Research review: Muscular adaptations in response to three different resistance-training regimens

A while back, I mentioned in my research review of the study Disproportionate changes in skeletal muscle strength and size with resistance training and ageing, that I would look in more detail at the fact that strength training causes a shift from type two to type one muscle fibres (yes, you read that correctly).

So here is the main study I referred to back then.  It is called Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones, Campos, Luecke, Wendeln, Toma, Hagerman, Murray, Ragg, Ratamess, Kraemer and Staron, European Journal of Applied Physiology, 2002.

Let’s dive straight into what the researchers did.

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What did the researchers do?

The researchers took 27 healthy strength training beginners and divided them into three training groups for an eight week, lower-body resistance training programme, performing the squat, leg extension and the leg press as follows:

• Low repetition – 4 sets of 3-5 reps with 3 mins rest
• Medium repetition – 3 sets of 9-11 reps with 2 mins rest
• High repetition – 2 sets of 20-28 reps with 1 min rest

There was also a control group that just sat around on their asses doing nothing.  Amusingly, one of the control group couldn’t sit on his ass for eight weeks and started going to the gym, after which he was summarily dropped from the study…  Anyway, the subjects carried out two workouts per week for the first four weeks and three workouts per week for the second four weeks.

And directly after this extremely arduous strength training programme, they looked exactly like this (minus the majestic beard, obviously)… or maybe not.

Hercules probably didn’t take a low-volume approach (photo by Averain)

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So our bold and hard-working researchers took quite a few different measurements before and after the eight-week lower-body strength training programme.  The measurements before and after were:

• Body mass
• Lean body mass
• Body fat percentage
• VO2-max
• Aerobic power (W)
• 1RM
• Repetition max at 60% of 1RM
• Fibre type analysis (from a muscle biopsy)
• Cross-sectional area (from a muscle biopsy)
• Myosin heavy chain analysis (from a muscle biopsy)
• Capillary density (from a muscle biopsy)

That must have been quite a lot of work for all of those subjects!  Let’s take a look at the results now.

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OK, what were the results?

Well, to summarise the results very quickly, without getting into too much detail where we don’t need to, this is what happened:

Body mass – all groups increased body mass (control – 0.6kg, low – 2.3kg, medium – 1.7kg, high – 1.3kg).  The researchers did not judge these changes to be significant.

Body fat percentage – the strength training groups all increased body fat percentages (low – 0.4%, medium – 1.3%, high – 0.2%).  Again, these changes were not viewed to be significant.

VO2-max – VO2-max did not really change significantly for any of the groups.  However, this fact is interesting in light of the change in aerobic power below.

Aerobic power (W) – despite there being no changes in VO2-max, aerobic power increased significantly in the resistance training groups (low – 10W, medium – 3W, high – 43W).  Bearing in mind that this study was done back in 2002, the researchers found this result a little troubling and justified it by noting that “although this may seem to contradict the basic principles of training specificity, enhanced long-term work capacity also requires muscular strength and anaerobic power.” They also noted a study that showed resistance training improved running economy and wondered whether it could also improve cycling economy.  Of course, we now know that this is possible thanks to more recent research.

1RM – maximum strength increased just like you’d expect, most for the low rep group, least for the high rep group and somewhere in the middle for the medium rep group.

Repetition max at 60% of 1RM – similarly, the rep max improvements were the inverse of the 1RM improvements.

Fibre type analysis – so in all three resistance training groups, the only really significant movements in fibre composition between pre- and post- eight week training period occured between type IIAB and type IIB fibres.  For all three groups, the percentage of type IIB fibres reduced greatly and the percentage of type IIAB fibres increased significantly.  And we are not talking about small movements here, either.  In only eight weeks, the percentage of type IIB fibres halved and the percentage of type IIAB fibres doubled for all groups.

So the two key points here are: (1) the three protocols all led to the same changes in fibre type, (2) the fibre type changes on the fast-slow continuum were in the slower direction.

Cross-sectional area – the cross-sectional area of the muscles increased only for the low and medium rep groups.  For these two training groups, the cross-sectional areas of all three major fibre types (I, IIA, and IIB) were significantly larger after training (c. 12.5% for type I, 19.5% for type IIA, and 26% for type IIB).

So despite the percentage fibre composition changes being the same as the other two groups, the high rep group didn’t experience the same hypertrophy changes.

Capillary density – despite this being a staple question for basic personal training muscular adaptations to resistance training course material, the researchers did not note any significant changes to capillary density in any of the subjects.

 The subjects became unstoppable after their eight weeks hard training                      (photo by RobinElaine) 

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What’s all that about type IIAB and type IIB?

It’s really nothing that complicated although if you get into the research methods of how they figure out what each fibre is classified as, it can get horrible in a hurry (a good summary can be found here).  Anyway, briefly, originally, muscle fibre types were divided into three classifications:

• Type I – slow
• Type IIA – intermediate
• Type IIB – fast

However, scientific advances have now resulted in seven fibre types being differentiated, as follows:

• Type I
• Type IC
• Type IIC
• Type IIAC
• Type IIA
• Type IIAB
•  Type IIB

Essentially, the same rules apply as for the three types.  The further down the list you go, the faster-twitch the fibre and the more powerful it is.  The interesting thing is that the resistance training methods seems to make the fibre composition less powerful rather than more powerful.

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Wrapping up

So the things that interest me here are:

• Why do the three different protocols lead to the same fibre type changes?  Are we looking in the wrong place when it comes to differentiating the muscle types of different athletes?
• Why does the body do something that is counter-intuitive for strength gains when tested with low repetitions such as 3-5 reps?  Is the protocol too high rep?  Would the same fibre-type change happen with singles or plyometrics, for example?  Fortunately, I have a study up my sleeve for tomorrow that should help us answer this question.