Rehydration
Regular ingestion of
fluids has been proven to be essential for performance. Our body is made up
largely of water (about 60%). Ingestion of fluids during exercise has also been
proved to be beneficial to the body. Large amounts of fluid may be lost during
moderate-severe intensity exercises and in hot or humid conditions in
individuals who engage in regular exercise. Restoration of fluid balance after
exercise is therefore an important part of the recovery process and becomes
even more important in hot, humid conditions. If a second bout of exercise has
to be performed after a relatively short interval, the rate of rehydration is
of crucial importance. Rehydration after exercise requires not only replacement
of volume losses, but also replacement of the electrolytes, mainly sodium which
is lost in the sweat.
Daily sweat and
sodium losses vary widely among individuals and depend on many factors,
including the environment, diet, physical fitness levels and heat
acclimatization status. However, when sweat losses are large, the total sodium
loss will generally be high. It is impossible to prescribe a general fluid
replacement plan to everyone. Athletes and persons involved in regular
exercises should therefore weigh themselves before and after exercise and
replace the weight lost with water. Each kilogram of weight lost is equivalent
to approximately 1 litre of fluid. For example, a person who finishes an
exercise session 1 kg lighter and had consumed 1 litre of fluid during the
session has a total fluid loss of 2 litres. Hence, an additional 1 litre of fluid
should be consumed after the exercise.
The
replacement of sweat losses with plain water will however lead to hemodilution
(making the blood less concentrated). The fall in plasma osmolality and sodium
concentration that occurs reduces the drive to drink and stimulates urine
output, and has potentially more serious consequences such as hyponatremia.
Hyponatremia is a major
problem in ultra-endurance events. Ultra-endurance events tend to test your
endurance to the limit. Examples include running more than 41.6km and cycling
more than 160km.
Drinks intended for
rehydration should therefore have higher electrolyte content (slightly
hypertonic) than drinks formulated for consumption during exercise which should
be isotonic. Fluid intake during exercise depends on the individual and
intensity of the exercise. Some experts have advocated for ingesting between
200-300mls every 15 minutes of working out. But I believe tolerance should vary
according to the
intensity of your exercise.
Protein
replacement
Intense exercise
results in breakdown of muscle tissue. Therefore intake of protein in recovery
meals is recommended to enhance net protein balance, tissue repair and
adaptations involving synthesis of new proteins.
The co-ingestion of
protein with carbohydrate will increase the efficiency of muscle glycogen
storage (the stored format of carbohydrates). Hence, this is also strongly
recommended.
In females who
participate in regular moderate to severe intensity exercises, it is advised
that protein consumption be between 66-94 grams/day, while 84-119 grams/day is
recommended for males. However, for endurance athletes protein requirement is
1.2-1.4 grams/kg body weight/day (source: American College of Sports Medicine).
Carbohydrate
replacement
Individuals who
regularly exercise should aim to achieve a carbohydrate intake to meet the fuel
requirements of their training/exercise program (1 gram of carbohydrate
produces 4 kilocalories) and to optimize restoration of muscle glycogen stores
between work-outs.
General
recommendations are available, but this should be fine-tuned with individual
consideration of total energy needs, specific training needs and feedback from
training performance.
Below is a guideline
for carbohydrate intake for athletes:
– Immediate recovery
after exercise (0–4 hours): 1.0–1.2 g/kg (body weight)/hour consumed at
frequent intervals
– Daily recovery for
moderate duration/low intensity physical activity: 5–7 g/kg (body
weight)/day
– Daily recovery for
moderate-to-severe intensity physical activity: 7–12 g/kg (body
weight)/day
– Daily recovery for
extreme exercise program (4–6 hours per day): 10–12+ g/kg (body weight)/day
- It is valuable to
choose nutrient-rich carbohydrate foods and to add other foods to recovery
meals and snacks to provide a good source of protein and other nutrients. These
nutrients may assist in other recovery processes and, in the case of protein, may
promote additional glycogen recovery when carbohydrate intake is suboptimal or
when frequent snacking is not possible.
- During longer
recovery periods (>24 hours), the athlete should organize the pattern and
timing of carbohydrate rich meals and snacks according to what is practical and
comfortable for the individual situation. There is no difference in glycogen
synthesis when liquid or solid forms of carbohydrate are consumed.
- Carbohydrate-rich
foods with a moderate-to-high glycemic index (bread, cereals, potatoes etc)
provide a readily available source of carbohydrate for muscle glycogen
synthesis and should be the major carbohydrate choices in recovery meals.
Finally, to all
alcohol enthusiasts’ consumption of excessive amounts of alcohol during the
recovery period is not advisable since it is likely to interfere with your
ability and interest to follow guidelines for post-exercise eating.
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