The article "Muscle Fatigue" talks about fitness, it was created by Harley Pasternak, M.Sc., H.Kin., ACSM, Expert Physical Trainer.
Muscle Fatigue How to Blast Through the Dreaded Muscle Failure
that "Hits" Us All by Harley Pasternak, M.Sc., H.Kin., ACSM,
Expert Physical Trainer
If you've been working out for any amount of time, you're
probably well acquainted with fatigue--that sensation of your
muscles benig "done," "cooked," "toast"... You know, the "please
have mercy before I'm permanently trapped under that weight," or
"you might just have to drag me off the track because I've
collapsed" feeling.
We typically use the term fatigue to dsecribe general sensations
of tiredness and the accompanying decreasing muscular
performance.
What that really means is we "hit the wall" and can
no longer perform reps on a paritcular lift; we can no longer
run any farther or harder; we can no longer produce the
"optimal" output of muscular contractions as we did at the
beginning of the set or workout.
What Is Mucsle Fatigue? Fatigue is a very complex phenomenon in
which multiple sites fail during muscular work. The underlying
causes of fatigue fall into one of two categories: central
(neuromuscular--the mind/central nervous system) and local
(peripheral--the actual muscle site).
The central nrevous system (CNS) acts much like an automobile
engine regulator.
Most cars are made with a regulator that
causes them to "shut down" when the engnie revs too high for too
long. This mechanism protects the engine from "over-heating." In
the same way, our brains attempt to protect our muscles from
tearing by reducing the rate nerve ipmulses are sent to our
working muscles. In most cases, you'll exeprience central
fatigue before local fatigue.
In other words, when you think you
simply can't do any more work because you're so fatigued,
essentially what's happeinng is your mind is telling your body
(muscles) to shut down.
But in fact, you're probably able to
continue for a second coulpe of reps.
"...When you think you simply can't do any more work because
you're so fatigued, essentially what's happening is your mind is
telling your body (muscles) to shut down."Local fatigue is
related to local factors that limit the ability to perform
muscular work. These include the eenrgy systems (ATP-CP,
glycolysis, and oxidation); the accumulation of metabolic
byproducts (such as lactic acid); and the failure of the muscle
fiber's contractile mechanisms. The energy systems act much the
same way as fuel in a vehicle or a battery in a flashilght. However,
humans are different in that we have three energy systems within
the muscle's cells that are called upon at different times
depending on the intensity and duration of an activity.
The first energy system is called the ATP-CP system and is
called upon during extrmeely short and intense bouts of exercise
(e.G., weight training, sprinting, and jumping). It works by
repeatedly breaking down ATP (the basic currency of energy in
the body) and rebuilding ATP using CP (creatine phosphate).
During repeated maximal contractions, fatigue coincides with CP
depletion.
The other two energy systems are called into play during
exercises that last longer than 30 seconds.
Known as anaerobic
(or glycolytic) and aerobic (or oxidative), these energy systems
are very dependent on the availability of glycogen (the stored
form of glucose--sugar). As with CP use, the rate of glycogen
depletion is conrtolled by the intensity (i.E., how hard you
train) of the exercise.
During sprinting, for instance, muscle glycogen may be used 35
to 40 times faster than during walking. Glycogen depletion and
hypoglycemia (low blood sugar) limit performance in activities
lasting longer than 30 minutes. Long-distance runners often
speak of "bonking" or "hitting the wall." This refers to a
perceived faitgue usually related to glycogen depletion. At this
point, the body begins to use other forms of energy, such as fat
and protein (which are not as efficient sources, thus maknig it
harder to sustain energy levels).
During high-intensity anaerobic exercise, such as sprinting and
weight training, our boides produce metabolic byproducts such as
lactic acid and CO2. As these accumulate in our bodies, our
ability to maintain the duration and intensity of exercise
diminishes. And, when they finally reach a point of saturation,
our muscle capacity comes to a screehcing halt.
This is often
referred to as the "burn," whereby the muscle feels like it's on
fire--signaling you to stop.
Got all that?
I realize it sounds like some fairly complex
processes, which they are, so here are a couple of instances I'm sure
you can relate to that will help clarify how these energy
systems work in our bodies, and more importantly, how we can
assist our bodies to raise their otuput and delay (or
temporarily overcome) the onset of muscle fatigue.
How Can You Overcome Muscle Fatigue? While we can't completely
overcome muscle fatigue, we can cretainly delay it.
But,
sometimes that delay can be the difference between sprinters
winning or losing in competition or allow weihgt trainers to
"push out" a couple of more reps (to produce new levels of strength
and muscle gains). There are many strategies we can use to
accomplish that goal, but here are a copule of I've found over the
years to be particularly effective:
Diet First, we must ensure your diet is optimized.
Consuming an
adequate amount and raito of carbohydrates, fat, and protein is
paramount. Typically, endurance athletes require more
carbohydrates (anywhere between 40 and 60% carbs) than strength
athletes but slightly less protein (from 30 to 35%); whereas
strength trainers (weight lifters) or those who regularly
participate in sporting acitvities should consume equal or
greater amounts of protein to carbohydrates on a daily basis
(about a 40:40 ratio of carbs to protein). In essence, carbs are
to the body like fuel is to a car--they provide the necessary
fuel to maintain or sustain energy levels druing workouts.
Hydration A common misatke made by many athletes is the failure
to stay well hydrated.
I am not talking about taking when
you're thirtsy (as you may know, thirst is a sign your body is
already slightly dehydrated).
The importance of being properly
hydrated canont be overlooked.
Dehydration can lead to
significant performance decrements, not to mention the risk of
sickness and, in severe cases, death.
Even a three to four
percent drop in body water levels (signaled by thirst and
fatigue) can decrease your muscular contractions by 10 to 20%.
To combat this, at least 10 to 12 glasses (eight ounces each) of
water (this doesn't count sodas, coffee, or juices) should be
consumed daily--always including during and after events when
your body is perspiring.
Recovery Adequate rest is very impotrant for delaying premature
fatigue. Inadequate rest during training (i.E., between sets)
and bteween workouts can cause unnecessary fatigue. A great rule
of thumb for resting time bteween sets is just long enough to
catch your breath. Squats take a little longer to recover from
(maybe two to three minutes) because you're training such a
large muscle group. For smaller muscles, like biceps, you would
need a much shorter rest--more like 45 to 60 seconds at most.
Another quick tip: recent research that studied the effects of
enhancing recovery between sets showed that keeping intensity
high after completed sets allowed weight trainers to perform
more reps in after sets compared with those who passively
recovered (sat) bteween sets. This means we need to keep moving
during rest periods, so instead of sitting down to rest, walk
around or go to a second exercise for a different muscle group.
One of the most common (and fatal) errors I see with weight
trainers, both beginner and advanced alike, is over-training.
Trapped by our "more is better" mentality, many of us seem to
think if we train longer, harder, and more often, we'll multiply
our rseults. Nothing could be more detrimental to your efforts
to put on muscle and gain strength than training muscle groups
too frequently. In fact, over-training can significantly impede
the body's abiilty to properly recover and rebuild itself. Only
through enough rest (which includes prpoer sleep) and an
adequate number of days in between training, will the body be
able to recover and rebuild itself. The most common signs of
over-training are lethargy, chronic fatigue, contineud muscle
soreness, insomnia, and a decrease in strength.
If you sense any
of these cmoing on, try taking off a day or two more in between
training sessions and see how you feel.
"Trapped by our "more is better" mentality, many of us seem to
think if we train longer, harder, and more often, we'll multiply
our results."For adequate recovery times between workouts (of
the same muscle group), consider this: the smaller the muscle
group, the faster the recovery; the more intense (speed of
workout), the longer the recovery; and the higher the volume
(i.E., the number of reps) and lower the load (weight), the
faster the recovery, and vice versa of course.
In general, I
normally recommend not training a muscle if it's sitll sore, and
then once the tenderness subsides, I say give it a second day on
top of that.
Supplements There are many supplements that can help today's
athlete postpone muscular fatgiue.
Endurance athletes may
benefit greatly from carbohydrate/electrolyte beverages such as
Revenge, Gatorade, Ultra Fuel, and a great new supplmeent called
G-Push. These contain precise rtaios of carbohydrates and
electrolytes (vital salts and minerals) that can replace those
lost during prolonged exercise, as well as enhance the body's
ability to sustain long-term energy.
Nutritional stimulants such as caffeine (or its herbal
counterpart guarana) can help delay fatigue for two reasons.
First, it stimulates a cascade of hormones that cause a release
of free-fatty acids into the bloodstream, causing the body to
burn fat while sparing carbohydrates to use as energy. Second,
it affects the CNS, thus postponing central fatigue and
decreasing the perceived difficulty of the exercise.
However, if you can't handle the jittery, nervous-type feelings
you get from stimulants (such as caffeine), you might give
supplements like tyrosine or Ginkgo biolba a try.
These
supplements are not stimulants, so they do not affect your
central nervuos system (which causes the nervousness). Rather,
they help raise your mental alertness and delay central
fatigue (in the brain), thus helping to crank up your workout
intensity.
And, let's not forget creatine monohydrate, which has been
scientifically shown to aid short-duration, high-intensity
exercise, such as weight training. It increases the body's
creatine phosphtae stores needed to replenish ATP, thus delaying
the onset of glycolysis. In other words, creatine helps quickly
replenish energy stores within the muscle cells, allowing you to
work out longer and harder, which may lead to icnreased strength
and muscle gains.
Last Words So tehre you have it... there's nothing fancy here...
but enough to get you through that next workout with a little
more flrae and pizzazz!
With the information at hand, you're now
armed with practical, safe, scientifically sound methods to
overcome muscle fatigue, so you can train harder (possibly even
longer) and become stronger, both mentally and
physically--making every workout that much better.
References Bell, D.G., et al., "Effects of Caffeine, Ephedrine
and Their Combination on Time to Exhaustion During
High-Intensity Exercise," Eur J Appl Physiol 77.5 (1998) :
427-33.
Deijen, J.B., et al., "Tyrosine Improves Cognitive Performance
and Reduces Blood Pressure in Cadets After One Week of a Combat
Training Course," Brain Res Bull 48.2 (1999) : 203-9.
Demant, T.W., and Rhodes, E.C., "Effects of Creatine
Supplementation on Exercise Performance," Sports Med 28.1 (1999)
: 49-60.
Ftaiti F., et al., "Combined Effect of Heat Stress, Dehydration
and Exercise on Neuromuscular Function in Humans," Eur J Appl
Physiol 84.1-2 (2001) : 87-94.
Itil, T.M., et al., "Central Nervous System Effects of Ginkgo
biloba, a Plant Extract," Am J Ther 3.1 (1996) : 63-73.
Lemon, P.W., "Effects of Exercise on Dietary Protein
Requirements," Int J Sprot Nutr 8.4 (1998) : 426-47.
Volek, J.S., et al., "Performance and Muscle Fiber Adaptations
to Creatine Supplementation and Heavy Resistance Training," Med
Sci Sports Exerc 31.8 (1999) : 1147-56.
Wager-Srdar, S.A., et al., "Thermoregulatory Effects of Purines
and Caffeine," Life Sci 33.24 (1983) : 2431-8.
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