Isometric exercise training (IET) is the systematic use of isometric exercise in an evidence-based and scientifically sound programme specifically designed to achieve certain physiological adaptations, such as improving strength or muscular endurance.
The use of IET as a potential health treatment was not developed specifically by scientists, but as is so often the case, was initially observed in the context of our everyday activities. Specifically, the observation that there was a lower incidence of hypertension (high blood pressure) amongst men in jobs which involved moderate or heavy isometric activity (e.g. gripping to lift objects) regardless of age, social class, body composition or alcohol intake (Buck and Donner, 1985).
This seminal work threw down the gauntlet for researchers all over the world to further explore the potential antihypertensive benefits of isometric exercise.
Over the last decade, the main focus of our work in this area has been to investigate the effects of different isometric exercise training protocols upon blood pressure with the ultimate goal of providing both a prophylactic for those at risk of developing hypertension and an effective treatment for those already suffering from hypertension. Indeed, our findings increasingly support the contention that IET can provide a viable alternative for many individuals facing a lifetime of antihypertensive medication.
Whilst most people are aware that a number of lifestyle modifications are effective in the prevention and treatment of high blood pressure (NICE Guidelines 2011), it has recently been suggested that the role of physical activity is paramount (Carlson et al., 2014). For those who already appreciate this, aerobic exercise (e.g. jogging for 30 minute) is arguably the form of exercise most likely to be associated with antihypertensive benefits (Mancia et al., 2007). However, recent meta-analytic findings indicate that, when compared with aerobic exercise, which reduced resting SBP by 3.5 mmHg and DBP by 2.5 mmHg, IET resulted in significantly greater reductions of 10.9mmHg and 6.2 mmHg respectively (Cornelissen and Smart, 2013). To contextualise these findings, as little as a 2mmHg reduction in SBP or DBP can decrease the risk of hypertension by 17%, coronary heart disease by 5-6%, stroke by 15%, and all-cause mortality by 3% (Cook, Cohen, Hebert, Taylor and Hennekens, 1995; Stamler, 1997). In short, IET could be a very important treatment for hypertension.
In addition to this, and perhaps more saliently, IET is associated with a number of added psychosocial benefits, such as short exercise duration, ease of use, and unrestricted access, which collectively reduce some of the significant barriers to regular physical activity (Carlson 2014).
To date, our research group have demonstrated that resting blood pressure can be significantly reduced in normotensive participants following 8 weeks IET (Wiles et al., 2010) and then with as little as 4 weeks IET (Devereux et al., 2010) using bilateral leg extension. Our findings suggest that the efficacy of IET as a form of antihypertensive therapy is based upon the complex interaction of acute programme variables such as target muscles used, type of exercise, contraction style, exercise intensity, progressive overload and the integration of both short (between bouts) and long (between sessions) term recovery. These have been investigated extensively in healthy normotensive participants (Wiles et al., 2010; Devereux et al., 2010; Devereux et al., 2011; Devereux et al., 2012, Baross et al., 2012; Baross et al., 2013; Goldring, 2014; Devereaux et al.) to provide the necessary foundation for IET to be accurately and safely prescribed to the hypertensive population.
The search for the most effective isometric exercise training prescription has led us to explore a number of novel isometric exercise protocols (Wiles et al., 2005; Wiles et al. 2008; Wiles et al., 2010; Goldring et al., 2014,) with a special focus on prescribing this type of exercise in non-laboratory settings such as the home (Wiles et al., 2016). Indeed, in order to further facilitate isometric exercise prescription in the home we are also currently exploring the efficacy of prescribing wall squat intensity (angle) based upon an individual’s rating of perceived exertion (RPE) (John Lea, PhD.). This would allow the safe and reliable prescription of IET without the need for prior laboratory or medical testing or screening.
Our most recent findings demonstrate that 3 sessions of 4 x 2-minute isometric wall squat exercise performed at 95% of HRpeak (as ascertained during an incremental isometric walls squat test; Goldring, et al., 2014) over 4-week total training period, results in a statistically significant reduction in all parameters of resting and ambulatory blood pressure in pre-hypertensive participants (Taylor et al., 2018). Furthermore, exercising blood pressure for both diastolic (<115 mmHg) and systolic (<250 mmHg) stayed consistently within the ACSM exercise termination guidelines (Whaley et al., 2006) for all participants indicating the training protocol is also, relative to other forms of exercise, safe for use with a sub clinical (and potentially clinical) participant group. At present we are exploring the acute physiological responses to IE and the longer term adaptations to IET in female populations who are significantly underrepresented in the literature.