Box: Summary of Gaps and Opportunities for Future Research in the Area of Late Life Physical Resilience

Gap	Key Research Questions and Directions
Measurement of physical resilience	1) Approaches for assessing “resilient” and “resistant” functional trajectories
	2) Phenotypic measures that correlate to resilience—robustness versus frailty, fatigability or other whole body stress tests
	3) Difference in chronological versus “biological age”
	4) What is the best gold standard to validate new measures of physical resilience?
	5) How do we quantify the severity and chronicity of stressors?
Interactions between and across systems	1) Does low reserve across multiple systems affect physical resilience in ways that are additive, synergistic, or follow complex dynamical relationships?
	2) How do we assess reserve across multiple systems in an ethical manner?
	3) Does “reserve” in key systems influence the recovery phase, or merely affect the magnitude of perturbation from baseline?
Effective interventions to optimize resilience	1) Can we protect against future stressors by bolstering reserve and physical resilience during times of health?
	2) Are all types of reserve (or system-based resiliencies) equally important for all individuals or all types of stressors?
	3) During times of stress, what models of care or health interventions optimize physical resilience?
	4) Is there a role for Mithridatism in physical resilience (do low levels of health stressors increase resilience for future, more severe stressors)?