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Endorphins and Exercise
Endorphins and Exercise
Edited abstracts of some recent published scientific articles.
1. Acute mood changes occur with various forms of physical activity.
Increased levels of endogenous opioids (endorphins) in response to
exercise may mediate activity-induced shifts in mood state. Aerobics
class participants aged 20-46 years received the opiate receptor
antagonist naltrexone (which would block the effect of endorphins)
and a placebo in randomized, double-blind crossover fashion on two
separate occasions at the same 75-min high-intensity aerobics class.
Mood states were assessed before and after each class, which were
spaced 5 days apart. Significant differences were observed in
overall mood; with the placebo, mood states became calmer, more
relaxed and pleasant, tending away from depression, anger and
confusion. Positive mood shifts did not occur when subjects were
preloaded with naltrexone, suggesting that activity-generated mood
changes are mediated through endorphinergic mechanisms. (Daniel,
2. In this paper we discuss recent experimental and clinical findings
which lead us to propose that prolonged rhythmic exercise can
activate central opioid systems by triggering increased discharge
from mechanosensitive afferent nerve fibers (Group III or A-delta)
arising from contracting skeletal muscle.
We review evidence that supports the concept that many of the
cardiovascular, analgesic, and behavioral effects of exercise are
mediated by this mechanism and that the same or similar mechanisms
are responsible for the central and peripheral effects of
acupuncture. [Or lying on a bed of nails, etc...<g>]
Based on this hypothesis, and supporting evidence from human and
animal studies, we suggest a mechanism and a potential therapeutic
role for exercise in the treatment of selected patients with
disorders as diverse as hypertension, addiction, depression, and
anorexia nervosa. (Thoren, 1990)
Aerobic (how hard, how long?) or Anerobic?
3. Exercise-induced increases in the peripheral beta-endorphin
concentration are mainly associated both with changes in pain
perception and mood state and are possibly of importance in
A more precise understanding of opioid function during exercise can
be achieved by investigating the changes in beta-endorphin
concentrations dependent upon intensity and duration of physical
exercise and in comparison to other stress hormones.
Published studies reveal that incremental graded and short term
anaerobic exercise lead to an increase in beta-endorphin levels, the
extent correlating with the lactate concentration. During
incremental graded exercise beta-endorphin levels increase when the
anaerobic threshold has been exceeded or at the point of an
overproportionate increase in lactate.
In endurance exercise performed at a steady-state between lactate
production and elimination, blood beta-endorphin levels do not
increase until exercise duration exceeds approximately 1 hour, with
the increase being exponential thereafter. beta-Endorphin and ACTH
are secreted simultaneously during exercise, followed by a delayed
release of cortisol.
These results support a possible role of beta-endorphin in changes
of mood state and pain perception during endurance sports. In
predominantly anaerobic exercise the behaviour of beta-endorphin
depends on the degree of metabolic demand, suggesting an influence
of endogenous opioids on anaerobic capacity or acidosis tolerance.
4. Non-specifically trained volunteers (aged about 25 years) performed
exhausting incremental graded exercise and 1-min anaerobic cycle
ergometer exercise at 2-h intervals to investigate beta-endorphin
behaviour dependent on exercise intensity and anaerobic metabolism.
Venous blood samples were collected prior and subsequent to exercise
until 20 min of the recovery period, as well as in the graded
exercise before and after exceeding the individual anaerobic
Lactate concentration, heart rate and perceived degree of exertion
were also determined. Both types of exercise led to significant
increases in beta-endorphin with levels of endorphin approximately
twice as high after graded exercise as the anaerobic test. In both
tests, there was a relationship between the maximum concentrations
of beta-endorphin and lactate. We therefore conclude that physical
exercise with increasing or mostly anaerobic components leads to an
increase in beta-endorphin, the extent correlating with the degree
of lactate concentration. (Schwarz, 1990)
5. A small treatment group of previously sedentary, psychologically
normal, and medically healthy middle-aged men trained for 4 months
in a structured fitness program. The treatment group was compared
with two age-matched groups: a jogger group and a sedentary group.
Venous blood was collected in the early morning after the subjects
had been fasting for at least 12 h. Resting plasma beta endorphin
decreased following the 4 months of exercise training in the
treatment group. The jogger and sedentary groups demonstrated no
changes following the 4 months.
Aerobic fitness, measured by the maximal oxygen uptake (VO2max),
increased from 36 to 45 ml.kg-1.min-1 in the treatment group after
the 4 months of training. There were no changes in VO2max for either
the jogger group or the sedentary group following the 4 months.
6. Relationship between the intensity of running exercise on a
treadmill and the changes in the concentrations of beta-endorphin
were studied in 10 experienced male endurance athletes. At random
order, the subjects run on a treadmill six exercises which required
on an average 50, 58, 69, 80, 92 and 98% of their maximal oxygen
Plasma levels of beta-endorphin did not show any significant changes
during the 50-80%-tests. During the 92% test, the mean levels
increased significantly from 3.0 to 8.0 pmol/l, and during the 98%
test, from 3.7 to 20.4 pmol/l. Increases in the plasma levels of
beta-endorphin were always accompanied by an increase in the blood
We conclude that intensive running with an anaerobic response causes
an increase in the concentrations of beta-endorphin and ACTH in
plasma in endurance athletes, whereas slight aerobic exercise did
not elicit any response. (Rahkila, 1988)
7. During the past several years, excessive stress has come to be
recognized as a threat not only to quality but also to length of
life. There is increasing evidence that the emotionally distressed
individual may have an increased susceptibility to a number of
Physical activity, in the form of aerobic exercise, is a very
fruitful means for coping with stress. The popular forms of aerobic
activities that are most often pursued in order to help general
cardiovascular condition may, in effect, improve the mental health
of the individual. There are no guarantees that if you follow these
recommendations you will live longer. However, the life you live
will be healthier, happier, more productive, and less stressful.
8. Beta-endorphin and ACTH were determined in the peripheral blood of
14 human volunteers exercising on a bicycle ergometer. After 1 h of
submaximal work below anaerobic threshold (AT), beta-endorphin and
ACTH levels did not change from control conditions.
Eleven of the same 14 subjects performed an uninterrupted graded
exercise test on the same bicycle ergometer until exhaustion. This
time beta-endorphin and ACTH levels increased concomitantly with
exercise of high intensity. The peak values of these hormones were
reached within 10 min after stopping maximal exercise, coincided
with lactic acid peak levels.
A rise in lactic acid levels above the anaerobic threshold always
preceded the exercise-induced rise in beta-endorphin. Within the
population tested, two subgroups could be distinguished: one
comprising individuals whose hormonal response nearly coincided with
the rise in lactic acid (rapid responders) and a second group
composed of subjects whose normal response appeared delayed with
respect to the lactic acid rise (slow responders).
These results support the view that beta-endorphin and ACTH are
secreted in equimolar quantities into the blood circulation in
response to exercise, and suggest that metabolic changes of
anaerobiosis play a key role in the regulation of stress-hormone
release. (de-Meirleir, 1986)
9. The effects of intense exercise on pain perception, mood, and plasma
endocrine levels in man were studied under naloxone (antagonist to
the endorphin receptors) and saline conditions. Twelve long-
distance runners (mean weekly mileage = 41.5) were evaluated on
thermal, ischemic, and cold pressor pain tests and on mood visual
analogue scales (VAS) (simply like a "gas gauge" marked from no-pain
to high pain which you mark to show relative level).
Blood was drawn for determination of plasma levels of beta-
endorphin-like immunoreactivity before and after a 6.3 mile run at
85% of maximal aerobic capacity. Subjects participated on two
occasions in a double-blind procedure counterbalanced for drug
order: on one day they received injections of naloxone following the
run; on the other day, equal volume injections of normal saline.
Ischemic pain reports were significantly reduced post-run on the
saline day, a hypoalgesic effect. Naloxone reversed the post-run
ischemic but not thermal hypoalgesic effects. Joy, euphoria,
cooperation, and conscientiousness VAS ratings were elevated post-
run; naloxone attenuated the elevation of joy and euphoria ratings
The results show that long-distance running produces hypoalgesia and
mood elevation in man. The effects of naloxone implicate endogenous
opioid neural systems as mechanisms of some but not all of the run-
induced alterations in mood and pain perception. (Janal, 1984)
Experimental Model: Specifically--Pain
10. Experimental pain thresholds (electrical intracutaneous finger and
dental pulp stimulation) and plasma hormone levels (beta-endorphin,
cortisol, and catecholamines) were measured in ten healthy sportive
men before, during, and after progressively more strenuous physical
In a double-blind study conducted on two different days, 20 mg of
the opioid-antagonist naloxone or placebo was administered prior to
exercise. A significant pain threshold elevation was found during
exercise. Pain threshold elevation was most pronounced during
maximal exertion, at which time the subjects reported the greatest
subjective fatigue. Thresholds remained elevated 10-15 min after the
end of exercise, and, 60 min after exercise, thresholds returned to
Plasma beta-endorphin increased significantly during exercise.
Plasma beta-endorphin levels did not correlate significantly with
pain thresholds. Naloxone failed to affect pain thresholds,
although beta-endorphin increased significantly more during exercise
after naloxone. <Now that is interesting - if you block the
receptors, wouldn't you expect to get more produced...?>
It is concluded that short-term, exhaustive physical exercise can
evoke a transient elevation in pain thresholds. This exercise-
induced elevation in pain threshold does not, however, appear to be
directly related to plasma endorphin levels. (Droste, 1991)
Cooper-K-H. Gallman-J-S. McDonald-J-L Jr.
Role of aerobic exercise in reduction of stress.
Dent-Clin-North-Am. 1986 Oct. 30(4 Suppl). P S133-42.
Daniel-M. Martin-A-D. Carter-J.
School of Kinesiology, Simon Fraser University, Burnaby, British Columbia,
Opiate receptor blockade by naltrexone and mood state after acute physical
Br-J-Sports-Med. 1992 Jun. 26(2). P 111-5.
de-Meirleir-K. Naaktgeboren-N. Van-Steirteghem-A. Gorus-F. Olbrecht-J.
Academic Hospital, Vrije Universiteit Brussels, Belgium.
Beta-endorphin and ACTH levels in peripheral blood during and after
aerobic and anaerobic exercise.
Eur-J-Appl-Physiol. 1986. 55(1). P 5-8.
Droste-C. Greenlee-M-W. Schreck-M. Roskamm-H.
Benedikt Kreutz Cardiovascular Rehabilitation Center, Bad Krozingen,
Experimental pain thresholds and plasma beta-endorphin levels during
Med-Sci-Sports-Exerc. 1991 Mar. 23(3). P 334-42.
Janal-M-N. Colt-E-W. Clark-W-C. Glusman-M.
New York State Psychiatric Institute, New York.
Pain sensitivity, mood and plasma endocrine levels in man following long-
distance running: effects of naloxone.
Pain. 1984 May. 19(1). P 13-25.
Department of Health Promotion, University of New Mexico, Albuquerque
Decreases in resting plasma beta-endorphin/-lipotropin after endurance
Med-Sci-Sports-Exerc. 1989 Apr. 21(2). P 161-6.
Rahkila-P. Hakala-E. Alen-M. Salminen-K. Laatikainen-T.
Department of Health Sciences, University of Jyvaskyla, Finland.
Beta-endorphin and corticotropin release is dependent on a threshold
intensity of running exercise in male endurance athletes.
Life-Sci. 1988. 43(6). P 551-8.
Department of Sports and Performance Medicine, University of Saarland,
Saarbrucken, Federal Republic of Germany.
Changes in beta-endorphin levels in response to aerobic and anaerobic
exercise. 88 Refs.
Sports-Med. 1992 Jan. 13(1). P 25-36.
Department of Sports and Performance Medicine, University of Saarland,
Federal Republic of Germany.
Beta-endorphin, adrenocorticotropic hormone, cortisol and catecholamines
during aerobic and anaerobic exercise. SO Eur-J-Appl-Physiol. 1990.
61(3-4). P 165-71.
Thoren-P. Floras-J-S. Hoffmann-P. Seals-D-R.
Department of Physiology, University of Goteborg, Sweden.
Endorphins and exercise: physiological mechanisms and clinical
Med-Sci-Sports-Exerc. 1990 Aug. 22(4). P 417-28. 165 Refs
Contributed by Michael Williams, 72301,2647
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