Failed Recovery of Glycemic Control and Myofibrillar Protein Synthesis With 2 wk of Physical Inactivity in Overweight, Prediabetic Older Adults.
Level 3 - non-randomized controlled study
Prospective single-arm before-after intervention study without a parallel control group.
PubMed 29095970 · doi:10.1093/gerona/glx203
What was done
Twenty-two overweight, prediabetic older adults (12 men, 10 women, mean age 69 ± 4 years) completed a three-phase protocol: 7 days of habitual baseline activity, 14 days of step reduction (<1,000 steps per day), and 14 days of recovery returning to habitual activity. Oral glucose tolerance testing was used to measure glycemic control (HOMA-IR, Matsuda insulin sensitivity index, and glucose/insulin area under the curve), and deuterated water ingestion was used to measure integrated rates of muscle protein synthesis.
What was found
Daily step count fell from 7,362 ± 3,294 at baseline to 991 ± 97 during step reduction, and returned to 7,117 ± 3,819 during recovery (all p < .05). Step reduction increased HOMA-IR, elevated glucose and insulin area under the curve, reduced the Matsuda index, and lowered integrated muscle protein synthesis. None of these markers returned to baseline levels during the 14-day recovery period (exact metabolic numbers and effect sizes were not reported in the abstract).
Why it matters
Brief periods of physical inactivity can trigger rapid metabolic worsening and reduced muscle protein synthesis in at-risk older adults that do not quickly reverse simply by returning to habitual walking.
Limits
The study had a small sample size (n = 22) and lacked a non-inactive control group. Findings are restricted to overweight, prediabetic older adults, and the abstract omitted numerical values and confidence intervals for metabolic and muscle protein synthesis endpoints.
Cited by
- supports In a 2017 study by Tanner Stokes and Chris McGlory in older pre-diabetic individuals, reducing daily steps below 1,000 for two weeks downregulated muscle protein synthesis and compromised insulin sensitivity, which failed to recover after two weeks of normal activity.