This study examined a programme of pre-conditioning exercise with subsequent high intensity interval training (HIIT) on blood pressure, echocardiography, cardiac strain mechanics and maximal metabolic (MET) capacity in sedentary (SED) aging men compared with age matched masters athletes (LEX).
A programme of preconditioning exercise with HIIT induces clinically relevant improvements in blood pressure, rate pressure product and encourages recovery of heart rate reserve in SED, while improving maximal MET capacity in both SED and LEX without inducing any pathological cardiovascular remodeling. These data add to the emerging repute of HIIT as a safe and promising exercise prescription to improve cardiovascular function and metabolic capacity in sedentary aging.
Normal aging is accompanied by diffuse alterations to cardiovascular structure and function that contrive to increase cardiovascular morbidity and mortality during advancing years. Since the landmark Dallas bed-rest study (Saltin et al., 1968), the pleiotropic effects of preserving cardiorespiratory fitness (CRF) during advancing age have become more widely appreciated such that achievable improvements in CRF (~ 1 MET) can profoundly impact health and survival (Kaminsky et al., 2013; Kodama et al., 2009) by improving CRF through effective physical activity regimens. However, because epidemiological studies consistently identify older adults as the least physically active demographic (Knowles et al., 2015) and because CRF is a greater prognostic indicator of mortality than ‘physical activity’ (Lee et al., 2010), then alternative strategies that improve CRF in older persons have become increasingly important.
High-intensity interval training (HIIT), is characterized by brief, intermittent bursts of vigorous exercise, interspersed by periods of low intensity recovery (Saltin et al., 1968). More recently, HIIT has meta-analytical support as a viable method to improve cardiovascular health by increasing cardiorespiratory fitness (CRF) in young healthy (Weston et al., 2014) and cohorts with lifestyle-induced cardiometabolic disease (Elliott et al., 2015; Weston et al., 2013). Of the few available data in older cohorts, HIIT appears to offer promising results in patients with coronary artery disease (Munk et al., 2009), following myocardial infarction (Moholdt et al., 2009) and hypertension (Molmen-Hansen et al., 2012) but there is an absence of data in sedentary aging (Weston et al., 2014). Of contrasting note, a recent experiment described the potential for to HIIT to promote pathological adaptations in the left ventricle of hypertensive rats (Holloway et al., 2015), underlining the need for further study of HIIT on cardiac structure, hemodynamic strain and strain mechanics in sedentary aging.
Encouragingly, both the feasibility of HIIT and its prescription following an initial period of conditioning exercise have recently been established in aging cohorts (Knowles et al., 2015; Sculthorpe et al., 2017). However, because aging men can take longer to recover from single strenuous HIIT session than their younger counterparts (Herbert et al., 2015a), caution should be exercised when prescribing the volume of HIIT training in aging cohorts. With these aspects in mind, the present study set out to examine the effects of low frequency HIIT (once every 5 days) on: i) resting cardiac structure and function ii) blood pressure and rate pressure product, and iii) metabolic capacity (MET’s) in a cohort of sedentary but otherwise healthy aging men (SED). These were compared with a positive control group of age-matched lifelong exercising masters athletes (LEX). We hypothesized that 6 weeks (9 sessions) of low frequency HIIT would (i) not alter cardiac structure or strain mechanics (ii) would favourably affect indicators of resting blood pressure and rate pressure product in SED compared with LEX. We further hypothesized that HIIT would (iii) positively impact maximal metabolic capacity (MET’s) in SED compared with LEX.
Using a STROBE compliant observational design, 39 aging male participants (SED; n = 22, aged 62.7 ± 5.2 yrs) (LEX; n = 17, aged = 61.1 ± 5.4 yrs) were recruited to a study that necessitated three distinct assessment phases; enrolment (Phase A), following pre-conditioning exercise in SED (Phase B), then following 6 weeks of HIIT performed once every five days by both groups before reassessment (Phase C). Hemodynamic, echocardiographic and cardiac strain mechanics were obtained at rest and maximal cardiorespiratory and chronotropic responses were obtained at each measurement phase.
The training intervention improved systolic, mean arterial blood pressure, rate pressure product and heart rate reserve (each P < 0.05) in SED and increased MET capacity in both SED and LEX (P < 0.01) which was amplified by HIIT. Echocardiography and cardiac strain measures were unremarkable apart from trivial increase to intra-ventricular septum diastole (IVSd) (P < 0.05) and decrease to left ventricular internal dimension diastole (LVId) (P < 0.05) in LEX following HIIT. Source: Experimental Gerontology