|
[Exercise
| Aerobic & anaerobic exercise
| Nutrition & exercise]
[Body mass & composition
| Water & electrolyte balance]
[Herb supplementation
| Stimulant herbs | Circulatory
stimulants]
[Joint health | Muscle
soreness | Energy | Protein
| Carbohydrates]
[Carbohydrate loading |
Fat | Oxygen
metabolism | Bone structure]
[Vitamins, minerals & exercise
| Vitamin & mineral supplements]
[Antioxidants | Sports
Anemia | References]
Joint
Health
Weekend
warriors tend to experience sore joints and stiffness after demonstrating
their (whoops our) athletic prowess. Sore knees after running, sore shoulders
after volleyball, sore wrists after a tough game of pacman, all can be
addressed with nutritional supplements that are becoming more popular.
Drink plenty of water while exercising. MSM,
Hyaluronic Acid
and Glucosamine and Chondroitin
all may contribute to healthy joint and connective tissue. They support
the production of cartilage and fortify production of collagen. For real
soreness (you know the difference) see a medical professional.
Muscle
Soreness
Whether
after playing football, volleyball, soccer, or just a good walk at the
mall, who hasn't had sore muscles after a good workout? Drinking plenty
of water allows the body to flush lactic acid from the muscles, reducing
discomfort. A calcium rich diet helps neutralize lactic acid. Herbs such
as Kava Kava and Valerian are beneficial for relaxation of sore muscles
after heavy exercise.
Energy
Several
factors influence the amount of energy an athlete needs. These include
the type, intensity and frequency of training as well as the size, age,
sex and genetic make-up of the person. A middle-aged male marathon runner
has different requirements than a young female gymnast. The main sources
of energy for an athlete are carbohydrates and fats.
In an athletic event,
carbohydrates are the initial fuel source. The energy for short bursts
of activity all comes from carbohydrates. For longer events the energy
comes from both carbohydrates and fats, with the proportions depending
on the intensity of the exercise, pre-event diet and the level of training
of the athlete.
Protein
Adequate,
good quality protein is necessary to preserve lean body mass and maximize
athletic performance. Protein is essential for growth, repair and maintenance
of body tissues. A typical Western diet provides more than enough protein
for athletes and exercisers. Recommended protein intake for adults is
estimated to be 0.8 g protein per kg of body weight per day, although
some experts feel that the needs for athletes may be higher, with endurance
athletes needing up to 1.2 to 1.4 g per kg per day. Athletes who are involved
in very intense strength training or endurance sports may need up to 1.4
to 1.8 g per kg of body weight per day, an amount which can easily be
met by diet. Those who wish to gain weight also have slightly higher protein
requirements. In such cases it may be better to take amino acid supplements
rather than increase intake of flesh foods. Many athletes eat two to three
times the amount of protein they need. This can put stress on the kidneys
and increase the risk of dehydration.
Carbohydrates
Carbohydrate-rich
foods are the best fuel source for athletes. Experts recommend that 55
to 65 per cent of an athlete's calories come from carbohydrates. Most
of this carbohydrate should be in the form of complex carbohydrate, which
is the type found in foods such as whole grain breads, cereals, cooked
dried beans and peas, potatoes and corn. Fruits and vegetables are important
sources of simple carbohydrates.
The body stores limited
amounts of carbohydrates as glycogen. The amount of carbohydrate in the
diet is directly related to glycogen storage and athletic performance.
Daily high intensity training and endurance events deplete body stores
of glycogen and high glycogen stores mean that an athlete can tolerate
repeated training and endurance exercise. Physical training enables athletes
to store more glycogen and use its limited supply sparingly. About 1800
to 2000 calories are available from glycogen stores and this is usually
enough for about 90 minutes of continuous exercise at maximal aerobic
pace.
When an event lasts
more than one hour an athlete may benefit from consuming carbohydrates
during exercise. Drinks, such as diluted fruit juices or sports drinks,
which contain less than 24 g of carbohydrate per cup may be the best form
for this. It is important to eat a high carbohydrate snack after an exercise
session to replace muscle glycogen stores.
Carbohydrate
loading
Adequate
carbohydrate is essential for athletes to replace glycogen stores depleted
by training and competition. This glycogen depletion has led to the practice
of carbohydrate loading, which benefits athletes who are involved in training
or competition for more than 90 minutes. There are several forms of carbohydrate
loading; a common method involves eating a diet that consists of about
60 to 70 per cent carbohydrate about 72 hours before a competition. If
muscles are not damaged, 24 to 36 hours of rest before the event will
allow maximum glycogen storage.
Fat
Fats are
the body's other major energy source. They are twice as dense in calories
as carbohydrates. However, fats cannot be used exclusively as an energy
source and a small amount of carbohydrate must always be available. Aerobic
training increases the ability of the body to use fat as an energy source.
Fat is a major source of fuel for exercising muscles but they only store
a small amount. When this is used up, fat is taken from body stores.
Body fat stores are
more than adequate to provide extra energy and it is not necessary to
get large amounts of fat in the diet. Most athletes eat moderately low
fat diets. Health authorities recommend keeping fat intake below 30 per
cent of total calories as this has been shown to be beneficial in protecting
against various diseases.
Oxygen
metabolism and energy production
Several
nutrients are vital for the efficient burning of fuel with oxygen and
the production of energy. A good diet provides optimal amounts of these
nutrients, which include iron, magnesium and other trace elements.
Bone
structure
A high-density
bone structure is vital for optimal athletic performance and the avoidance
of injuries such as shin splints. Nutrients such as calcium and vitamin
D are vital for healthy bones.
Vitamins,
minerals and exercise
Most nutritional
studies indicate that vitamin and mineral requirements of athletes are
not greater than those of people who don't exercise. Some types of exercise
may lead to losses of certain nutrients but these extra requirements can
often be met by the extra food intake that is necessary to meet energy
requirements.
Vitamin
and Mineral Supplements
Athletes
tend to take nutritional supplements more often than the general population
and some may take very high doses. Many athletes believe that the requirements
for sport are too high or that their diet is too poor to meet their vitamin
and mineral needs. However, most studies also show that blood levels of
vitamins and minerals are similar in athletes and non-athletes, suggesting
that exercise does not deplete body stores. There are a few possible exceptions,
for example, iron in vegetarian athletes.
Many athletes believe
that certain supplements can enhance sports performance. Advertising claims
for such supplements are often impressive but the vast majority of such
supplements are either untested or have failed to show results in the
tests that have been done. Megadoses of vitamins are often used by athletes
to enhance performance. There is little evidence that they do, unless
there are deficiencies. For many athletes, a balanced supplement which
contains vitamins and minerals at the RDA level may be useful as nutritional
insurance. Supplements are not a substitute for a healthy diet.
Due to increased losses
of minerals in sweat and urine, there is a potential increased need for
minerals in athletes. Some studies report that mineral intakes among athletes
are inadequate, especially among those who are attempting to lose weight
for competition. However, most athletes do seem to eat adequate amounts.
It is important to eat minerals in balanced ratios. An excess of one mineral
can have adverse effects on others in the body. An athlete who eats fortified
cereals, sports bars and mineral supplements may be getting excessive
doses of certain minerals.
Antioxidants
[Vitamin
C | Vitamin E | B Vitamins | Thiamin
| Vitamin B6]
[Pantothenic Acid | Calcium
| Chromium | Iron]
High intensity exercise
may cause excess free radicals to be produced in the cells. The damage
from these increases a person's susceptibility to cancer, heart disease,
cataracts, premature aging, decreased immunity and other diseases. (See
page 417 for more information.)
Free radical production
increases as the body's oxygen consumption increases, particularly in
the muscle fibers and in the mitochondria, the energy centers of the
cell. During exercise, the blood is diverted away from organs not actively
involved in the exercise process and then flows back when the exercise
is completed. This reperfusion may also cause the production of free
radicals, a process that can also occur in muscles during exhaustive
exercise. A growing amount of evidence indicates that free radicals
also play an important role in causing skeletal muscle damage and inflammation
after strenuous exercise. The antioxidant vitamins, C, E and beta carotene,
and minerals such as selenium may protect against this free radical
damage, giving protection against disease and, possibly, faster recovery
from damaging exercise.
Strenuous exercise
also leads to a lowering of immune function, putting endurance athletes
at increased risk for upper respiratory tract infections during periods
of heavy training and after events.8 This is likely to be
due to oxidative damage and antioxidant supplements may be useful in
helping to prevent such damage.
Vitamin
C: As an antioxidant vitamin C may help to prevent exercise-induced
oxidative damage. In a 1997 study, researchers examined the effects
of supplements on oxidative stress in athletes. They found that exercise-induced
oxidative stress was highest when those involved in the study did not
supplement with vitamin C.9
Vitamin C supplements
may be beneficial for those who exercise heavily and have problems with
frequent upper respiratory tract infections. Three placebo-controlled
studies have examined the effect of vitamin C supplementation on common
cold occurrence in people under acute physical stress. In one study,
the subjects were school children at a skiing camp in the Swiss Alps,
in another they were military troops training in Northern Canada, and
in the third they were participants in a 90 km running race. In each
of the three studies, the results showed a considerable reduction in
common cold incidence in the group supplemented with vitamin C at levels
of 600 mg to 1000 mg per day.10
Vitamin
E: There is some evidence that vitamin E may decrease muscle fatigue
and improve endurance performance. In a 1998 study, researchers investigated
the effects of high intensity resistance exercise on free radical production.
They also assessed the effects of vitamin E supplementation on free
radical formation or muscle membrane disruption. They divided 12 weight-trained
males into two groups. The supplement group received 804 mg (1200 IU)
once a day for a period of two weeks and the other group received a
placebo. The results showed that high intensity resistance exercise
increased free radical production and that vitamin E supplementation
decreased muscle membrane disruption.11
B
vitamins: B vitamins are essential for the conversion of carbohydrates
to energy, and as calorie and carbohydrate intakes increase, the requirement
for B vitamins also increases. However, this increase will usually be
covered by the increased food intake if nutrient-dense foods such as
whole grain breads and cereals are eaten. There is little evidence that
intake of B vitamin supplements improves athletic performance.
Thiamin:
Thiamin supplements may be helpful in preventing or accelerating recovery
from exercise-induced fatigue. In a study done in 1996, researchers
assessed the effects of 100 mg per day of thiamin in 16 male athletes.
The athletes exercised on bicycles and changes in blood, heart and lung
functioning were measured. In the thiamin supplement group, changes
in blood glucose were suppressed and the athletes felt less fatigued.12
Vitamin
B6: Exercisers and athletes often have low vitamin B6 levels. Exercise
causes pyridoxine blood levels to increase during an exercise session,
possibly because pyridoxine-dependent enzymes are released from muscle
storage or the vitamin is transferred from the liver to the muscles.
There is no evidence that vitamin B6 supplements enhance performance.
Pantothenic
acid: Pantothenic acid is essential for normal adrenal gland function
and the production of cortisone and other adrenal gland hormones. These
hormones play an essential part in the body's reaction to stress. Pantothenic
acid has been reported to improve athletic performance by improving
aerobic capacity and endurance performance, although results of studies
have been mixed.
Calcium:
Female athletes often have menstrual irregularities, which are due to
a disruption of the normal estrogen cycle. Lack of estrogen can lead
to a loss of bone mineral density. If this is combined with a diet low
in calcium, there is an increased risk of developing stress fractures
such as shin splints, weak bones, poor bone healing and eventually osteoporosis.
Calcium supplements in doses of around 1000 to 1500 mg per day may be
beneficial for such women. Increased loss of calcium can also occur
during periods of inactivity.
Recent research
suggests that male athletes who train intensively may also lose enough
calcium from their bones to increase their chances of stress fractures.
In a 1996 study, researchers at the University of Memphis measured the
calcium levels of basketball players and found that after intense exercise
the players lost an average of 422 mg of calcium in sweat during each
session compared with a loss of 40 to 144 mg per day during mild activity.
The researchers also found that over ten months, the players' total
body bone mineral content declined by 6 per cent. When the players received
2 g of calcium supplements the next season, their lean body mass increased
and average bone mineral content increased by 5 per cent.13
Chromium:
Strenuous exercise may increase chromium excretion. Limited research
suggests that chromium supplements, in the form of chromium picolinate
may cause weight loss, reduce fat and increase muscle mass. Because
of these reports, chromium picolinate supplements have become very popular,
particularly among athletes. Most of the research into performance-enhancing
effects has been conducted by manufacturers of supplements and there
is very little independent research to corroborate the findings.
Iron:
Heavy exercise may lead to iron deficiency. Distance runners are at
particular risk, as running appears to lead to a decrease in body stores
of iron. Symptoms of iron deficiency in athletes include reduction in
exercise time, increased heart rate, decreased oxygen consumption and
increased blood lactic acid. A deficiency may result from increased
metabolic requirements, increased red blood cell breakdown and increased
iron losses in sweat. However, unless a person is iron-deficient, supplements
do not appear to improve athletic performance.
Athletes at risk
of iron deficiency include menstruating females; adolescent males whose
iron requirements are high due to growth needs; vegetarians who do not
eat red meat (the richest source of easily absorbed heme iron); and
endurance athletes who may lose a greater amount than usual through
blood losses or sweat.
Sports
anemia
[Magnesium | Zinc]
Sports anemia is
often used to describe a low hemoglobin condition that is relatively
common at the beginning of training. After adaptation, the anemia seems
to subside. It may be due to inadequate dietary intake of iron or the
use of protein for tasks other than red blood cell production during
the early training stages. Iron intake of athletes needs to be carefully
monitored.
Some experts believe
that there is a possibility that exercise may have beneficial effects
in reducing the risk of heart disease and cancer by lowering body stores
of iron which can cause oxidative damage. (See page 257 for more information.)
Magnesium:
Strenuous exercise alters magnesium concentrations in muscle and
blood. Endurance exercise is particularly likely to do this as higher
levels of hormones such as adrenaline and noradrenaline increase urinary
loss of magnesium. Stressful conditions such as intense training and
competition may also increase the need for magnesium.
In a 1998 study,
researchers from the University of Texas examined body magnesium concentrations
in 26 marathon runners during an endurance run. They found that levels
in the muscles and urine dropped significantly, possibly putting the
athletes at risk of decreased performance and muscle cramps.14
Athletes on calorie restricted diets may be at particular risk of magnesium
deficiency and amounts higher than the RDA may be necessary for those
who exercise intensively, possibly in doses as high as 6 mg per kg of
body weight. Supplements may help to increase bone mineral density in
women athletes who have menstrual irregularities and are at risk of
osteoporosis. They may also improve muscle strength in athletes.
Magnesium deficiency
decreases energy efficiency and research has shown that people who are
deficient in magnesium may use more energy during exercise. In a recent
study, USDA researchers investigated the amount of oxygen needed by
healthy women over 50 to perform a certain amount of low intensity work
on an exercise bicycle. When their dietary magnesium was inadequate
(150 mg daily) they used 10 to 15 per cent more oxygen to perform the
work and their heart rates climbed by about ten beats per minute. The
results suggest that magnesium deficiency is associated with increased
physiological demands to do the same amount of work as when magnesium
is adequate.
Zinc:
Athletes can be deficient in zinc as increased needs and increased sweating
and urinary excretion may lead to greater requirements. Zinc deficiency
can affect energy production, tissue repair and resistance to infection.
References
-
Brekhman II, Dardymov IV. 1969; Lloydia, 32; p. 46
- Brekhman
II, Dardymov IV. 1969; Annual Review of Pharmacology; 9; p419
- Rhee
YH, et al. Panax ginseng extract modulates sleep in unrestrained rats.
Psychopharmacology (Berl) 1990; 101 (4): 486-8.
- Shi
L, et al. Effects of total saponins of Panax notoginseng on increasing
PG12 in carotid artery and decreasing TXA2 in blood platelets; Chung
Kuo Yao Li Hsueh Pao 1990; Jan; 11(1): 29-32.
- Ramachandran
U, et al. New experimental model for the evaluation of adaptogenic products.
Journal of Ethnopharmacology; 1990; Jul; 29(3): 275-281.
- Yuan
WX, et al. Effects of ginseng root saponins on brain monoamines and
serum corticosterone in heat-stressed mice. Chung Kuo Yao Li Hsueh Pao
1989 Nov; 10(6): 492-6.
- Ylikoski
T; Piirainen J; Hanninen O; Penttinen J. The effect of coenzyme Q10
on the exercise performance of cross-country skiers. Mol Aspects Med,
1997, 18 Suppl:, S283-90.
- Nieman
DC. Immune response to heavy exertion. J Appl Physiol, 1997 May, 82:5,
1385-94
- Alessio
HM; Goldfarb AH; Cao G Exercise-induced oxidative stress before and
after vitamin C supplementation. Int J Sport Nutr, 1997 Mar, 7:1, 1-9
- Hemilä
H Vitamin C and common cold incidence: a review of studies with subjects
under heavy physical stress. Int J Sports Med, 1996 Jul, 17:5, 379-83
- McBride
JM; Kraemer WJ; Triplett McBride T; Sebastianelli W Effect of resistance
exercise on free radical production. Med Sci Sports Exerc, 1998 Jan,
30:1, 67-72
- Suzuki
M; Itokawa Y Effects of thiamine supplementation on exercise-induced
fatigue. Metab Brain Dis, 1996 Mar, 11:1, 95-106
- Klesges
RC; Ward KD; Shelton ML; Applegate WB; Cantler ED; Palmieri GM; Harmon
K; Davis J. Changes in bone mineral content in male athletes. Mechanisms
of action and intervention effects. JAMA, 1996 Jul, 276:3, 226-30
- J
Am Coll Nutr 1998,17:124-27
Herb Portion of this
essay By Rob McCaleb Herb Research Foundation, Article is reproduced with
exclusive permission from the Herb Research Foundation.
Vitamin portion of
this essay Copyright 1998 Bookman Press. Reprinted from Vitamins, etc.
by Nicola Revley with permission of Bookman Publishing www.bookman.com.au/vitamins/
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