Yes. I think specific type of decline in muscle function can affect VO2Max readings and HR. The issue seems more complex than it might appear on first glance. On all of the occasions I can recall in the past few years, my lower body muscles were definitely the limiting factor in intense CV activity, including HIIT. On none of those occasions was I out of breath or in some cases even breathing hard. That profile is much different than when I was younger. The VO2Max readings may in one sense be accurate but, as we age, they may be measuring a different functional relationship and capacity.
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