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“We observed that in untrained muscle, resistance exercise stimulated both myofibrillar and muscle mitochondrial protein synthesis. We contend that this is the first study to report an increase of human muscle mitochondrial protein synthesis after acute exercise.” Sarah B. Wilkinson et al J Physiol 586.15 (2008) pp 3701-3717

Resistance Training Builds Muscle—and Mitochondria

The connection between resistance and aerobic training grows stronger with each study. In 1999, the Goreham study found that high-intensity resistance training stimulated metabolic changes characteristic of aerobic training; see our # 322. Seven years later, Tang reported an increase in aerobic potential and significant hypertrophy following resistance training; see our # 323. (Hypertrophy was the missing element in the Goreham study.)  Two years later, in 2008, Wilkinson and colleagues broke new ground with a finding that resistance training increased the formation of mitochondria, the kingpins of aerobic fitness.

“The primary aim of this study was to measure myofibrillar [strength] and mitochondrial protein synthesis after an acute bout of either resistance or endurance exercise, and repeat this after 10 weeks of resistance or endurance exercise training,” Wilkinson and her team wrote in introducing their study. 

To test their hypothesis that a single bout of resistance (or endurance) exercise would stimulate both strength and endurance fibers, Wilkinson et al devised a unique protocol. (They also predicted that continuous training would produce a more exercise-specific response.) The training protocol would not be practical in a gym setting, but it was ideal for the experiment.

Ten healthy untrained men (average age 20.5 years) did resistance exercise (knee extensions) with one leg and endurance exercise (cycling) with the other leg. (A one-leg cycle was specially constructed for the study.) Resistance exercise (RE) and endurance exercise (EE) workouts were done on separate days. Training continued for 10 weeks. The participants were tested at rest, after a single bout of each exercise, and at the end of the 10 week program.  

The participants were their own controls, because one leg was assigned to RE and the other leg to EE. This format had the additional advantage of increasing statistical power by comparing metabolic responses in the same person.

Resistance exercise is characterized by myofibrils, the contractile element of skeletal muscle; endurance exercise, on the other hand, is characterized by mitochondria, the endurance element of skeletal muscle. RE builds myofibrils, and EE builds mitochondria; that is not in dispute. At issue is the connection, the synergy, between the two forms of exercise.

Wilkinson and her colleagues, in effect, put a microscope on the physiological adaptations in order to understand the interplay between the two forms of exercise. Specifically, they measured the rate of myofibrillar and mitochondrial protein formation in response to the two forms of exercise.

“We observed that in untrained muscle, resistance exercise stimulated both myofibrillar and muscle mitochondrial protein synthesis [formation],” Wilkinson et al reported. “We contend that this is the first study to report an increase of human muscle mitochondrial protein synthesis after acute [short, hard] exercise.”

That was the initial response, after the first resistance exercise (RE) workout. “RE stimulated both myofibrillar and mitochondrial protein synthesis, 67% and 69%, respectively,” they reported. Strength and endurance elements responded equally to the first bout of resistance training—as predicted.

As also predicted, the response was more specific after 10 weeks of training. “After training, only myofibrillar protein synthesis increased with RE (36%). Endurance exercise (EE) stimulated mitochondrial protein synthesis in both the untrained, 154%, and trained, 105%, but not myofibrillar protein synthesis.” (Emphasis mine)

In other words, 10 weeks of strength training (knee extensions) stimulated an additional 36% increase in the formation of the contractile fibers. Endurance training (cycling), on the other hand, stimulated a 154% increase of mitochondrial protein formation after the first workout, and 105% after 10 weeks of training. Endurance training, however, stimulated only endurance formation. It did not stimulate growth in the contractile fibers, at any time.

The lack of strength fiber formation in untrained muscle in response to endurance training was not predicted; it was apparently a surprise.

The new finding is that resistance exercise (knee extensions) initially stimulated growth in both the strength and the endurance elements in the thigh, while endurance training stimulated growth in only the endurance elements, in trained and untrained muscle. Endurance training is more specific—and limited—than resistance training.

(For more details—and there are many—consult the full report: Wilkinson et al, J Physiol 586.15 (2008) pp 3701-3717)

*  *  *

Professor Stuart M. Phillips, who was also involved in the Wilkinson study, commented meaningfully in an email on the findings in the three studies we’ve been discussing.

“The perceived divergence and ‘exclusivity’ of response with each form of training – i.e., aerobic training begets mitochondria and resistance training leads to muscle hypertrophy – is, we think, incorrect. The responses lie instead along a continuum and yet you cannot have one without some of the other. It is true enough that when practiced for long periods of time that the phenotype becomes more specialized, but is this due 100% to training or that the training allowed you to express some underlying genetic potential for adaptation? Some people are just born runners and others lifters in my view!”

*  *  *

“Some people are just born runners and others lifters in my view!” So true. Phil Heath, the 2011 Mr. Olympia, would be wasting his time trying to win the Boston Marathon. By the same token, Kenya’s Geoffrey Mutai, who won the 2011 Boston Marathon in record time, would be out of place on stage at the Olympia; he would be equally hopeless in the “World’s Strongest Man” competition.

In truth, most of us would be out of place in either venue.

While my phenotype is less clear, I’ve known since my teen years that I prefer lifting to running. I was a good wrestler in high school—due mainly to lifting—but I hated the mandatory run around the football field after practice. My dad was the same way; he was good at pole vaulting, jumping, and throwing the discus, but had no interest (or aptitude) in running any distance.

Most people are probably in the middle or tilt a little one way or the other. After you exercise for a while, you’ll have a pretty good idea where you fall on the spectrum between strength and endurance. We almost always enjoy what we do best. Few people are willing to do things they don’t enjoy for very long.

Dr. Kenneth Cooper’s book Aerobics, published in 1968, convinced me that aerobic exercise is important. Carol and I have been doing some form of aerobic exercise ever since, a little running, but mostly biking, hiking, and walking. I was never really into aerobic exercise—until I discovered indoor rowing and later interval training. Rowing and interval training excited me, because they afforded me the option of doing short, hard workouts, akin to lifting. They have a major strength component. That’s what I enjoy and do best; it’s my thing.

I’ve got plenty of company. Many people just can’t get excited about jogging and the like, probably because there’s no challenge or they’re not very good at it. They end up doing aerobic exercise sporadically or not at all. Many never find a form of aerobic exercise that they enjoy and do well. The same goes for strength training; some people find it unappealing. Fortunately, new options are opening up in both forms of exercise.

For example, people who can’t see themselves lifting heavy weights are discovering effort based lifting, which provides the same benefits with light weights or other forms of resistance training; see Lifting—Many Ways that Work:  http://www.cbass.com/LiftingWithEffort.htm

We need both strength and endurance to be totally fit and healthy—and we can almost always achieve both in ways that suit our body and personality.

The new findings on the synergy between resistance and endurance exercise will open up new options that make it easier to become totally fit and healthy.

Take charge—find the way or ways that suit you best.

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