Have lived decades in an early 1970s 2-story 903 sq-ft condo with bathroom and 2 bedrooms upstairs plus a carport. Walking this light fit 135# body up and down is trivial effort. Much too active and coordinated to ever likely to fall on stairs even though I often do so in near darkness. Sometimes to strengthen my body before a winter ski season or a summer wilderness backpacking trip, may for a few weeks a few times each week, carry a 50 pound pack up and down stairs say a dozen times.
Below from 2012 negotiating a steep talus field at near 11k elevation. Now at age 76 and still doing this easily each summer that comes down to something very simple ...
USE IT OR LOSE IT.
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