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Part II: Are We Reaching Our Limit? 

By Lauren Evans

In Part I: Are We Reaching Our Limit?, I used an analysis by Dr. Ross Tucker Dr. Jonathan Dugas from The Science of Sport to show that the bar has been set very high with regard to World Record performances. A big reason for this is that many records were set an average of 20 years ago, when doping was the norm. Whether or not these are a fair representation of human limits to performance, the records still stand, and many a top athlete holds onto the ultimate dream of besting them. 

How does an athlete go about breaking a world record? 

In addition to new breakthroughs in research with regard to the importance of periodization, supercompensation, and other training theories, a recent addition to the coaching world is new research on concurrent training. This kind of training integrates aerobic work with resistance training in the same session. Concurrent training basically hits at the core idea of building strength and endurance simultaneously. 

The prevailing perception with coaching has been to build base (endurance) before speed (strength), slow and long before fast and powerful. However, if an athlete could improve both strength and endurance at the same time, it follows that greater and quicker strides will be made in performance. 

This coaching wisdom is based on physiology. When working on endurance, the athlete is physiologically unable to improve strength and vice-versa. One prevents the other; this has been the case for thousands of years. An article in Advanced Fitness Training: A Special Report from Peak Performance (Hamilton & Pye, 2010,) states that it has come down to the molecular level to try to understand how to improve both substrates at the same time. 

Without going too deep into the molecular level, there are two basic enzymes that play a key role during training on muscle growth. These are AMPK (activated protein kinase) and mTORC1 (mammalian “target of rapamycin complex 1”). Endurance training activates AMPK, which, in turn, improves mitochondrial mass of muscles, resulting in greater performance adaptations for endurance.  

mTORC1 is the opposite. It is activated post strength-training and has a direct effect on protein synthesis, resulting in muscle growth. Strength improves based on the extent the enzyme is activated. Strength athletes already realize that increased protein consumption results in greater strength gain (through increasing the chance of protein synthesis in the muscles). Insulin also enhances activation of mTORC1. Thus, by timing intake of amino acids (protein) and insulin (a simple carbohydrate) during strength training, an athlete can maximize muscle protein synthesis. 

So…we have established that the enzyme AMPK improves endurance performance and the enzyme mTORC1 improves strength. What’s the big problem? 

Basically, endurance blocks strength adaptations. AMPK can block activation of mTORC1. This is an obvious evolutionary trait from thousands of years ago that was likely due to the human race adapting to the necessity to search longer distances for food. Thus, increased endurance was essential, while muscle mass only resulted in the need for more calories. Today, when food is thankfully plentiful, we are still stuck in a body that evolved thousands of years ago!

Also, there are some important nuances to consider. First of all, AMPK is activated during exercise but is turned off when we refuel. On the other hand, mTORC1 is turned on after exercise, usually 30 minutes post-exercise and continues to be activated up to an entire day after strength training. (Peak Performance)

All of the above information helps us to come up with a few basic rules for performance enhancement:

1.      Endurance first, strength last.

a.  AMPK activation during endurance will have adequate time to be turned off so that it won’t interfere with the strength session. Working out with weights later in the day / in the evening will allow mTORC1 to stay active throughout rest at night and until it is turned off the next morning during endurance exercise.  

2.      Add intensity to your exercise.

a.  By increasing the stress on your metabolic system (through high-intensity sprints / strides), you can increase activation of AMPK. 

3.      Take fuel to your strength sessions. 

a.  Turn off AMPK with high-carbohydrate foods after endurance. Also, by taking a snack that delivers 6-8g of protein for strength training, you will maximize activation of mTORC1. Finally, by re-fueling with a light snack with protein post strength, you are essentially continuing the effects of the resistance session.  

4.      Keep strength sessions short.

a.  The key in strength exercise is to NOT activate AMPK. Thus, keep strength sessions under 60 seconds in length. This means doing a max of 8 reps. 

Is there proof that these basic rules work? 

 Researchers from California designed two studies using concurrent training techniques on collegiate D1 athletes and formulated their results into comprehensive articles in the Journal of Strength and Conditioning Research in 2008. Their studies measured strength (1 RM Repetition Maximum) of select lower and upper body exercises, muscular endurance, body composition, upper and lower body flexibility, blood pressure and VO2 Max testing. The two groups tested included a “Serial Training Group” and a “Integral (Concurrent) Training Group”. The Serial Training Group performed a traditional workout that included alternating resistance exercises with rest, followed by an aerobic cool-down. The Concurrent Training Group performed the aerobic warm-up first, followed by integrating various resistance exercises with exercises to raise the heart rate of the athletes (for example, short sprints of 30 seconds).  

Before analyzing the results, it is important to remember that, with elite athletic performances, even a small percentage increase in a fitness substrate can mean the difference from a PR or a poor performance. The results are here:

Table 1: percentage change in tests between beginning and end of study




(Courtesy of: Pye & Hamilton, Peak Performance 2010, and JSCR 2008).

Thus, after an 11-week period, the Concurrent Training Group blew the Serial Training Group out of the water! The Concurrent Training Group significantly lowered blood pressure, improved flexibility, improved body composition significantly, and improved in both strength and endurance measurements overall. 

In summary, by safely utilizing concurrent training, athletes will continue to pull out key improvements in performance. World record performances will no longer come ‘at the drop of a hat’, but through research and application at the molecular level along careful planning, nutrition, and training, still more world records will be broken!

1. American Journal Physiology. 1999 276: C120-7.
Bar-Lev, E, “What Type of “Athletic DNA” Do Elite Decathletes Possess?” in Track Coach 195, Spring 2011, pgs. 6225-6228.  
2. European Journal Applied Physiology. 2008 102: 145-52
3. European Journal Applied Physiology. Occupational Physiology. 1980 45: 255-63

4. Journal of Strength and Conditioning Research, 22(5), p1487-1502, (2008)

5. Journal of Strength and Conditioning Research 22(5), p1503-1514 (2008)
6. Pye, J, & Hamilton, A., Advanced Fitness Training for Elite Sports Performance, from Peak Performance. 2010, (pgs. 29 – 48).

7. Tucker, R & Dugas, J, The Science of Sport: World Record Limits? 28 November 2010.

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