Tuesday, July 22, 2014

How Strong is Strong Enough to Stay Healthy? If the Sum of Your 1RMs On Leg & Bench Press Don't Surpass Twice Your Body Weight Your Risk of Metabolic Syndrome Doubles

Don't worry, the sum of both your bench and leg press 1-RM must be ~2.5x your body weight, not each of the dumbbells you use, when you do DB bench presses ;-)
As a SuppVersity reader and Super Human Radio listener, you are well aware of the vital importance of physical strength as a determinant not just of the length, but also and more importantly of the quality of your life.

Scientist from the Manitoba Institute of Child Health have now conducted the first study that was specifically designed identify the threshold of muscle strength or rather weakness that would be associated with an increased likelihood of developing metabolic syndrome in men. As Martin Sénéchal and his colleagues point out, this threshold could be used to identify men at risk of chronic disease, before it's to late to intervene. Find out if you are strong enough!
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The scientists created receiver operating curves for muscle strength and the risk of MetS from a cross-sectional sample of 5685 young (<50 years) and 1541 older (>50 years) who enrolled in the Aerobics Center Longitudinal Study.

Table 1: Participant characteristics -- Continuous variables are presented as mean TSD, and categorical variables are presented a sn(%).
The primary outcome measure, the MetS, was defined according to the National Cholesterol Education Program Adult Treatment Panel III criteria. Upper and lower body muscle strength was treated as a composite measure of one-repetition maximum tests on bench and leg press and scaled to body weight.
"Low muscle strength was defined as the lowest age-specific 20th percentile, whereas high muscle strength was defined as composite muscle strength above the 20th percentile."(Sénéchal. 2014)
If you take a look at the baseline values in Table 1 on the right hand side of this paragraph, you will see that the older gentlemen in the study at hand were not just significantly unfitter, they were also fatter (waist circumference) and had - no wonder - a significantly higher rate of metabolic syndrome.

Against that background it's not surprising that the study found highly significant risk increases for metabolic syndrome in those subjects with low vs. moderate / high muscle strength. After adjustment  for age, smoking status, and alcohol intake young weaklings' risk of developing metabolic syndrome is 120% higher than that of stronger young men. For the older guys, things don't look much better.
How strong is strong enough? In order to avoid the significant increase in metabolic syndrome risk, young men have to leg press and bench press 2.86kg per kg of body weight. Older men (50+) must have an average lower body and upper body strength (assessed as 1-RM on supine bench press and seated leg press) of 2.46kg per kg body mass. With a 112% risk increase the weak 50+ agers are also more than twice as likely to develop metabolic strength.
Unsurprisingly, a further adjustment for cardiovascular fitness lead to a significant reduction of the associated risks from +120% and +112% to 23% and 32% respectively. In that, it is probably worth mentioning that strength appears to have a greater influence in older vs. younger men.

The significant impact of an adjustment for physical fitness, i.e. a measure that has all to do with cardio training (LISS / HIIT) and general physical activity and only very little with how much you lift on a 1-RM max effort should yet remind you that brute strength alone is not going to save you (fat) ass if you are one of the 21.8% of people who (dis)qualified as being inactive in their leisure time.
"Trying to Build Strength? Periodized Training Yields 30% / 34% / 77% Increases in Bench Press, Squat and Deadlift Performance" | read more
Bottom line: While we have long known that muscular weakness is a correlate of increased mortality and reduced quality of life in the elderly, the study at hand is the first to provide some orientation as to how strong you have to be to avoid health problems.

In that it may be surprising that the difference between young and old men is significantly lower than you'd expect: 14% or 0.4kg per kg body weight that's not exactly much and a value that tells us that the 65-year-old 95kg father of a 35-year-old 90kg son has to bench and leg press only ~10% less than his son (233.7 kg vs. 257.4 kg | for bench + leg press).

...What? Yes, I am pissed, too, but I hope that the scientists will soon come up with a similar study in women. I mean, we all know that muscle strength is nothing only men benefit from, right?
  • Sénéchal, Martin, et al. "Cut-Points of Muscle Strength Associated with Metabolic Syndrome in Men." Medicine & Science in Sports & Exercise (2014).