Discussion
reductions in SBP (RPE-EX −, hypertension
BLOOD, HYPERTENSION, CARDIOVASCULAR DISEASE
The key findings of this pilot study were the clinically significant reductions in one or more BP measure in 100% of the intervention participants; this included significant reductions in both seated and supine resting measurements and significant reductions in ambulatory SBP. Blood pressure reductions matching or exceeding the MCID are associated with significant reductions in the risk of developing hypertension and cardiovascular disease (Prospective Studies Collaboration The current study demonstrated statistically significant reductions in resting supine (SBP: − 8 (− 5), DBP: − 8 (− 7), MAP: − 8 (− 7) mmHg) and seated (SBP: − 9 ± 6, DBP: − 6 ± 4, MAP: − 6 ± 3 mmHg) BP in the RPE-EX group; with similarly significant reductions in the supine (SBP: − 5 (− 4), MAP: − 5 (− 4) mmHg) and seated (SBP: − 14 ± 6, DBP: − 6 ± 4, MAP: − 8 ± 4 mmHg) BP measurements in the HR-EX group. When comparing the results of the current study to previous research, 4 weeks of IWS exercise produced resting BP reductions comparable or greater than those previously shown following 8 weeks of isometric hand grip (Badrov et al. The 24-h AMBP results showed significant reductions in SBP (RPE-EX − 8 ± 7 mmHg; HR-EX – 10 ± 4 mmHg) and non-statistically significant reductions in DBP (RPE-EX − 4 (− 3) mmHg; HR-EX − 3 (− 5) mmHg) and MAP (RPE-EX − 3 ± 3 mmHg; HR-EX − 3 ± 6 mmHg). Previously, Somani et al. (Comparison of each IWS protocol suggests that they were largely equally effective; indeed, there were no significant differences in any of the reductions between intervention groups. Ostensibly, the mean seated SBP reductions were greater, although non-statistically significantly, in the HR-EX group compared to RPE-EX (− 14 ± 6 mmHg vs. − 9 ± 6 mmHg respectively); however, this was likely due to the significantly greater baseline SBP recorded in HR-EX group. Alternatively, it is possible that the HR-EX method allows tighter control of and therefore a more consistent training stimulus between participants when compared to the RPE-EX method. Arguably, this is to be expected, given the use of maximal testing, HR monitoring and the lack of subjectivity in the exercise intensity measurement with the HR-EX method. However, it should be noted that 100% of RPE-EX participants did show MCID reductions. Therefore, more research is required to examine whether there is any advantage to the HR-EX method. In addition, even if the BP reductions and cardiovascular improvements using the RPE-EX method are more modest, it may still be that the accessibility of the RPE-EX method to a larger proportion of the target population, will make it an overall more effective intervention. It is also possible that participants that are introduced to this type of intervention via the more accessible RPE-EX method will then move on to using the more clinical HR-EX method for further improvements. Indeed, the aim of the RPE intervention is not necessarily to supersede the previous intervention, thus rendering it obsolete, but rather is to increase the overall impact of IWS interventions, by working concurrently to increase overall participation.A limitation to this study was the significantly greater baseline BP results and age in the HR-EX group when compared to the RPE-EX participants. It was not possible to counterbalance all participant characteristics in this study as too many existed for the number of participants; therefore, participants were randomised into groups prior to the first testing session (and before baseline BP measurement), with only sex being counterbalanced. Differences in baseline BP must be considered when analysing the effect of training interventions, as it has previously been demonstrated that more pronounced BP reductions occur in participants with higher baseline BP (Millar et al. 