Science Summary: The Physiology of Exercise (Cardio or Weights Part 4)

This post is a continuation on my series through Alex Hutchinson’s Which Comes First, Cardio or Weights? All of the following questions are taken from this book and the answers are paraphrased from the authors words with my interpretations and thoughts added in.

— Scott

What role does my brain play in fatigue?

Short Answer:  The central fatigue model (your brain controlling fatigue) is a relatively modern trend that has a lot of backing.  Your brain adapts from the very beginning of an exercise to limit your output.

Long Answer:  When exercising we feel peripheral fatigue (fatigue in the muscles, increased core temp, symptoms of the big picture).  South African researcher Tim Noakes proposed a theory, the central governor theory, in which there is central control of fatigue where the body regulates exertion levels in order to prevent total exhaustive failure.  Research since this proposal has demonstrated support for this theory.  A common example that supports the central governor theory is the finishing sprint we see in nearly every athlete.  As the end draws near, the athlete is able to draw upon energy reserves they had been previously unable to access.  Another study in support of this theory found bikers have significantly lower maximal outputs in hot conditions than in cold conditions.  This suggests there is a central control limiting them in harsher conditions.

Does lactic acid cause muscle fatigue?

Short Answer: No. There are other causes, but lactic acid is not one of them.

Long Answer:  While lactic acid and lactate do play roles in energy consumption, they are not responsible for fatigue and post-workout soreness as lactate levels drop within hours of exercise ending.  As for the fatigue you feel during and after a workout, there is no conclusive research on specific causes, but it is likely that there are several sources that play a part.

Why do I get sore a day or two after hard exercise?

Short answer: It’s the repair cycle your body goes through after exercise.  There is an increase in nerve function ~12 hours after exercise that amplifies discomfort.

Long Answer:  Delayed Onset Muscles Soreness (DOMS) is a common condition that has been studied for a while.  Research has found it isn’t caused by lactic acid of persistent muscle spasm.  The current belief is that it is caused by the tears in the muscle following excessive use.  In a study done by Swedish researchers, it was found that eccentric movements were most likely to cause DOMS as they applied impact at full muscle extension creating the most muscle damage.  This damage-repair cycle rebuilds muscles stronger than before but the repair phase can be associated with soreness.

What is VO2 Max and should I have mine tested?

Short Answer: VO2 Max can be used to calculate fitness but isn’t necessary by any means.  Personal records serve the same function.

Long Answer:  VO2 Max is a measure of the maximum rate at which your body can process oxygen.  As your body adapts to exercise, VO2 Max increases.  VO2 Max testing offers an analytic way to track your fitness but is often redundant to personal exercise experience.

What is lactate threshold and should I have mine tested?

Short Answer:  Lactate threshold calculates the rate at which you body can convert oxygen to energy.  It is a more accurate way of calculating fitness than the VO2 Max test.

Long Answer:  When your body uses energy in an oxygen deprived state, it creates lactate.  Scientists can monitor lactate levels in your body to determine the degree of intensity your body can sustain indefinitely via the point at which lactate levels begin to rise.  This test is useful for endurance athletes who need to be concerned about stable performance of long periods of time.

How can I avoid muscle cramps?

Short Answer: There is no definitive research for or against home remedies such as pickle juice and bananas though there is a lot of anecdotal evidence.  There is scientific support for reducing intensity, increasing rest, and progressing in a realistic fashion in stead of over training.

Long Answer:  It is commonly thought that cramps are due to electrolyte imbalances, specifically sodium and potassium, but modern research has been unable to conclude this.  Studies comparing cramp prone athletes against their cramp free counterparts found no significant difference in electrolyte levels or electrolyte consumption.  Though the source is not entirely understood, there are some research backed cures for dealing with cramps.  The best is simply stretching the affected muscle which will cause the muscle fibers to relax.  A 2010 study done at Brigham Young University found that subjects experiencing cramps recovered about 45% faster when they consumed a 1/4 cup of pickle juice following the cramp.  Ultimately, cramps are still a relatively grey area from a scientific standpoint and you may be best off just finding what works for you.

What’s happening when I get a stitch?

Short Answer:  It isn’t your diaphragm, your ligaments, or your lungs.  It’s actually most likely a irritation in the abdominal lining caused by friction due to movement.

Long Answer:  Researcher aren’t sure about the specific cause of stitch symptoms, but they have ruled out many commonly attributed factors such as diaphragm exhaustion or ligament strain.  Australian researcher Darren Morton found that stitch symptoms could be replicated by applying stimulus to areas of the upper (thoracic) spine which suggests a nerve component.  Another study conducted in 2010 found an association between spine curvature and intensity of stitch symptoms.  Current thoughts are that stitches are caused by irritation in the lining of the abdominal cavity as it rubs against areas such as the rib cage or spine during movement.  Along this line of thought, doctors recommend exercising with an empty stomach and practicing better back posture to reduce factors contributing to this irritation.

At what time of day am I strongest and fastest?

Short Answer:  Around 6 p.m. unless you’re accustomed to training at another time in which case it would be the time you normally exercise at.

Long Answer:  French and Tunisian researchers found that study participants had a maximum power output near 6 p.m. and a low point at 6 a.m.  This maximum output in the evening was about 10% greater than the minimum output in the morning.  Other studies may suggest this has to do with core body temperature as researchers in Guadeloupe (an island just north of South America) found no variation in maximum output in morning or evening.  The researchers in this study suggested the warm environment acted as a passive warm up for the participants.  Despite all this, your body will acclimate to the schedule you put it on.  Morning workouts will increase you body’s functionality in the morning.

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