because
the brain constantly monitors the core body temperature and produces feelings
of discomfort and fatigue that force you to slow down and generate less heat if
things look like they’re about to get out of hand. Triathletes sometimes
mistake these unpleasant symptoms as indications of heat illness, but they are
actually products of a self-protective mechanism that prevents heat illness.
But this self-protective
mechanism has been known to fail. That’s probably because the brain itself can
become too hot to function properly during exercise in hot environments. When
this happens, the central nervous system begins to malfunction and the athlete
becomes dizzy, disoriented and uncoordinated, and may collapse.
Running
on Empty
The most celebrated
physiological challenge of Ironman racing is supplying the muscles with enough
energy to cover the distance as quickly as possible. The average Ironman
competitor burns more than 6,000 calories between the start and finish lines.
These calories come from
fats stored in adipose tissue and within muscle tissue, glycogen stored in the
muscles and liver, amino acids released from the breakdown of muscle proteins
and calories ingested during the event, usually in the form of carbohydrates.
The balance of fuels shifts
over the course of the day. During the swim and the first portion of the bike
leg, carbohydrates are likely to provide almost half of the muscles’ energy,
with fat providing an equal amount and protein just a sliver. As the body’s
carbohydrate stores decrease, the carbohydrate contribution to forward progress
diminishes and fat takes up the slack. By midway through the marathon, at the
latest, muscle glycogen will have reached critically low levels in the calves,
quads and hamstrings. Consequently, total carbohydrate contribution to
continued running drops further, fat oxidation increases, and amino acids may
provide as much as 15 percent of the muscles’ energy.
The inability to supply
sufficient energy to the muscles is one of the main reasons individuals who do
not train for an Ironman cannot complete an Ironman. Endurance is strictly
limited by the availability of glycogen in the liver and working muscles. When
these stores fall too low, your day is done. Endurance training greatly
increases the body’s capacity for glycogen storage. But even the fittest
triathlete cannot store enough glycogen to fuel an entire Ironman. Thankfully,
training also greatly increases the capacity to burn fats, which allows the
athlete to conserve glycogen, making it last longer.
There’s a
Hole in the Bucket
The most visible effect of
Ironman racing on the body is the production of tremendous amounts of sweat.
Thank heavens for sweat. Perspiration is a vital cooling mechanism for the
body. The blood carries some of the excess heat produced by the muscles during
cycling and running away from the muscles to capillaries near the surface of
the skin, where it leaves the body. Sweat glands then take up some fluid from
the blood, and with it some heat, and release it onto the surface of the skin,
where it evaporates, cooling the skin. Finally, cooled blood flows back toward
the core of the body to absorb and distribute more heat.
The only problem with this
mechanism is that it’s essentially self-sabotaging. The more you sweat, the
more your blood volume shrinks, and the more your blood volume shrinks, the
less heat your circulation can carry away from the working muscles. However,
contrary to popular belief, dehydration only slightly increases core body
temperature. Its greatest effect is on performance, because as your blood
volume decreases, so does your cardiac efficiency, or the amount of oxygen your
heart can deliver to your muscles per contraction.
In a typical warm or hot
Ironman, athletes sweat in excess of one liter of fluid per hour on the bike
and during the run. That adds up to more than 20 pounds of fluid loss for many
athletes! If some of these fluids were not replaced through drinking,
triathletes would not be able to complete Ironman events nearly as fast as they
do. By the time they got to the marathon, their blood volume would be reduced
to the point where walking or a painfully slow shuffle would be the greatest
level of exertion possible.
Even with the availability
of sports drinks and water, most triathletes finish their Ironman races
weighing a lot less than they did when they started. Nevertheless, rather
modest amounts of fluid intake appear sufficient to enable the body to maintain
blood volume, as the body can also draw fluid into the blood from other
compartments (and, for that matter, much of the weight lost during an Ironman
comes from the metabolism of fuels and the release of water stored with glycogen,
which does not contribute to dehydration). A 2007 study from the University of
Cape Town, South Africa, found that while participants in an Ironman triathlon
lost nearly 5 percent of their body weight, their blood volume actually
increased.
Wear and
Tear
Muscle tissue stress may be
the single greatest challenge the body faces in an Ironman triathlon. Vast
numbers of muscle cells are disrupted, damaged and deconstructed along the way.
The main cause of muscle damage is mechanical stress, which is caused primarily
by eccentric (pronounced ee-centric) muscle contractions. In an eccentric
contraction, the muscle lengthens as it contracts (for example, during the
lowering phase of a biceps curl) instead of shortening as in a concentric
contraction (e.g., the lifting phase of a biceps curl) or staying the same
length as in an isometric contraction (e.g., flexing to show off one’s biceps).
The muscle is really being pulled in two directions at once during an eccentric
contraction, like a tug-o’-war, so it’s easy to see the potential for tearing.
A second cause of muscle
damage during exercise is the breakdown of muscle proteins for energy, called
catabolism. Protein is not a preferred energy source during exercise, but when
carbohydrate stores run low in the later portion of an Ironman, protein is
called upon increasingly to take up the slack. As mentioned above, by the end
of an Ironman, protein may supply as much as 15 percent of the energy your
muscles use to keep moving. If you’ve ever finished a long workout or race
smelling like ammonia, that’s a sign you’ve been burning a lot of muscle
protein, as ammonia is a byproduct of protein catabolism. When your blood
glucose level drops during exercise, your adrenal glands secrete the stress
hormone cortisol, which assists in breaking down carbohydrates, fats and
proteins to release energy. Most of the proteins that it breaks down are found
in your muscles.
Muscle damage is also
caused by oxidative stress during exercise. A small percentage (an estimated 2
to 5 percent) of the oxygen molecules that enter the body lose an electron
while participating in energy release in the mitochondria, becoming “oxygen
radicals.” This increases their instability and causes them to pilfer an
electron from a living cell in order to regain stability. The result is often a
chain reaction of “free radical” damage to cell membranes, DNA and various
structural proteins. During endurance exercise the rate of oxygen consumption
can increase up to seven times above resting levels, with a corresponding
increase in the production of oxygen radicals.
Just how much muscle damage
does your body experience over the course of an Ironman? One of the chemical
biomarkers used to estimate muscle damage is creatine kinase (CK), which leaks
into the bloodstream from ruptured muscle cells. According to Bryan Berman,
Ph.D., an exercise physiologist with Carmichael Training Systems, in a
recovered state, the typical athlete’s serum creatine kinase level is
approximately 125 U/L. Twenty-four hours after completion of a half-marathon,
the CK level doubles. A day after a bike ride to exhaustion at 70 percent
VO2max (a little faster than Ironman intensity), CK levels are as high as 700
U/L. And one recent study found that 16 hours after finishing an Ironman, triathletes
had an average serum CK level of 1500 U/L, or more than 10 times the normal
level.
I Think I’m Going to Puke
Australian professional
triathlete Chris Legh had emergency surgery to remove half his colon after the
1997 Hawaii Ironman. A good chunk of the organ had literally died during the
event due to inadequate oxygen supply. While this type of crisis is extremely
rare in Ironman racing, and in Legh’s case was probably related to a congenital
heart defect, completing an Ironman is stressful to the gastrointestinal system
of every competitor. Common problems include stomach discomfort and bloating,
nausea, vomiting and diarrhea.
Exercise scientists do not
fully understand the causes of such symptoms of GI distress during intense
physical exertion. But they have identified some of the contributing factors.
In a 2005 review published in the online International SportMed Journal,
authors Stephen Simons, MD, and Gregory Shaskan, MD, wrote, “To date,
contributing theories mainly focus on the mechanical agitation of the gut,
fluid shifts, decreased splanchnic blood flow, dehydration, increased
sympathetic and parasympathetic tone, endotoxaemia, changes in bowel transit
time, hormone shifts and autoimmune changes. However, none of these adequately
explain the full range of GI pathology.”
Triathletes also bring many
of their GI troubles on themselves by trying to consume too much fluid or
nutrition or foods that are too difficult to digest while competing in Ironman
events. The gastrointestinal system cannot tolerate the same rates and types of
nutrition intake during vigorous activity as it can at rest. Studies have shown
that athletes who take in the most nutrition during endurance events are most
likely to suffer gastrointestinal mishaps.
The final
stretch
If you’ve ever completed an
Ironman, you know that the last few miles of the marathon are a unique
experience that is only hinted at by the experience of running the last few
miles of a regular marathon. Your body is so impaired from the beating it has
taken over the course of the day, it’s almost funny. The simple act of lifting
your foot off the ground to take the next stride feels akin to performing a
heavy squat with a weighted barbell on your back. Research from the National
Institute of Sport and Physical Education in Paris confirms that the energy
cost of running at the end of a triathlon is significantly greater than that of
running at the same speed without swimming and cycling beforehand. And that’s
an Olympic-distance triathlon.
There are probably multiple
causes of the “weightlifting” effect of an Ironman marathon’s closing miles.
Stride form is measurably different at the end of a triathlon run than it is in
the same athletes in an independent run. The stride changes that increase the
energy cost of running at the end of a triathlon are themselves caused in part
by local fatigue in specific muscles, which necessitates a change in form in
much the same way you might start running with a locked right knee to protect a
suddenly cramping right calf muscle. It’s neither efficient nor pretty, but it
sure beats the alternative.
In triathlons and
independent runs alike, fatigue and loss of mechanical efficiency are
associated with increasing ground contact time. The closer you get to the
finish line, the harder it becomes to pry your feet off the road. This bit of
bodily mutiny is caused by a weakening of motor output from your brain to your
working muscles. It is your brain’s way of preventing you from running
faster—and perhaps even forcing you to slow down—in response to feedback from
your body.
Your brain itself may
become tired by the end of an Ironman—a phenomenon known as central fatigue.
Like your muscles, it runs low on critical fuels and accumulates increasing
levels of metabolites that interfere with its functioning, resulting in
feelings of discomfort, loss of will to continue, fractured thinking, declining
mood and reduced ability to fire the motor neurons that activate the muscles.
The
Aftermath
It takes a good while for
the body to recover from the stress of completing an Ironman. An Austrian study
found that blood levels of antioxidant enzymes remained significantly reduced,
while biomarkers of muscle damage and inflammation remained significantly
elevated in triathletes nearly three weeks after they had crossed an Ironman
finish line.
The immune system plays a
major role in helping the body recover after exhaustive exercise, but the
immune system itself is overwhelmed by the stress of endurance racing and its
aftermath. Immune cell function remains depressed for as long as three days
after such an experience, greatly increasing the athlete’s susceptibility to
viral and bacterial infections. The causes of this effect appear to be multiple
and are not fully understood. Part of the problem is that the immune cells’
main fuels, such as the amino acid glutamine, are depleted during exhaustive
exercise. It seems that the immune system also downregulates its inflammatory
response to tissue damage to avoid out-of-control systemic inflammation that
would otherwise result from the high muscle damage incurred. But this very downregulation
impairs the immune system’s ability to fight foreign invaders.
Triathletes also commonly
suffer from a malady known as the “post-Ironman blues” in the weeks after an
Ironman. It is likely that such mood depression is to some degree just another symptom
of the general overtraining syndrome that commonly affects endurance athletes
after such a test. Overtraining is known to disrupt brain neurotransmitters
that influence mood. It has been hypothesized that as a symptom of
overtraining, depression is your brain’s way of discouraging you from
overexerting yourself again—in this case, doing your next Ironman—for a while.
The challenge: Take a
short-course specialist and adapt his training for back-to-back long-course
world championship races, first in Vegas, then in Kona. Age-group triathlete
Kim McDonald tells you how to successfully make the leap to long-distance
triathlon.
Note: This article originally appeared in the April 2012 issue of Triathlete
magazine.
Racing short-course
triathlons is what I’ve done mostly and what I do best. I’ve won two sprint national
championships and an ITU sprint world championship in recent years. But
long-course triathlon is an entirely different beast, one that I had never
quite figured out. Last year, after qualifying for the Ironman World
Championship 70.3 and Ironman Hawaii at Ironman 70.3 California in Oceanside, I
had to put together a real-life training program that would make me competitive
in the two races, yet fit into a 40-hour-per-week work schedule and busy family
life. By the end I’d not only be a better triathlete, but could share some
lessons with other triathletes who, like me, are fast at short-course
triathlons, but are either rookies or consistently underperform at the longer
distances. Herein, some insights and tips gleaned from my own experience:
Identify your weaknesses
and revise your training to improve them early in the season.
Ask yourself whether you’re
doing too much training in the disciplines you’re good at, which is a natural
inclination. I tend to favor swimming and running, as both fit well into my
9-to-5 work schedule and don’t cut into family time like all-day rides. And I
look forward each week to the social aspects of my open-water swims and group
runs. But when I looked back at my race results, it was clear my lack of
cycling was seriously limiting my performance in long-course triathlons. I had
done Ironman Arizona twice and Kona three times in the previous four
years, and my performances in those races were far from stellar. While my
iron-distance swims have ranged from 56 minutes to an hour and my run times are
better than average, my bike times have been embarrassingly slow. Five- to
six-hour rides on Saturdays had helped me bring my Kona bike splits down from
the six- to the high-five-hour time range, but I’d get off the bike in every Ironman
feeling physically trashed, stiff and completely out of contention. I realized
that to succeed at two back-to-back long-course world championships without my
usual “crash and burn” bike legs would require me to come up with a totally
different approach to bike training. I also knew that to be reasonably
competitive in my age group, I had to train myself to run faster half-marathons
and marathons off the bike.
I started by bringing my
bike to work in my car and rode at lunch as many days of the week as I could.
My typical Saturday and Sunday rides, plus the additional rides back and forth
to my daughter’s weekend soccer games (a 45-minute drive away) doubled my
average weekly saddle time from seven to about 14 hours. (My total weekly
training hours stayed in the typical “working man’s” range—usually 20-plus
hours a week for my base and build periods, and 12 to 13 hours for my recovery
weeks.)
Make strength training a
priority.
I also realized that doing
well at longer distances requires much more physical strength than I had
naturally or was able to build from my years of short-course racing. For
age-groupers as well as pros, strength is one way you can get faster with age
in any triathlon distance, particularly in long-course racing. And the early
part of the season is the best time to make major gains in strength. I asked
Siri Lindley not long after she had coached Mirinda Carfrae to her 2010 win in
Kona what she considered the key for success in moving up to the Ironman
distance. Her reply was one word: strength. It’s true.
My weight workouts weren’t
adequately addressing my weaknesses, specifically my lack of leg and core strength—two
things critically important for preventing fatigue on the longer bike and run
legs of an Ironman. I discovered as the summer progressed that holding planks
for two minutes or more were particularly helpful in helping me maintain my
aero position for long periods on the bike. One-legged squats effectively
strengthened the supporting muscles around my quads, glutes and hamstrings that
increased my power on the bike. And regularly pushing a big gear in the aero
position at a slow cadence up hills and into strong winds enabled me to hold my
average speed on long rides with much less fatigue.
Train your brain, too.
Another major shortcoming I
identified from my race results was my inability to stay mentally focused for
five or more hours at a time. To build my mental focus, I backed up my usual
five- to six-hour group ride on Saturdays with a four- to five-hour solo ride
in the aerobars on Sundays, which I’d follow up with a one- to two-hour
moderate-paced solo run. Spending that much time training entirely by yourself
does wonders for your mental focus, believe me.
Work on your nutrition in training.
Work on your nutrition in training.
Plain and simple: Improper
nutrition can very easily derail your race. I’ve long known this, but never
gave it the attention it deserved. If you’re having the same fueling issues
race after race, it might be time to call in the professionals (nutritionist,
coach, doctor).
Don’t keep a rigid training
schedule.
Be flexible and arrange
training around work, vacations and family. To make riding the activity I’d not
only look forward to, but something my family would accept, I made it the focus
of my summer vacations: a week in Flagstaff, Ariz., where I put in 20 hours of
riding in mid-June with friends; a long weekend following the June Lake
Triathlon in Mammoth, Calif., in July; and another long weekend with my
daughter’s soccer team in August in Walnut Creek, Calif., where I managed to
get in a four-hour ride in between games with triathlon legend Dean Harper. To
prepare for the hills and heat of the 70.3 world championship, I also took a
weekend training trip to Sin City at the end of July. My experience riding
around the hilly Lake Mead National Recreation Area and running on the course
led me to plan a conservative race strategy for IM 70.3 worlds—ride in a low
gear on the hills to avoid torching my quads, take the time and effort to stay
hydrated, then build my effort on the run to make sure I didn’t fade in the hot
desert sun.
Races
Race day turned out to be very different than expected—relatively cool with light winds and temperatures that only reached the low 90s. I was dropped early by the lead pack in the swim and reached the shore in 31 minutes, more than three minutes slower than my usual 1.2-mile swim, making me realize the downside of cutting back on my swimming workouts. But I kept to my plan, riding conservatively on the hills and staying hydrated. The first part of my run was hampered by GI problems and three visits to Porta-Pottys in the first loop. But by the second and third loop, I was feeling great and running seven-minute miles. I ran hard and finished seventh in 5:08, the first American finisher in my age group. I figured my strong finish was a good indicator of my fitness for my “A” race—Kona.
I recovered for a week,
then ramped it up again three weeks before Kona with my longest ride of the
summer, a 162-mile, nine-plus-hour bike with one of my regular riding buddies.
I knew that mega-workout—plus another weekend hammerfest two weeks prior when I
rode five hours on Saturday, ran a half-marathon race on Sunday morning, then
got back on the bike for another five-hour ride—would be not only a good
physical test, but prepare me mentally for the tortuous conditions I’d be
facing in Kona.
My taper for the two weeks
leading up to Kona were focused on getting back some of my swim fitness, so I
backed off sharply on my running and cycling, and swam nearly every day to
regain the feel of the water. When the cannon finally exploded over Kailua Bay
for the start of Ironman Hawaii, my swim felt like it was back to normal and I
exited the water in 1:02, about where I expected given the slower swim times
from the day’s ocean currents. The first part of the bike felt easy, and by the
30-mile checkpoint I had ridden my way into first place in my age group. But
stomach problems from the saltwater on my way to Hawi led to GI distress on the
return trip, requiring a pit stop before Kawaihae. I rode back into Kona in
5:33, insixth place with my fastest bike time ever in Hawaii. As soon as I got
off the bike, the GI problems returned with a vengeance, reducing the first 20
miles of my run to a series of sprints, jogs and walks from one Porta-Potty to
another.
I kept positive mentally,
remembering how I felt the previous year when I strained my lower back two
nights before the race and then somehow made it to the finish line. I started
by telling myself I’m on pace for a 10:30 and a podium finish if my legs come
back like they did in Vegas. When they didn’t, I kept going with hopes of a
10:40 finish, then 10:50 and finally, as I ran the last 6 miles as hard as I
could with the hope of breaking 11 hours, finished in 11:04, 11th in
my age group. Not my best performance on the Big Island, but overall I’m pretty
pleased with how things turned out. My bike split in Kona proved my new
approach made a difference and, I believe, will allow me to one day be
competitive in this race. And I’m already getting a head start on my cycling
this season. With enough work, I’m hoping I can eventually turn my weakness
into a weapon.