Category: Strength

Strength: articles about getting strong: pushing, pulling, and lifting more weight.

Vitamin D, Muscle, and Testosterone

My regular readers know I don’t put much faith in supplements.  I have a very short list of supplements that work, and I’m very skeptical of bodybuilding supplements in general.  But Vitamin D is one I think every trainee should consider taking.  Here’s an overview:

Vitamin d plays a crucial role building both bone and muscle. We synthesize it when our skin is exposed to sunlight.  We also get it from food (or supplementation, which I will discuss later).

Deficiencies are associated with obesity and weaker muscles–this correlation has been shown through many studies over the years.

Studies have also  shown a positive correlation between levels of vitamin d and sex hormones (both men and women).1  Supplementing with this micro-nutrient, for example, seems to raise testosterone levels in men who are deficient.2

Vitamin d deficiency is very common, probably affecting half of the world’s population.3  Americans are not exceptions to this statistic.  A 2010 study revealed that 24% of the subjects tested (90 young women in California) were deficient in vitamin d, and even more (59%) were at “insufficient” levels (< or = 29 ng/ml).  Those with low levels of vitamin d had a higher % of fat within their muscles (“muscle adiposity”).4

So let’s put all this together:

1. Vitamin d that plays a crucial role in both muscular strength, leanness, and optimum hormone levels (like testosterone).

2. There’s a possibility you are deficient in it.

Here are a few of the factors that would tend to affect your levels of vitamin d:

*Skin tone: melanin protects from sun damage but also limits synthesis (darker skin=higher risk for deficiency).

*Sun exposure: the amount time you spend in the sun, the climate you live in, and the season (summer vs winter) all affect how much vitamin d you produce.

*Age: our ability to produce this vitamin declines with age.

Supplementation:

One study demonstrated supplementing with 800-1000 mg/day way sufficient to improve the strength and balance of elderly patients. 5 The study I quoted earlier (re: raising testosterone levels) used about 3,000 mg/day.  I doubt any adult would have any issues supplementing in the 1,000-3,000 range–the institute of medicine puts the upper level of recommended supplementation at 4,000 mg/day.6  Vitamin D-3 seems to be the best choice as in terms of the type/form of supplement. 7

I use the NOW Foods Vitamin D-3, Structural Support 2000 I.U., 240 Softgels, but any reputable brand would do.

Having said this, I’d highly recommend you ask your doctor for a blood test to know exactly what your blood levels are.  This is the only way to know for sure and develop a precise strategy (supplementation, etc).

References:
1.Eur J Endocrinol. 2012 May;166(5):765-78. Epub 2012 Jan 24.  Vitamin D and fertility: a systematic review.

2. Horm Metab Res. 2011 Mar;43(3):223-5. Epub 2010 Dec 10. Effect of vitamin D supplementation on testosterone levels in men.

3. J Pharmacol Pharmacother. 2012 Apr;3(2):118-26. Vitamin D: The “sunshine” vitamin.

4. J Clin Endocrinol Metab. 2010 Apr;95(4):1595-601. Epub 2010 Feb 17. Vitamin D status and its relation to muscle mass and muscle fat in young women.

5. J Am Geriatr Soc. 2011 Dec;59(12):2291-300. doi: 10.1111/j.1532-5415.2011.03733.x. Effect of vitamin D supplementation on muscle strength, gait and balance in older adults: a systematic review and meta-analysis.

6. Institute of Medicine: Dietary Reference Intakes for Calcium and Vitamin D

7. J Clin Endocrinol Metab. 2011 Mar;96(3):E447-52. Epub 2010 Dec 22. Vitamin D(3) is more potent than vitamin D(2) in humans.

Knee Wraps: should you use them for squats?

A while back I wrote about using wrist wraps to prevent pain with pressing movements (bench press, etc.).

I’ve also used knee wraps occasionally without any ill effects.  But I’ll probably put them away for good after reading an article that was published in the Journal of Strength Conditioning.  Researchers compared the squatting technique of resistance trained men in the squat with and without the assistance of knee wraps (using 80% of their one rep max).  The wraps did increase the “mechanical output” (meaning it would help lift heavier weights).  But it also possibly increased their chances of injury:

“The elastic properties of knee wraps increased mechanical output but altered back squat technique in a way that is likely to alter the musculature targeted by the exercise and possibly compromise the integrity of the knee joint. Knee wraps should not be worn during the strength and condition process, and perceived weakness in the knee joint should be assessed and treated.”1

This is a simple risk/benefit issue.  If you are a competitive powerlifter then you’ll want to use every advantage possible to lift more weight.  Otherwise you may want to consider doing some (or most) of your lifting without wraps.

There is another option I haven’t mentioned here: knee sleeves.  Using these may be a happy medium,  providing some support (and keeping your joints warm) without altering the mechanics of the lift.  I’m just speculating here, since no research has been done on squatting with sleeves (that I’m aware of).

Reference:

1. J Strength Cond Res. 2012 Oct;26(10):2844-9. Wearing knee wraps affects mechanical output and performance characteristics of back squat exercise.