The article is available in open-access on the internet https://www.ahajournals.org/doi/pdf/10. ... 121.020980
What the researchers from the University of Colorado did was to subject one group of 18 persons to a low-resistance training of inspiratory muscles and another group of 18 persons to a high-resistance training. Resistance was defined as a percentage of the maximal inspiratory pressure (MIP). Low-resistance training was done at 15% of MIP ; high-resistance training was done at 65% (2 weeks) - 75% (4 weeks) of MIP. Not many people will know their MIP, because to measure it accurately will require special equipment. However, it may help to know that for the 36 participants aged 67 ± 2 yrs, the MIP was 64 ± 5 mm Hg at the start of the study. So low-resistance was at about 10 mm Hg and high-resistance at about 50 mm Hg. Wikipedia states "Typical maximum inspiratory pressures in adult males can be estimated from the equation, MIP = 142 - (1.03 x Age) cmH2O, where age is in years". Note that 1 cm H2O equals 0.74 mm Hg.
The results after 6 weeks of training were amazing :
- The systolic blood pressure of the HR group decreased significantly by 9 mm Hg ; the decrease of the LR-group was 3 mm Hg, which was judged insignificant by the authors
- The decrease in systolic blood pressure for the HR group was still present 6 weeks after the daily training was stopped ; the LR group had a slight increase in SBP
- The diameter of the brachial artery (the major blood vessel in the upper arm) had increased by 45% for the HR-group and was unchanged for the LR-group
- Blood serum samples taken from participants before and after the 6-week period showed a significant increase in nitric oxide (NO) generating activity for the HR group and much less for the LR-group. Wikipedia : "The endothelium (inner lining) of blood vessels uses nitric oxide to signal the surrounding smooth muscle to relax, resulting in vasodilation and increasing blood flow"
Now, what could be the relevance for rowing ? The study shows that a short, daily, high-resistance breathing excercise has substantial benefits. This is not what in-vogue polarized training schedules do. They typically combine 4 days of low intensity with 1 day of high intensity. Moreover, 75% of MIP is VERY high intensity that you cannot sustain very long in combination with a high power output. So in my view the polarized training should be complimented with a few minutes of separate high-resistance IMST training. You can do it in an armchair while watching television and there is no need for a towel to soak up the sweat.
What motivated this idea is an experience in cycling. I did several cross-country tours in the Rocky Mountains on dirt roads, such as the Great Divide route. At times the gradients and the weight of body+bike+gear is such that you get to the maximum of what you can sustain in speed and power output. The choice is between power pedaling or stepping down. The discipline of controlled, forced, maximal breathing is key. This is not what you do automatically in the first days. It takes a couple of weeks before breathing and pedalling are finely tuned. I observed that the altitude gain per hour hinges on disciplined breathing.
I start with a 6-weeks HR-breathing training today, mainly to reduce my systolic blood pressure (ca. 145 mm Hg). I wonder if there are others who do special trainings for breathing capacity.
Even if a reduction in blood pressure is not a motivator, the observations in the study on the effects on arteries and the production of nitric oxide are inspiring. What was observed for the main arteries in the arm will happen in the leg arteries too.
