Category Archives: workout

Physiology of Fatigue: What are we fighting when we try to push through a challenging workout?

Why are workouts so hard?

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We are fighting a lot when we push ourselves through workouts that are challenging. There are times we may be fighting a bad attitude, discouragement, lack of confidence, drive or our own personalities, but we are, at times, also fighting a very complex regulatory system designed to protect us from severe self-induced damage.

Fatigue and Temperature

Fatigue can be defined as reaching a point where the body seeks to slow down or stop. Exhaustion is that point where a person (or animal) is unable to continue. The most important factor driving suppression of motor activity is believed to be brain temperature. In an untrained person, exhaustion may occur when core body temperature reaches 100 to 102F(~38 to 39C) while a highly trained person may not reach exhaustion until body temperature has reached 104F (~40C).

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Stiff, Inflexible, Invincible WODMasters shirt for the Masters CrossFit Athlete. And for other people who may also be stiff and inflexible.

Interestingly, it’s not only humans who are stopped at these temperatures. Internal temperatures of ~104 oF will stop other animals whether sprinters (Cheetahs) or the generally more placid and possibly endurance-oriented (Goats) (Taylor and Rowntree 1973). And yes, I’m sure you’re wondering: temperatures were measured rectally, and the animals ran on a treadmill while wearing masks so oxygen and carbon dioxide levels could be assessed. The research team also cranked the heat up. Cheetahs ran for shorter periods when the room was hot. The authors of this paper concluded that the duration of a Cheetah’s sprint is limited by core temperature, which is influenced by air temperature. Keep this in mind when you are working out in the summer with no air-conditioning. There are other factors that are also thought to play roles in regulation of intense physical output. Working muscles send feedback to the brain, and in most of us, they are not yelling “Go! Go! Go!” At first they are saying things like “we need more oxygen over here” and “pump the heart faster.” Unfortunately you maximum output can only go on for as long as you have the necessary materials to keep the system running. Your maximum obtainable heart rate will matter. That may be one you cannot make “just do it.” although you can improve your ability to pump blood with training.

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Strong Woman Shirt with All-Seeing Kettlebell. Awesome Power and exceptional femininity

Blood concentrations of important factors or metabolites, and depletion of working materials, are also monitored by the brain. Changes in concentrations and availability of neurotransmitters, endorphins, cytokines, along with a build-up of ammonia in the brain, occur during continued intense exercise. Cerebral energy use increases requiring more oxygen, while blood flow will decrease by about 20% due to constriction of brain arterioles. Low oxygen, loss of neurotransmitters, and accumulation of waste products can cause a problem that is truly “all in your head” but a real problem none the less. An increased need for oxygen and fuel in the brain may be part of what causes someone to want to slow down or stop.

Another strong woman shirt for strong women.  Be fit and wear an awesome shirt.  For strong women who love art, irony and kettlebells
Another strong woman shirt for strong women. Be fit and wear an awesome shirt. For strong women who love art, irony and kettlebells

Practice improves physiology and performance.

Increasing oxygen intake may improve performance not necessarily by providing muscles with additional oxygen, but in providing the brain with what it needs to keep the system running. Depletion of brain glycogen and excessive use of lactate as an alternative brain fuel may also signal fatigue. This may happen faster in untrained athletes. Physical training is, after all, about much more than simple strength and endurance. It includes getting all systems, including subtler aspects of physiology like the ability to dissipate heat, produce lactate, carry oxygen and oxygenate the brain, to work as efficiently as possible. We can reach our limits, but our brains rarely stupid enough to allow us to go beyond them and recklessly run our bodies off the edge of a cliff. The brain also likes to know what’s going on and practice (going through the motions) and rehearsal are important to performance. Rehearsing movements before a WOD may be as important as traditional warming up. It preps your system for what it is about to do and lets it know what is coming. Even imagining movements may help improve strength output and performance (Jeukendrup et al. 1996).

CrossFit training, rational mental toughness.

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Mona Lisa and Her Kettlebells bring quiet dignity to the toughest workout.

We can improve performance intelligently rather than fight what we imagine to be a lack of mental toughness, or allow ourselves be discouraged. We can keep cool and well-hydrated. We can be patient enough to recognize that our physiological and biochemical systems are becoming more efficient as we train, even if our speed or strength has plateaued, and not give up on long-term goals. Finally, encouragement and cheers can help people achieve their maximal level of oxygen consumption (Nybo & Secher 2004) and maximum performance. This may be especially true if they are new to Crossfit and have type A personalities. New Crossfitters may be putting superhuman efforts into their workouts and should be congratulated and admired for these as much as our seasoned champions.

Taylor CR, & Rowntree VJ (1973). Temperature regulation and heat balance in running cheetahs: a strategy for sprinters? The American journal of physiology, 224 (4), 848-51 PMID: 4698801

JEUKENDRUP, A., SARIS, W., BROUNS, F., & KESTER, A. (1996). A new validated endurance performance test Medicine & Science in Sports & Exercise, 28 (2), 266-270 DOI: 10.1097/00005768-199602000-00017

Nybo, L., & Secher, N. (2004). Cerebral perturbations provoked by prolonged exercise Progress in Neurobiology, 72 (4), 223-261 DOI: 10.1016/j.pneurobio.2004.03.005

Taylor CR, & Rowntree VJ (1973). Temperature regulation and heat balance in running cheetahs: a strategy for sprinters? The American journal of physiology, 224 (4), 848-51 PMID: 4698801 Nybo, L., & Secher, N. (2004). Cerebral perturbations provoked by prolonged exercise Progress in Neurobiology, 72 (4), 223-261 DOI: 10.1016/j.pneurobio.2004.03.005ResearchBlogging.org

Crossfit High Intensity Interval Workouts

Crossfit – High Intensity Interval Training workouts.

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Two ugly crossfit men talk about crossfit, high intensity interval training workouts and WODMASTERS WORKOUT SHIRTS.  Why aren’t they weraing them now?  Get to the shop guys.

Endurance exercise is recommended for cardiovascular health.  Years of research have found that about 30 minutes of cardio will reduce risk of stroke and heart attack.  It will also improve insulin sensitivity, reduce risk of diabetes and improve memory and brain function.  Until very recently, there has been little research on the benefits of CrossFit type exercise on health.  These studies focus on High Intensity Interval Training.  High Intensity Interval Training workouts consist of multiple sets of intense exercise that last 1-4 minutes.  These are spaced with short rest periods.  Or periods of light exercise.

High Intensity Interval Training Workouts with gas mark.
There are so many ways to make life harder. High Intensity Interval Training Workouts can make you hurt faster

Research on this approach to exercise indicates that this approach may number of ways.  These include cardio and respiratory fitness.  And also insulin sensitivity and arterial stiffness.  Arterial stiffness is an indicator for risk of cardiovascular disease.  It is also looking like High Intensity Interval Training may be better at controlling or preventing high blood pressure than the traditional 30 minutes of sustained cardio.

CrossFit Training vs. Running?

The question of is CrossFit better than running is not known yet.  And CrossFit is different than the types of High Intensity Interval Training being tested.  In a nutshell, CrossFit is a fitness program that involves high intensity exercise.  Many different muscle groups are targeted in a CrossFit workout (also known as a CrossFit WOD.)  Workouts may last 5-20 minutes and involve springs, weight lifting, pull-ups and other bodyweight exercises.  If you are wondering “what is CrossFit” try this link. CrossFit exercises may or may not include periods of rest between sets.  However, there is a lot of shifting of focus.  Intensity may be sustained, but not sustained on the same muscle groups.  This might be better for vascular health.

CrossFit High Intensity Interval Training.

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Stiff, Inflexible, Invincible WODMasters shirt for the Masters CrossFit Athlete. And for other people who may also be stiff and inflexible.

Short periods of high intensity interval training type exercise improve capillary growth.  This allows for greater blood flow to tissues.  Including muscle.   It is possible that intense exercise impacting multiple muscle groups would be better than exercise that impacts only legs (as in running). This is an exciting area of research.  It will be interesting to see what comes up next.  Hopefully more research will be done soon that will look at whether or not CrossFit or High Intensity Interval Training does as well with brain health and control of diabetes.  For a look at recent papers take a look at:

Cocks, M., Shaw, C., Shepherd, S., Fisher, J., Ranasinghe, A., Barker, T., Tipton, K., & Wagenmakers, A. (2012). Sprint interval and endurance training are equally effective in increasing muscle microvascular density and eNOS content in sedentary males The Journal of Physiology, 591 (3), 641-656 DOI: 10.1113/jphysiol.2012.239566

Spence AL, Carter HH, Naylor LH, & Green D (2013). A prospective randomised longitudinal study involving 6-months of endurance or resistance exercise on conduit artery adaptation in humans. The Journal of physiology PMID: 23247114

Caffeine Coffee and Timing for performance and competition

Caffeine Coffee Tea (Coke?).  First we’ll start off talking about the importance of time of day in athletic performance.

Compete, if possible, in the afternoon over the morning.

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CrossFit Seven Athlete waits for his event. He’d look better in a WODMASTERS shirt

Athletes perform better in the afternoon and early evening than in the morning.This is the case for weightlifting as well as for endurance exercise like running, swimming and cycling.  Even penmanship is less precise in the morning.  Possibly it’s a warm up issue.  But it looks like a circadian rhythm issue too.  The circadian rhythm is an internal clock that regulates what you do during a day.  It regulates sleeping patterns.   Also body temperature, hormones and fluid regulation. Muscle response to stimulation is stronger in late afternoon.  A 2012 study (Mora-Rodriguez et al.) looked at electrically-induced response in weight lifters.  And they looked at voluntary contraction too, comparing morning and afternoon response.  All weightlifters were men.  All were described as highly trained elite weightlifters. The weightlifters lived in a research facility and were denied caffeine for 4 days before testing.  (That must have been tough.) The study also compared voluntary and electrically induced response in the morning with and without caffeine.  If you are wondering “what is caffeine” get some coffee.  Lifters were given caffeine on a body weight basis.  Caffeine was taken 60 minutes before performance testing.

Study Details: Caffeine, Weightlifting and Performance.

  • Test times were at 10:00 am and 6:00 PM.  Caffeine intake was 3mg per kg.  (if you weigh 80kg.  that’s about 240 mg or  about one 12 ounce cup of extremely strong starbucks style coffee.)  Caffeine was taken 45 minutes before lifting.
  • Morning performance vs. evening performance
  • Morning performance with Caffeine supplement vs. Placebo.

Results

Mother and daughter at Crossfit Seven in Fort Worth, TX.  Caffeine Coffee?  You bet.
Mother and daughter at Crossfit Seven in Fort Worth, TX. Caffeine Coffee? You bet.

Strength and power output with placebo was better in the evening by 3% to 7.5% over morning strength and power output.   Caffeine in the morning increased strength and power output by 4.6% to 5.7% for squats when compared to no morning caffeine.  Electrically invoked response increased by 14.6% and nerve activation jumped 96.8%.  Squats seemed to be more caffeine dependent than bench press.  Maybe mornings are just meant to be spent drinking coffee.

If you are doing Crossfit Open competitions:

This site started as a site for Crossfit Masters Athletes, so here is the info for Crossfit readers:  For people trying to qualify for regionals or the CrossFit Games 2013 this could be important.  Do your Open CrossFit WOD’s in the afternoon.   If you can.  Caffeine in the morning will get your muscles up to the level they’d be if you did your workout in the afternoon.  So when you are competing during a morning WOD, have some coffee 45 minutes before the event.  And don’t forget the four days of abstinence before hand.Last note: caffeine peaks in your blood stream 30-60 minutes after its taken.

  • Abstain from coffee for 4 days before your event
  • Drink Coffee 30-45 minutes before you start
  • Do your event in the afternoon if possible

Note: Tablet or pure caffeine Coffee may not give the same results:

You can read more about the effects of coffee vs caffeine here.

Mora-Rodríguez R, García Pallarés J, López-Samanes Á, Ortega JF, & Fernández-Elías VE (2012). Caffeine ingestion reverses the circadian rhythm effects on neuromuscular performance in highly resistance-trained men. PloS one, 7 (4) PMID: 22496767