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Biological Fitness - Functional Biomarkers
✅ Key Physical Metrics as Functional Biomarkers
1. Grip Strength
What it reflects: General muscle strength, frailty risk, all-cause mortality.
Evidence:
Lower grip strength predicts disability, hospitalizations, cardiovascular events, and mortality—even when adjusting for age and body size (Leong et al., 2015, The Lancet).
Reference Standards (Men, Women):
2. Sit-to-Stand Tests (Chair Rise)
What it reflects: Lower-body strength, power, and functional independence.
Evidence:
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≥15 seconds for 5 repetitions is associated with increased risk of mobility disability (Bohannon, 2012, Journal of Geriatric Physical Therapy).
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Time to complete 5 chair rises is highly predictive of mortality and falls.Reference
Standards:
3. Gait Speed (4-Meter or 6-Meter Walk)
What it reflects: Neuromuscular function, balance, overall health.
Evidence:
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Gait speed <1.0 m/s strongly predicts mortality and disability (Studenski et al., 2011, JAMA).
Reference Standards:
4. Standing Balance Tests
What it reflects: Proprioception, vestibular and neuromuscular function.
Tests:
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Single-leg stand: Eyes open ≥10 seconds.
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Tandem stance: Eyes open ≥30 seconds.
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Evidence:
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Shorter times predict falls, frailty, and disability (Vellas et al., 1997, Age and Ageing).
6. Power Tests (e.g. Vertical Jump, TUG)
Vertical Jump Height:
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Good proxy for lower-body power, which declines faster than strength with aging.
Timed Up-and-Go (TUG) Test:
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Normal ≤10 seconds.12 seconds indicates fall risk.
7. VO₂max (Cardiorespiratory Fitness)
Since you already mention VO₂max, it’s worth emphasizing that it remains the single best predictor of mortality across fitness domains (Kodama et al., 2009, JAMA). For functional “health,” thresholds roughly are:
Women:
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Under 30s: ≥40 ml/kg/min
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40–49: ≥35 ml/kg/min
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50–59: ≥30 ml/kg/min
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60–69: ≥25 ml/kg/min
Men:
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Under 30s: ≥45 ml/kg/min
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40–49: ≥40 ml/kg/min
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50–59: ≥35 ml/kg/min
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60–69: ≥30 ml/kg/min
Lower than these cutoffs correlates with higher morbidity risk.
🤔 Does Grip Strength “Cover Everything”?
Not quite. While grip strength is indeed highly predictive of all-cause mortality and is a terrific “global” proxy, it doesn’t fully capture:
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Lower-body strength/power (essential for mobility and fall prevention).
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Balance and stability.
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Aerobic capacity.
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Mobility and flexibility (joint range of motion, tissue extensibility).
Hence, a panel of functional tests, rather than one single measure, is scientifically preferable for defining “functional physical health.”
✅ Practical Takeaway
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Grip strength is a great screening marker but insufficient alone.
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Multidomain testing yields a far better functional picture—similar to using a blood lab panel rather than a single marker.
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Normative standards exist for all key functional domains and can be integrated into coaching for personalized benchmarks.
🧬 Functional Standards for “Biological Fitness”
In the spirit of your coaching on biological fitness, you could structure a minimal but powerful physical health “lab panel,” analogous to blood labs:
📚 Recommended References
Here are a few cornerstone papers and organizations for further detail:
European Working Group on Sarcopenia in Older People (EWGSOP2). Sarcopenia: revised European consensus. Age and Ageing, 2019.
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Leong DP, et al. Prognostic value of grip strength. The Lancet, 2015.
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Studenski S, et al. Gait speed and survival. JAMA, 2011.
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Kodama S, et al. Cardiorespiratory fitness and mortality. JAMA, 2009.
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Bohannon RW. Sit-to-Stand test review. J Geriatr Phys Ther., 2012.
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Vellas B, et al. Balance and fall risk. Age Ageing, 1997.