Not Just a Man's World

I’ve been wondering about creatine for a while now. Chris keeps some in the cupboard and I’ve considered taking it from time to time.  So far, despite the creatine being in the cupboard for several years, I’ve not tried it.  Part of my reluctance comes from a poor understanding of what it might do to help me and, in fact, whether it is much use at all for women.  So this is a study that should help with my understanding.

Creatine is mostly found in our skeletal muscle tissue and is actually produced naturally by our bodies, mostly in the kidney and liver from amino acids before being transported through the blood to the muscles for storage and use as an energy source.  This storage of creatine in the muscles not only means that it provides greater muscle energy stores, usually allowing people to do more work and therefore build more strength, but also creates larger muscles in appearance because it increases water retention in the muscles (in a similar way to carbohydrates).  As a result it is used not only by athletes and lifters looking to build strength but also by bodybuilders to increase muscle size.

All vertebrates contain this creatine and as a result people consuming quantities of meat and fish will already be getting some natural supplementation of creatine.  This is another reason that I’ve been sat on the fence about creatine supplementation.  I consume a pretty large portion of one of those every day, most often red meat or chicken, fish is less frequent except when I’m having a tuna phase.  As a result, I’m not convinced that supplementing with additional creatine would benefit me.

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The effect of creatine supplementation during resistance training in women

Brenner M, Walberg Rankin J W, Sebolt D.  Journal of Strength and Conditioning Research 2000; 14(2), 207-213.  (Free copy of the study here.)

Background to the study

Creatine supplementation is used to build muscle.  It is a natural element within our muscles but sometimes it benefits from a bit of a boost.  Several studies, referred to in this paper, have shown benefits of short periods of creatine supplementation (often one week of supplementation) on maximal isometric muscle strength, single sprints and maximal effort, repeated sprint exercise.  What had been researched less when this study was published, was the longer-term effects of creatine supplementation when it is taken in smaller dosage for a longer period.  As the authors note, most athletes who supplement with creatine will use it throughout the season so it is “of interest to know whether longer-term creatine consumption will enhance the effects of training”.  While previous studies had looked at longer-term use in various male athletes there had been limited research into the effects on women.  One study had looked at “women consuming creatine along with resistance training”, but this study had been carried out with previously untrained women.  While that study had shown that the women taking the creatine had 20-25% greater increases in 1RM for 3 of the 7 exercises tested after 10 weeks of resistance training a new trainee is unlikely to throw themselves into supplementing with creatine.  Creatine supplementation is more often found among athletes so it is more relevant to look at the effects of the supplementation for athletes, especially since new trainees in resistance training, especially women, see some huge strength benefits just from taking up resistance training.

Participants

Our athletic participants this week were sourced from Division 1 of the NCAA women lacrosse team.  20 players volunteered, all of them between the ages of 18 and 22.  Why use this particular team?  Well, as the paper notes, one of the coauthors was an assistance coach.  Since this meant that she saw the team members every day she could remind them to take their supplementation and therefore increase compliance and adherence.

Another benefit of using members of the same team was that they had similar established training routines set out by the team strength coach and trained under supervision, presumably at fixed team training times.  To complete the study 85% attendance was required and four women were excluded from the study by the end due to illness (two women), injury and, in one case, because she left the team.  Sadly three of these women were in the creatine supplementing group so by the end there was a mismatch in numbers with seven women in the creatine group and nine in the placebo group.

What were the authors measuring?

The authors were considering the effects of creatine supplementation on two areas with this study.  Athletic performance and body composition.

Performance

For this study the authors were measuring muscle performance as both strength and endurance.

Strength was measured through 1RM testing of free-weight bench press and Nautilus leg extension.  This testing was done on days 3 and 39 of the study.

Muscle endurance was measured on days 2 and 38.  This was done through completion of 5 sets of 30 repetitions of a unilateral isokinetic knee extension at 180 degrees per second with 1 minute rest between sets.  Their dominant leg was attached to the machine and the calculations are explained in the paper by the authors as follows:

“Total work performed, as well as an index of muscle fatigue, were calculated from this test. Work fatigue within the first and last set was calculated by subtracting the work output of the last 10 repetitions from the work output in the first 10 repetitions, divided by the work output in the first 10 repetitions. Fatigue for the performance test was calculated by determining the work fatigue during the fifth set as a percentage of work fatigue during the first set. Total work was the sum of the work done during each of the 5 sets.”

A finger prick blood sample was also taken 3 minutes after the muscle endurance tests on days 2 and 38 in order to look at the blood lactate accumulation, as previous creatine studies had suggested improvements (eg. reductions) in blood lactate levels for those supplementing with creatine.  There were a few other medical samples and tests carried out but I’m not going to linger on those here.

Body composition

The body composition changes were measured through the following methods:

• body weight measurement on days 1, 2, and 38 after an overnight fast each time
• body density on days 1 and 38 using hydrodensitometry
• body density estimations (presumably on the same days – days 1 and 38 – although they don’t state that) using skinfold measurements.

Training

The participants trained on Monday, Wednesday and Friday each week.  At the training they completed two main exercises – free-weight bench press and Nautilus leg extension cycle – starting in week 1 with 4 sets of 10 repetitions at 40–60% of 1RM (3–5 minutes between sets) and increasing intensity and number of sets over the 5 weeks of the study until they were performing 5 sets at 50, 75, 80, and 85% of 1RM (10 repetitions for the first set and 5 for the other sets) by the end of the study period.

In addition to these two main exercises the women were also doing the following free-weight exercises:

• bicep curls (3 sets of 8 )
• tricep pushdowns (3 sets of 8 )
• lat pulldowns (3 sets of 8 )
• wrist curls (2 sets of 10)
• jump shrugs (3 sets of 10)
• medicine ball throws (2 sets of 10)

In each of these exercises they used the maximum loads they were able to work with while still completing the necessary sets and reps and without sacrificing technique.

Supplementation protocol

So how was the creatine supplemented?  It was a double-blind study, so the women and those providing the supplements to them didn’t know who was in which group, however when it comes to the detail of the how the supplements were given this paper is not, in my opinion, terribly clear.  After much reading, re-reading, and writing things out on bits of paper (and some assistance from Chris – thanks, Chris), I’ve worked out that the supplementation worked as follows.

• Days 1-3: no supplements – this is actually the pre-study period during which various base measurements were being taken.
• Days 4-10:  4 doses per day of 5g capsules, for the creatine group these contained creatine monohydrate, for the placebo group the tablets had identical appearance but contained sucrose.  Participants were instructed to take each of the capsules at least 3 hours apart for this period.
• Days 11-35:  1 dose per day of 2g capsules, again this was the same creatine monohydrate for the creatine group and identical sucrose-containing capsules for the placebo group.  Participants were instructed to take these single daily capsules in the morning.

Results

First up, I’ll start with things that, as far as the authors were concerned, did not differ significantly between the two groups: the change in total work or work fatigue and the blood lactate levels.  The implication being that muscular endurance and blood lactate levels are not improved by supplementing with creatine.

On the matters of muscular strength and body composition things get a bit more muddled.

The 1RM pre- and post-study for the leg extension shows similar rates of strength improvements in the two groups with no significant difference between them.  In comparison, the 1RM for bench press did increase significantly between the two groups: the creatine group saw a 6.2kg, 16.7% increase while the placebo group only saw a 2.8kg, 7.1% increase in their 1RM.

Figure 1. Bench press 1 repetition maximum (1RM) be- fore and after creatine supplementation. Values are averag- es with standard error of the mean. * 5 significant effect of time; # 5 significant interaction between group and time.

Both groups saw similar increases in body weight (0.5kg) with the hydrostatic weighing revealing no significant difference in the body fat percentage between the two groups.  However, there was a significant difference in percent body fat by skinfold technique with 85.7% of subjects in the creatine group decreasing their body fat and only 33.3% of subjects in the placebo group reducing their body fat.  Looking at the mean (average) values, the mean decrease for percent body fat by skinfold for the creatine group was 1.2%, while the placebo group slightly increased their average body fat by 0.3%.  It is worth noting that while the hydrostatic weighing did not show a significant difference, there was still a trend in movements that are similar to the skinfold technique, e.g. the hydrostatic weighing still showed a greater reduction in body fat for the creatine group when compared to the placebo group.

What do the authors have to say about these results?

The authors admit that their results are mixed, making it difficult to draw conclusions.  Where their results differ from other studies, which had showed significant improvements in the creatine groups, they put this down to the women in this study being more highly trained at the outset.  For example they state that “our subjects may have been closer to their maximal strength potential for leg extension [than in the previous study carried out with untrained women, which] may have limited any effect of creatine for this muscle group, while more opportunity to influence upper-body strength existed.”  The subtext I read into this is that if you are already highly trained woman then creatine is of limited use.

On the matter of the body composition changes, the authors advise in their discussion, “the reason for a difference in the statistical effect of creatine on body fat depending on technique used is not clear. However, it is important to note that the numerical trend was the same for both techniques (i.e., no change in P, decrease for C), but the variability in the measurement was greater for the hydrostatic weighing procedure.”

…and the health impacts?

Buried near the end of the discussion is a comment from the authors that I thought valuable to share.  A concern many people, especially women, have about new supplements they’ve not taken before is whether there might be negative impacts on other areas of their health.

In the discussion section of this paper the authors reported that there was no evidence of negative health effects from the creatine, with this supported by the lack of difference in results between the various other measures that they took, such as blood urea nitrogen.  The conclusion was that, at least for 5 weeks of usage, you shouldn’t see any bad side effects.

A dietary concern

Something interesting immediately stood out for me when I was reading the results of this study.  At the start of the results the authors summarise some of the data from the self-reported diet-health questionnaires that the women completed.  Remember that in my introduction I explained that those eating meat and fish (basically any vertebrate flesh) are already naturally supplementing with creatine as creatine is found in the muscle tissue of all vertebrates.

Shockingly (to me, anyway), 56% of the women in this study advised in the questionnaire that they were vegetarian (3/7 in the creatine group and 6/9 in the placebo group).  This mostly shocked me because of the athletic nature of what these women were doing, and perhaps because I’ve always been a happy carnivore by choice.

A further 24% were consuming red meat, poultry or fish less than twice a month so for the purposes of natural dietary creatine supplementation they were essentially vegetarians as well.  Unfortunately the authors don’t note the split of this 24% across the two groups but 24% knocks out another four participants.  Since we only had four left in the creatine group and three in the placebo group who were not vegetarian, there is potentially a big discrepancy between the two groups after considering the further 24% who are, as far as I’m concerned in this particular study, also vegetarian.

I’m concerned about this because it could affect the results.  For example, if the four women who are almost vegetarian divided out with three in the placebo group and one in the creatine group then we would have the results of the creatine group potentially compounded by the fact that three women in that group are not only taking the supplement but also have dietary supplementation of creatine, compared to zero creatine intake by any method in the placebo group.

This doesn’t make the results invalid, it just means that the results might not be quite as amazing as they first look and it also makes them less helpful to me, since I still can’t tell if my natural dietary creatine is sufficient.

If I were to hypothesize about the allocation of these four almost-vegetarians between the two groups, based on the bench press performance of the two groups at the outset, I might suggest that they were all in the creatine group, leaving the creatine group with no significant meat and fish eaters.  This would explain the much lower starting point of the 1RM in bench press for that group and the greater improvement levels to end up only slightly better than the placebo group (who in that scenario would contain three women with natural dietary creatine).  Again, creatine is clearly providing improvements, just not necessarily such relevant ones for a carnivore like me.

Of course, that last scenario is pure conjecture.  I would be fascinated to see the results split out further between vegetarian/almost-vegetarian women and the non-vegetarians.

Wrap up

So there you have it.  The results are fairly inconclusive and the implications for someone with a fairly high level of existing dietary creatine, thanks to a diet rich in meats and fish, are even more unclear.  There might be a benefit for upper body strength in trained women, though this could be because the lacrosse players were still relatively untrained in the upper body when compared to their lower body.  There might also be some benefit for body composition but, if there is, it is probably quite small compared to the body composition we’ve seen in some other studies – especially the milk and resistance training study.

It should be noted that this study is now quite old and a lot more work has been done with creatine since 2000.  As such I wouldn’t take this as a definitive study on the subject, but it certainly gives a flavour of the possible relevance of creatine for trained females.

I’m not sure, based on the results of this study, that creatine would have a significant-enough benefit for me to start taking it.  I would be interested to know if this study has changed your views on creatine or if you already take it and do see benefits from it, contrary to what I think we’re seeing in this study.