Immunoglobulins, and Running by Pete Pfitzinger -
Pfitzinger Lab Report
You run the best track workout of
your life. Four repeat miles, and you feel like Moses Kiptanui. You hang around
in your sweat-drenched clothes, talking splits with the other runners, and
savoring the atmosphere. The next morning you wake up with the Russian Army
marching down your throat. You have the flu.
Did the track workout suppress your
immune system and allow you to get sick?
The answer is not clear-cut. The
immune system is a complex blend of lymphocytes, leukocytes, immunoglobulins,
eosinophils, natural killer cells, and other beasts, each with its own unique
role in protecting our bodies from disease. Recent research from McMaster
University in Ontario, however, provides some interesting insights into running
and your immune system.
In a study published in the August,
1995 issue of Medicine and Science in Sports and Exercise, Dr. J. Duncan
MacDougall and colleagues investigated the effects of training on the immune
systems of distance runners. Unlike previous studies, MacDougall's group looked
at the effects on the immune system of increasing training volume and/or
intensity, and at both acute (immediate), and chronic (longer-term) effects. I
contacted Dr. MacDougall to find out more about his results and their
implications for runners.
In this study, two groups of six
runners each, trained for 40 days, consisting of four 10-day training phases.
The volume and intensity of training differed between phases. Group 1 ran at
low volume/low intensity during the 1st phase, followed by high volume/low
intensity during the 2nd phase, then low volume/low intensity again during the
3rd phase, and high volume/high intensity during the final phase. Group 2
followed the same protocol, but switched phases 2 and 4.
"Low intensity" meant running at
60-70% of VO2 max, while "high intensity" involved running 1,000 meter reps at
95-100% of VO2 max every other day. "Low volume" represented each runner's
typical training distance, while during the "high volume" phases, the runners
completed twice their normal mileage.
What did the study
MacDougall et al. found reductions
in the ratio of "immune helper" cells to "immune suppressor" cells with
increases in either the volume or intensity of training. Dr. MacDougall
relates, "This ratio is an accepted marker of immune function, and a reduction
indicates an increased susceptibility to infection." The runners' immune
systems were depressed more by increasing the intensity of training than by
increasing the volume.
Dr. MacDougall also found that the
runners' immune systems adapted to the increased training intensity and volume
during the 10 day training phases. This suggests that you may be most at risk
of getting sick following that first hard training session, but that the immune
system adjusts relatively quickly to the increased stress.
How long does it take for your
immune system to recover?
In Dr. MacDougall's study, the
subjects' immune helper/immune suppressor ratios were found to return to normal
by the following day after a workout. This study did not focus on how many
hours it takes for the immune system to recover, but Dr. MacDougall states,
"Other studies have found this ratio to return to normal within 30-90 minutes
There is evidence, however, that
other elements of the immune system may take somewhat longer to recover. In a
recent study conducted by Dr. David Nieman and colleagues at Loma Linda
University, the immune systems of ten experienced marathoners were analyzed
after they ran for 3 hours to exhaustion. This study found alterations in
several types of immune cells during recovery. All of these changes, except for
one, however, returned to normal within 21 hours post-run. These results
suggest that changes to the immune system, even after an extremely strenuous
3-hour run, return to normal in less than a day.
What are the implications for your
The McMaster University results
indicate that you shouldn't suddenly increase the intensity of your training or
your mileage because it can overwhelm your immune system. The subsequent
suppression of your immune system, although short-lived, can open the door to
illness. You should, therefore, take extra precautions when adding speedwork,
races, or extra miles to your running program.
Jason Kajiura, the graduate student
who worked with Dr. MacDougall, and who also coaches runners at the Hamilton
Olympic Club, adds "You are most susceptible to infection at the end of a
workout and for the first couple of hours afterwards, so you really shouldn't
run intervals with a training partner who is sick. Don't go out for a beer
after the workout with him or her either."
What are your chances of getting
An earlier study by Dr. Nieman,
involving 2,000 runners who competed in the Los Angeles marathon, indicates
that our immune systems may indeed be suppressed enough by hard running to
increase the risk of illness. This study found that runners who trained more
than 60 miles per week were twice as likely to get sick in the last 2 months
before the marathon as those who trained 20 miles per week.
This study also compared the rates
of illness during the week after the marathon of individuals who trained for
the marathon but did not run (let's call them wimps) versus those who ran the
marathon. Two percent of the "wimps" got sick during the post-marathon week,
while 13% of those who ran the marathon got sick. It certainly looks as though
high mileage training or running the marathon can increase our chances of
We should be cautious, however, in
reading too much into the findings of these studies. Dr. E. Randy Eichner,
Professor of Medicine at the University of Oklahoma, asserts that psychological
factors often determine the impact of exercise on the immune system. In The
Physician and Sportsmedicine, Dr. Eichner writes, "Whether exercise enhances
immunity or impairs it may, in fact, depend on whether the exercise is a joy or
a stress." A positive attitude towards your running may help keep you healthy.
Whether or not your immune system
will be suppressed enough by a hard run or race to allow you to get sick
depends on the idiosyncracies of your individual immune system, and your
overall stress level. The McMaster University results suggest, however, that
immediately after increasing the intensity or quantity of running is when we
are most at risk.
(This column originally appeared in
Running Times Magazine.)