Research review: Effects of heavy-resistance training on hormonal response patterns in younger vs. older men

Last week, we took a look at a large review article on the hormonal changes that occur following lifting weights.

One of the interesting things that popped up in that review article was that greater rises in growth hormone occur by adding a single set of higher reps to your normal low-rep strength sets.  So 5 sets of 3 reps caused a much smaller rise in growth hormone than 5 sets of 3 reps followed by a set of 20 reps with a lower weight.  To get to the bottom of this issue, I looked at a short study on muscular adaptations to different combinations of high and low intensity exercise.

However, there was clearly a lot more to go at, so let’s take a look at a couple more studies on the same subject this week.

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So what’s the study today?

Today’s study is on a subject close to my heart, resistance training and sarcopenia, or the effect of ageing on muscle mass.  As regular readers will know, I hate the idea prevalent in today’s day and age that people must inevitably become immobile and frail as they get older.  It’s such a horrible waste of life.  Seeing people just shrug and accept it breaks my heart.

The study today is called Effects of heavy-resistance training on hormonal response patterns in younger vs. older men, by Kraemer, Hakkinen, Newton, Nindl, Volek, McCormick, Gotshalk, Gordon, Fleck, Campbell, Putukian and Evans, in Journal of Applied Physiology, 1999.

The ageing process is an unpleasant phenomenon that causes:

• Sarcopenia (muscle wastage)
• Reductions in muscular strength
• Reductions in plasma concentrations of circulating anabolic hormones and growth factors

Fortunately, a number of studies have found that resistance training can address sarcopenia by increasing muscle mass even in older men.  But what about the endocrine changes?  To find out, this study sets out to discover whether the right resistance training programme could also enhance the resting and exercise-induced endocrine responses to resistance exercise.

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So what did the researchers do?

The researchers took eight 30-year old subjects and nine 62-year old subjects and took measurements before and after a 10-week periodised strength training programme.

The periodized resistance training programme was performed three times per week for 10 weeks.  The workouts were alternated by varying the resistance and the volume over the week.  How did this pan out?

• Monday, sets were performed at 3–5 RM with 2–3 min of rest between sets,
• Wednesday, sets were performed at 8–10 RM with 1 min of rest between sets,
• Friday, the load was 12–15 RM, however, only 6–8 repetitions were performed with the intention of performing these exercises with greater power output or in an explosive manner with 1–2 min of rest.

The programme was a full body workout consisting of squats, knee extensions, lower back extensions, lat pull downs, leg curls, calf raises, bench presses, seated rows, military presses and arm curls.

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And what happened?

Strength

The strength improvements (1RM squat) were:

• 30-year olds – 139 +/- 22kg to 163 +/- 23kg – an improvement of 24kg (17%)
• 62-year olds – 102 +/- 34 to 113 +/- 37 kg – an improvement of 11kg (11%)

So the 30-year olds improved their strength by more than twice as much in absolute terms in the same period of time, using the same programme.  However, in percentage terms, the improvement was much less marked.

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Hypertrophy

The hypertrophy improvements were measured using thigh muscle cross-sectional area and were as follows:

• 30-year olds - 186 +/- 16cm sq to 204 +/- 18cm sq, an increase of 18 cm sq (9.7%)
• 62-year olds - 159 +/- 26cm sq to 169 +/- 26cm sq, an increase of 10 cm sq (6.9%)

So the 30-year olds improved their strength by nearly twice as much in absolute terms in the same period of time, using the same programme.  However, again, in percentage terms, the improvement was much less marked.

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Hormones

Various measurements were taken for hormonal concentrations and the following significant results noted:

• Resting free testosterone rose over 10 weeks – the weight training programme appears to have raised the resting free testosterone (but not total testosterone) significantly for the 30-year olds (but not the 62-year olds) over the 10 weeks.  This is interesting as it did not crop up in the review article I looked at last week.
• Resting cortisol decreased for both groups over 10 weeks – the weight training programme appears to have lowered the cortisol levels of both groups over the 10 weeks, with the 62-year old group having a much larger decrease.
• Testosterone rose in both groups after exercise – after heavy resistance exercise, the testosterone levels of both groups rose, although the levels of the 30-year olds rose higher
• Cortisol rose in both groups after exercise - after heavy resistance exercise, the cortisol levels of both groups rose and remained elevated after one hour and there were no significant differences between groups
• Testosterone levels post-exercise rose more after the 10-weeks – in both groups, the post-exercise testosterone levels of both groups rose more after the 10-week training programme than before.  So the immediate response was increased by the training programme.  However, again, the increase of the 30-year olds was greater.
• Cortisol levels post-exercise dropped more after the 10-weeks – in both groups, the post-exercise cortisol levels was less elevated after the 10-week training programme than before.  So the immediate response was decreased by the training programme.  However, the amount by which the cortisol response decreased was much smaller in the 62-year old group.

All of these significant findings led to the researchers getting very excited about this study.

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The researchers got excited about testosterone

The researchers appeared to be very excited about the comparatively greater ability of the younger men to elicit a greater relative hypertrophic response in 10 weeks of training.  They believe that this study shows that this greater ability is associated with the differences in the resting and exercise-induced adaptational patterns of the hormones.

In particular, they were excited by the movements in total and free testosterone.  They note that in men, testosterone is a potent anabolic hormone that mediates protein accretion and also enhances neural function.  Their key points are:

• Exercise-induced levels of total testosterone - in their study, exercised-induced concentrations of testosterone were significantly higher in the 30-year old group than in the 62-year old group.
• Exercise-induced levels of free testosterone - area-under-the-curve analysis in their study revealed a greater magnitude of increase in the exercise-induced responses of free testosterone to a resistance training stimulus in younger men.

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The researchers got excited about the andropause

As a result of their conclusions about testosterone being the driving factor behind the difference in hypertrophy and strength gains between the young and old groups, the researchers assert that these data support the maintenance of an male menopause or andropause, which is characterised by:

• a decrease in testicular Leydig cell numbers,
• reductions in secretory capacity, and
• a decrease in resting episodic and stimulated gonadotropin secretion.

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The researchers got excited about testosterone and lactate

So if the 62-year old group had suffered the andropause, how was testosterone still being raised by exercises?  The researchers point to another study that may have the answer, Lactate and the effects of exercise on testosterone secretion: evidence for the involvement of a cAMP mediated mechanism, Lu, Pang, Tung, Huang, Chen, Shih, Tsai, Lu, Wang, Chen, Chien, Chien, and Wang, in Medince and Science in Sports and Exercise, 1997.

Lu et al. reported that increased testosterone concentrations in male rats during exercise were at least partially the result of a direct stimulatory mechanism of exercise, with lactate influencing the secretion of testosterone by increasing testicular cAMP production.

This is very interesting, as it provides some support for the idea that older people need to work more in traditional bodybuilding rep ranges to focus on hypertrophy rather than strength.

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The researchers get excited about cortisol

The two key points regarding cortisol are:

• The older men experienced a resting decrease in cortisol over the 10-week period that was greater than the younger men (this occured without a corresponding decrease in its precursor, the adrenocorticotropic hormone – ACTH).
• The younger men experienced a post-exercise response in cortisol that was muted after the 10-week period compared with the older men.

The researchers draw certain conclusions based on this data, including:

• The resting decrease in cortisol over the 10-week period for the older men without a corresponding decrease in ACTH may be caused by a downregulating of ACTH activity.
• The greater reductions in cortisol experienced by the younger men post-exercise have been thought to provide one possible mechanism by which the younger men gained more muscle than the older men.

I don’t really see these observations as particularly interesting.  I think the results are fascinating, however.  And I think that they may well tie into Per Bjorntorp’s theory of the inflexible HPA axis.  Please let me explain…

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An inflexible HPA axis causes low testosterone

Per Bjorntorp believed that the key to good health was the flexibility of the HPA axis (i.e. its ability to move up or down over the course of the day) and not whether it was up or down (i.e. whether cortisol was high or low).

For those of you who don’t remember my extensive stress series, the HPA axis is the hypothalamic-pituitary-adrenocortical axis and works as follows: the hypothalamus secretes corticotropin-releasing hormone (CRH).  This molecule travels through to the anterior pituitary gland, which responds to its presence by secreting a pulse of adrenocorticotropic hormone (ACTH).  The ACTH signal is carried through the to the adrenal glands, which synthesise and release cortisol.

In talking about obesity, Bjorntorp says: “the perturbed regulation of the HPA axis rather than elevated cortisol secretion might be the crux of the matter in attempts to understand how cortisol secretion is associated with metabolic abnormalities.”  So the inflexibility of the HPA axis may be responsible for poor body composition and the feminising effect of obesity in men.

And furthermore, Bjorntorp explains that “it seems possible that the diminished secretions of sex steroid and growth hormones are involved. Deficiencies in these hormones would be expected to be followed by similar consequences as elevated cortisol.”  So the inflexibility of the HPA axis is linked to low testosterone.

Which makes me wonder whether inflexibility of the HPA axis is causing these observations by the researchers in older men.

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 Wrapping up

There is a lot to think about in this study.  However, I think there are a couple of key points, as follows:

• Older men (62 years old) can significantly gain both strength and muscle using resistance training
• Testosterone is associated with greater muscle gain
• Free (but not total) testosterone can be increased in younger men through resistance training (but note that not many studies show this)
• HPA axis inflexibility (bad cortisol response) may well be associated with less muscle gain (possibly because it is linked to low testosterone)
• Lactate may be associated with testosterone response after exercise, particularly in older men, suggesting that higher reps might be better for older men

So for me, the take-home points are:

• Testosterone is really important for muscle gain
• Stress may be even more important than I previously thought, insofar as it controls the flexibility of the HPA axis and therefore impacts on testosterone levels
• Higher reps (to create lactate) may be important for older men to generate a better testosterone response

There’s another hormone-related research study coming up tomorrow.  After that, I’m going to look at something else for a bit…