Surely many times you have heard that if you consume carbohydrates (HC) while you train you will burn less fat and most of the positive effects of training will go to waste.
It is not so simple... The reason for
consuming carbohydrates during training is to produce muscle and liver glycogen
savings, while preserving both, we will have the capacity to perform more
during a longer time. It is clear that resistance or "endurance" is
essential since energy consumption and duration is much greater, but, and in
training with loads?
The efforts that are
made during training with loads are much shorter and more intense, with energy
substrates being different to produce ATP. Phosphocreatine is able to supply
energy for muscle contraction for 2-4 seconds, so if we work in maximum
strength ranges, this will be the predominant system along with glycogen, since
this is necessary to resynthesize phosphocreatine.
Training with weights
with a moderate volume, for example, a fullbody workout (3-5 exercises)
produces a depletion of 24-40% in muscle glycogen levels. Obviously this will
depend on the total volume and intensity of the training. In a study conducted
by Tesch et al. in 1986 measurements were made by biopsy of glycogen levels
before and after a lower train training, glycogen decreased by 30%.
More are not always better
Reduced glycogen levels can decrease isokinetic strength as well as isoinercial force. In addition, in this last study, greater strength differences were found in multi-joint exercises such as the squat, with no differences in other monoarticular exercises such as leg extension. According to these works, starting strength training with muscle glycogen low minimums may not be a good idea.
However, in other studies such as that of
Sawyer JC et al. in 2013 no differences were found in the 1RM bench press and
rear squat with high or reduced levels of glycogen
In this last study, the
diet contained more than 30% protein and the adaptation period was longer than
in other studies. Together with a less aggressive depletion protocol, this may
be the reason why such disparate results were found.
Will the HC improve our strength before training?
It depends, some
research shows improvements in performance. However, others like Kulik et al.
(2008) did not find differences. In the latter, the subjects consumed 0.3 g /
kg of carbohydrates immediately before the test, in which the total work and
the number of repetitions were measured, as well as the load used in series of
5 repetitions with the 85 % of the 1RM in a squat.
Haff GG et al. (2000)
examined how isokinetic strength in leg exercises affected the consumption of 1
g / kg (85.7 +/- 3.5 kg) before training and 0.5 g / kg every ten minutes
during training.
Both tests
(carbohydrates vs. placebo) lasting 39 minutes and consisting of 3 leg
exercises were performed by the same subjects separated by seven days. No
significant differences were found in isokinetic strength, only a glycogen
saving was produced in the group that consumed carbohydrates.
It is difficult to find
a determining result that can be applied universally throughout the world,
since the results will depend on the following factors:
- · Previous glycogen levels.
- · Composition of the diet.
- · Training level.
- · Gender (oxidative metabolism).
- · Women consume more fatty acids during exercise.
- · Training volume.
What if we consume them during training?
The purpose of
ingesting carbohydrates during training is the same as ingesting them before,
preventing glycogen levels from depleting, thus decreasing performance.
In works like David M. Laurenson and Danielle Jane Dubé
in 2015, for me some of the best, the effect of consuming carbohydrates during
training is evaluated along with protein in a ratio (3: 1), 36 g of carbohydrates
and 12 gr of protein.
The training consisted
of 3 circuits of squat and press bench with a total of 12 series, decreasing
the number of repetitions in each. After finishing the circuits were measured
the maximum repetitions that were able to do bench press and squat with 60% of
1RM as well as the maximum power generated.
In addition, the
respiratory quotient (RER) was measured on 7 occasions, before, during and
after.
There were no
significant differences in the RER between the group that consumed
carbohydrates and protein and the one that consumed a placebo. The RER is a
measure that shows the relationship between the CO2 produced and the O2
consumed and therefore the oxidative capacity of the muscle tissue. When RER
decreases, (<1) oxidative activity predominates, whereas when RER increases,
(> 1) glycolytic activity predominates.
From all this, it can
be inferred that consuming carbohydrates during a load training does not
diminish the lipolysis nor the oxidation of fatty acids.
Why does not the oxidation of fatty acids decrease?
In order for muscle
contraction to occur, ATP is necessary. Each energy substrate is able to
produce a certain capacity of ATP in a certain time, for example,
phosphocreatine is able to resynthesize ATP very quickly, however, it is only
able to do so for 2-4 seconds. At the other extreme we find β-oxidation, which is
able to resynthesize ATP for a long time, but at a very slow rate (50-65% VO2
max).
Between both ends we
find other metabolic pathways such as anaerobic glycolytic and oxidative
glycolytic. To understand how they contribute to the production of energy, we
must be clear that none works at 100% or 0%. All work in unison overlapping to
a greater or lesser extent.
Returning to the
previous study, you can see how the plasma glucose during exercise is similar
or even lower (take into account the insulinogenic capacity of the amino acids
+ CA2 + dependent transport) in the group that consumed carbohydrates and the
one that consumed placebo. Together with similar measurements in the RER, this
shows that glucose has been used in equal proportion in both groups for the
production of ATP.
For more solidity,
recent work has shown that the consumption of carbohydrates during training at
relatively low intensities 65% VO2 max does not alter the activity of AMPK [9].
It is true that the increase in insulin during training can decrease the release
of epinephrine and myokines, thus reducing lipolysis.
I honestly think that
the intensity of the exercise must be very low for this interaction to occur.
It should be noted that the mobilization of fatty acids from the adipose tissue
is only part of the story, since without the correct mitochondrial function
dependent on (PGC1; PPAR-alpha) and in turn dependent on AMPK, the ability of
lipolysis does not matter , in fact, it can even be harmful as it happens in
the case of diabetics (lipotoxicity).
Regarding performance
parameters, there were no significant differences in power between both groups,
both in the squat and in the bench press. However, the group that consumed carbohydrates was able to perform more repetitions in the bench press.
Then, before or during?
In conclusion, we see
that eating carbohydrates during training does not diminish the oxidation of
fatty acids, it does not mean a benefit in strength increase, however if it
allows a greater volume of training due to the saving of muscle glycogen and
the decrease in glucose production hepatic (muscle protection).
Therefore, both
possibilities are valid when the volume of training is very high and the diet
is reduced in carbohydrates <2 g / kg of body weight. Although it must be
emphasized that intra-tennent supplementation has advantages over pre-tenter
supplementation, such as a lower risk of reactive hypoglycaemia and associated
symptoms, as reported in the work of Koivisto VA et al. [10] The consumption of
carbohydrates of high glycemic index 45 minutes before training produces an
insulin secretion, which, in combination with the hypoglycaemic effect of
physical exercise produces a very aggressive drop in blood glucose, which we
know as reactive hypoglycemia.
All this can be solved
by consuming the same type of HC during training obtaining a more stable
insulin response and a better use of them due to Ca2 + dependent transport. Or
using HC complexes one hour before in liquid form as high molecular weight
amylopectins or cyclic dextrins.
So, when will I gain intra-tread HC?
·
Level of medium-advanced training.
·
In diets with a carbohydrate amount less than 2 gr per
kilo of body weight.
·
High volume of training. A lot of training frequency
with moderate volume.
·
Men will get more benefits than women.
Essential to
individualize amount and type of carbohydrate depending on the duration of
exercise [11]: 60 gr of carbohydrates per hour of training, important to
include several types of HC such as glucose / polymers and fructose. This will
achieve greater oxidation of exogenous HC and glycogen savings. If you have
intestinal problems during exercise when consuming carbohydrates may be due to
the limitation of transport of them. And accumulation in the intestinal lumen
increasing the concentration of water in it. Dehydration can also negatively
affect Na + transport.
