From the “and every day

From the "and every day my patients teach me something" book … an e-mail (actually, it was a "healinx" .. a new verb/noun in our office) .. today from a patient (reprinted here with consent, of course): 

I've settled into a routine of checking my BP after I get home from the YMCA, three or four mornings a week.  I alternate jogging days (usually 4.2 miles, sometimes more) with weightlifting days (about 16,000 lbs total).  I noticed that my systolic seemed higher on weights days than jogging days.  So, I decided to do a statistical comparison between the two.  This is a nice experimental design, because time of day, time after exercise (20-40 min), duration of exercise period (about 40 min) and other variables are pretty well equated.  (And I am equally exhausted after both.)  I first did an omnibus 2 x 3 factorial-design analysis of variance (ANOVA) with variables of exercise type and measure (systolic, diastolic, pulse rate). 

The exercise type x measure interaction was highly significant, F(2,28) = 30.915, p < .001.  Separate analysis of each measure confirmed that systolic was significantly higher after lifting (107.9) than after jogging (98.8), t(15) = 3.715, p = .002, BUT pulse rate was significantly lower after lifting (61.7) than after jogging (70.0), t(15) = 6.221, p < .001.  Diastolic did not differ significantly between lifting (58.9) and jogging (59.5), t(15) = .341, p = .742. 

I'm fascinated by the fact that the differences in systolic and pulse rate are so marked a half-hour after exercising.  Any thoughts on the implications of these results?  (Think we can get a publication out of this? Ha ha!).

 … and the distant physiology lectures from medical school seep back in.  (ooh . here's an interesting one )   Dynamic exercise (bike, walk, run,swim) involves high blood flow, and a decrease in peripheral resistance.   The body's responses to dynamic exercise are designed to get blood to active muscles, dissipate heat, and maintain blood supply to vital organs.  As acidity increases, (H+ and CO2 produced as metabolites of increased muscle contraction), bloow flow to the areas in "need" of blood flow will increase.  To as Total Peripheral Resistance (TPR) decreases … vasoconstriction will increase in inactive tissue .. diverting blood away from there and preferentially toward the organs in demand of oxygen.

… yet in isometric exercise, there is constant contraction, which limits blood flow.  This is primarily due to the mechanical occlusion of the vessels during contraction.  Blood pressure must therefore be increased to force blood through the contracted muscle. 

So dynamic exercise is thought to be better for lowering blood pressure, yet there remain compelling reasons to continue isometric exercise as well.