Impact of applying different resting blood pressure cut-points to clear for maximal exercise

Abstract

OBJECTIVE:

The purpose of this study was to examine the impact of applying six commonly-used and two proposed resting blood pressure (BP) cut-points to clear individuals for maximal exercise in non-clinical health, wellness, commercial fitness agencies and physically demanding occupation test sites.

METHODS:

Participants (n = 1670) completed the Physical Activity Readiness Questionnaire for Everyone (PAR-Q+) and had their resting BP measured. Individuals with a BP >160/90 mmHg were further screened for contraindications to exercise using the ePARMed-X+ (www.eparmedx.com), all 1670 were cleared. There were no adverse events during or post exercise.

RESULTS:

The percentages of participants cleared for each BP cut-point were: <130/80 mmHg (85.3%), <140/90 mmHg (93.4%), <144/90 mmHg (94.6%), <144/94 mmHg (96.3%), <150/100 mmHg (98.6%), <160/90 mmHg (95.6%), <160/94 mmHg (97.8%) and <160/100 mmHg (99.5%). Individuals who would not have been cleared without further screening were significantly older, had a higher BMI, or had a lower maximal oxygen consumption.

CONCLUSIONS:

Conservative or lower resting BP cut-points currently applied to clear individuals for maximal exercise provide an unnecessary barrier. For individuals categorized as low-to- moderate risk by evidence-based screening tools such as the PAR-Q+ and ePARmed-X+, we recommend a resting BP cut-point of <160/94 mmHg to clear for maximal exercise until sufficient evidence is amassed to support the increase to <160/100 mmHg.

Keywords

Risk stratification adverse events blood pressure screening physically demanding occupations

1 Introduction

Best practice procedures for exercise screening in non-clinical health, wellness, commercial fitness agencies and physically demanding occupation test sites, involves the measurement of resting blood pressure (BP) in conjunction with evidence-based screening tools such as the Physical Activity Readiness Questionnaire for Everyone (PAR-Q+) and, if required, further screening through the ePARmed-X+ (www.eparmedx.com) [1]. These screening tools determine an individual’s risk stratification to be; low, moderate or high for exercise-induced adverse cardiac events before participating in maximal exercise [1]. Generally, a low or moderate risk classification combined with an appropriate resting BP is needed to clear an individual for maximal exercise. A major shortcoming of this pre-participation screening process is that non-clinical agencies apply various resting BP cut-points, some of which are based on clinical guidelines and which may or may not be appropriate for the setting, or worse, be subjectively applied to make the final exercise clearance decision. Unfortunately, these clinical guidelines often disregard and/or supersede the risk stratification. Some of these BP cut-points are excessively conservative and can unnecessarily screen individuals out of undergoing a fitness evaluation or exercise session. Further, this screening is likely to target middle-aged and/or unfit individuals who would perhaps benefit the most from exercise participation [2 –5].

Both the systolic BP (SBP) and diastolic BP (DBP) cut-points differ depending on the thresholds adopted by non-clinical agencies from a range of recommended cut-points: <130/80 mmHg [6], <140/90 mmHg [7, 8], <144/90 mmHg (www.fire-1.ca/wfxfit.html), <144/94 mmHg [9], <150/100 mmHg [10, 11], and the recently recommended evidence-based cut-point of <160/90 mmHg [12]. Our examination of the exercise clearance literature has led us to propose that DBP is the primary determinant of exercise clearance to mitigate the risk of an exercise-induced adverse cardiac event. Therefore, based on our experience we also examined the impact of two additional BP cut-points of <160/94 mmHg and <160/100 mmHg which incorporate the highest previously applied SBP and the two highest DBP values. Although many of the commonly-used BP cut-points were determined from clinical populations, they are currently also being used to screen non-clinical low-to-moderate risk populations for exercise [13, 14]. Further, the clinical cut-points for diagnosing hypertension are often inappropriately applied to clear non-clinical low-to-moderate risk individuals [15, 16] for exercise participation. However, while an individual’s measured pre-exercise BP may fall into a hypertensive classification, this is not a definitive indication that the individual has hypertension - it could simply be a reflection of the immediate circumstance [12].

In 2011, Thomas et al. published a systematic review on BP and exercise risk assessment in accord with the Appraisal of Guidelines for Research and Evaluation (AGREE) process [17] that provided evidence-based resting BP recommendations for exercise clearance [12]. Thomas et al. concluded that there is limited evidence to suggest an increased risk of exercise-induced adverse cardiac events in individuals with hypertension and found evidence for the benefits of exercise in individuals with pre-hypertensive BP, elevated normal BP or BP classed as either Stage 1 or Stage 2 hypertension. They reported that individuals with diagnosed and pharmacologically treated hypertension of <160/90 mmHg who are medically stable and have no other comorbidities should be considered low risk. However, they strongly advised against maximal exercise when individuals have a resting SBP of >200 mmHg or a resting DBP of >110 mmHg with or without comorbidities. The American College of Sports Medicine likewise designate that a resting SBP >200 mmHg or a resting DBP >110 mmHg as absolute contraindications for exercise [8, 18].

As this investigation focuses on maximal exercise, it is also important to point out the differing impact on post-exercise BP involving exercise of different intensities. Eicher et al. [4] compared the effects on post-exercise hypotension following acute low, moderate and vigorous intensity exercise on a cycle ergometer and determined that that the greatest reduction in SBP and DBP was elicited by vigorous exercise. They reported that, post exercise, for every 10% increase in the percentage of maximal oxygen consumption (% ${\dot{VO}}_{2} max$ ) there was a 1.5 mmHg reduction in resting SBP and a corresponding 0.6 mmHg reduction in resting DBP.

The objectives of the present investigation were 1) to determine the impact of applying six commonly-used and two new proposed BP cut-points on clearance rates for maximal exercise and 2) to determine the differences in clearance rates based on age, BMI classification, BP and ${\dot{VO}}_{2} max$ . The primary intended application in examining resting BP cut-points for exercise clearance was to screen participants for physical employment standards testing in emergency-related occupations such as structural firefighting, wildland firefighting, policing, correction officers and emergency nuclear power personnel. We hypothesized that the conservative or low pre-exercise BP cut-points commonly used by many non-clinical agencies to screen low-to-moderate risk individuals for maximal exercise would be unnecessarily conservative and create a barrier for many people to engage in exercise. We further hypothesized that applying these BP cut-points would screen out more low-to-moderate risk individuals who are older, have higher BMI, higher resting BP or a lower ${\dot{VO}}_{2} max$ .

2 Methods

Study participants (n = 1670) involved persons who attended our laboratory as part of a physical fitness assessment, most often in an attempt to meet the fitness qualification for physically demanding occupations.

This investigation was approved by the University Human Participants Review Committee (Approval Number e2017-048) whose research ethics guidelines are in accordance with the Canadian Tri-Council research ethics guidelines and all participants provided written informed consent prior to participation.

Shortly before their test day, participants received a reminder email with pre-test instructions including no exercising, no smoking and no caffeine use prior to taking part on the test day. Participants were screened to undergo maximal exercise by the measurement of resting BP and completion of the PAR-Q+ with follow-up queries, if necessary, using the ePARmed-X+. These evidence-based questionnaires have been validated for use across the lifespan for individuals who are apparently healthy or who have stable chronic conditions including those on medication. They are considered the best practice screening tools for fitness testing and exercise participation [19]. Most study participants were cleared for exercise based on their responses to the questions in these tools and having a resting BP <160/90 mmHg. Individuals whose BP was >160/90 mmHg (either SBP or DBP) were further reviewed by a qualified exercise professional with advanced specialized training or by a physician. As a result, all 1670 participants, regardless of their resting BP, were cleared for maximal exercise.

2.1 Measurements

Resting BP was measured by a qualified exercise professional using the automated BpTRUtrademark (BpTRU Medical Devices Ltd, Coquitlam, British Columbia, Canada) following a standardized procedure in the seated position and in a private cubicle. After a five minute sitting rest period the BpTRUtrademark recorded six sequential measurements one minute apart and generated average values for the pre-exercise SBP plus DBP using the last five of the six measurements. Any resultant values >160/90 mmHg were confirmed using auscultatory BP measurement. The BpTRUtrademark has been found to attenuate “white coat hypertension” by taking repeated measures with limited client and health care professional interaction during the measurement process [20]. To ensure accurate BP readings, the proper cuff size was chosen for each individual and all measurements were taken with the cuff placed directly on the skin of the left arm. Participants were instructed to sit quietly with the back and feet supported, with legs uncrossed and with the left arm supported at heart level throughout the BP measurements.

Participants then underwent select anthropometric measures followed by maximal exercise. Participants’ height was measured without footwear using a wall-mounted stadiometer and body mass was measured using a digital scale (Seca Alpha, Germany) while wearing light clothing and no footwear. Body Mass Index (BMI) was calculated from height and body mass (kg/m²).

During the incremental to maximal exercise oxygen consumption (VO₂) and maximal oxygen consumption (VO₂max) were determined during the final 30 seconds of each progressive workload via indirect calorimetry using a discrete component open circuit described previously [21]. The protocol consisted of 2-minute work stages that increased in intensity (treadmill speed and/or elevation) at every stage. When a participant was no longer able to continuously complete a 2 minute stage, the treadmill speed was reduced to a walking speed for 2 minutes of active recovery prior to the start of the discontinuous protocol also known as a ${\dot{VO}}_{2} max$ verification protocol [21 –25]. For the ${\dot{VO}}_{2} max$ verification, participants ran at the same speed that had been determined during the final stage of the continuous portion of the protocol with the incline raised an additional 2%. This procedure of a 2 minute active recovery and 2 minutes running for the discontinuous portion of the test was repeated until the ${\dot{VO}}_{2} max$ was verified when the participant could no longer complete a workload, or if the ${\dot{VO}}_{2}$ plateaued (within 150 mL·min^–1 of the previous workload) or decreased with the incremental verification workloads [21 –25].

Statistical analyses of the data were performed using IBM SPSS version 24 for Windows. Univariate analyses provided descriptive statistics that summarize the demographics of the study population for age, body mass, height, BMI, SBP, DBP and ${\dot{VO}}_{2} max$ . The resting BP measurements (mmHg) yielded values for SBP of $\bar{x}$ = 117.4 (SD±11.5), median = 116.0, and mode = 116.0 and for DBP $\bar{x}$ = 73.3 (SD±8.9), median = 73.0, and mode = 75.0. The BP ranged from 84–170 mmHg for SBP and 45–113 mmHg for DBP. A Shapiro-Wilk test was conducted on SBP and DBP and was found to be statistically significant (p < 0.01). The absolute skewness and kurtosis values for SBP were 0.757, SE±0.06 and 1.272, SE±0.12, respectively. The absolute skewness and kurtoisis values for DBP were.387, SE±0.06 and 0.477, SE±0.12, respectively. For large sample sizes (eg >300), absolute skewness values of <2.0 and absolute kurtosis values of <7.0 support the view of a normal distribution [26]. Normal BP values are typically clustered in a narrow distribution around 120/80 mmHg. With large sample sizes parametric procedures can be used even if statistically the data are non-normally distributed as large sample sizes tend to have a normal distribution regardless of skewing and kurtosis [26, 27]. Overall, the measures of central tendency (mean, mode and median), the histograms along with the large sample size (n = 1670) would support the assumption that the data were normally distributed within the values for both SBP and DBP. The variables assessed for each cut-point (<130/80 mmHg, <140/90 mmHg, <144/90 mmHg, <144/94 mmHg, <150/100 mmHg, <160/90 mmHg, <160/94 mmHg and <160/100 mmHg) were treated as categorical variables: sex (male vs female), age (younger <25 vs older >35), BMI (underweight or normal vs overweight, and obese), BP classification (normal vs ≥Stage 1 Hypertension), and ${\dot{VO}}_{2}$ max (lower tertile vs upper tertile). As these variables were categorical rather than continuous, and the same participants were assessed for each BP cut-point, Pearson’s Chi square analyses were performed to assess the relationship between the frequencies of those who would have been cleared for maximal exercise versus those who would not have been cleared separately for each category. Statistical analyses were not conducted between the BP cut-points and analyses were not conducted on variables in which there was a cell count of <5 for one or more cells as this provided insufficient data for meaningful analyses and interpretation.

3 Results

Descriptive statistics of the study participants are presented in Table 1. The total number of participants was 1670, comprised of 1500 males and 170 females with a combined age of 28±7 years. Based on their combined average BMI (26.5±3.5 kg/m²), the participants were collectively overweight and they had a normal resting BP (SBP 117.4±11.5 mmHg, DBP 73.3±8.9 mmHg). The average BP values of the participants at screening place them in the normal BP category and are comparable to the population BP data for Canadian adults from 2012-2015 (SBP 113 mmHg, DBP 72 mmHg) [28]. Average BP in American adults from the National Health and Nutrition Examination Survey between 2001 and 2008 would place some of the study participants into the pre- or elevated hypertension category based on their SBP (SBP 122 mmHg, DBP 71 mmHg) [15 , 29].

Table 1
Participant characteristics; 1500 Males, 170 Females (Mean±SD)

Age (years) Body Mass (kg) Height (cm) BMI (kg/m²) Resting SBP (mmHg) Resting DBP (mmHg) ${\dot{VO}}_{2}$ max (mL·kg^–1·min^–1)

Combined 28.2±6.9 85.0±13.3 178.8±7.6 26.5±3.5 117.4±11.5 73.3±8.9 50.2±7.6

Males 27.9±6.2 86.4±12.6 180.0±6.8 26.7±3.4 117.9±11.3 73.5±8.9 51.1±6.9

Females 30.3±10.6 72.5±12.6 168.3±6.5 25.5±4.0 112.6±11.9 71.7±8.8 42.5±8.8

	Age (years)	Body Mass (kg)	Height (cm)	BMI (kg/m²)	Resting SBP (mmHg)	Resting DBP (mmHg)	${\dot{VO}}_{2}$ max (mL·kg^–1·min^–1)
Combined	28.2±6.9	85.0±13.3	178.8±7.6	26.5±3.5	117.4±11.5	73.3±8.9	50.2±7.6
Males	27.9±6.2	86.4±12.6	180.0±6.8	26.7±3.4	117.9±11.3	73.5±8.9	51.1±6.9
Females	30.3±10.6	72.5±12.6	168.3±6.5	25.5±4.0	112.6±11.9	71.7±8.8	42.5±8.8

BMI (body mass index); BP (blood pressure); DBP (diastolic blood pressure); SBP (systolic blood pressure); ${\dot{VO}}_{2}$ max (maximum oxygen consumption).

A summary of the percent of participants who would have been cleared for maximal exercise by the resting BP cut-points are presented in Table 2. With all participants combined, the percent of participants who would have been cleared for maximal exercise were <130/80 mmHg (85.3%), <140/90 mmHg (93.4%), <144/90 mmHg (94.6%), <160/90 mmHg (95.6%), <144/94 mmHg (96.3%), <160/94 (97.8%), <150/100 mmHg (98.6%), and <160/100 mmHg (99.5%).

Table 2

Percent (%) who would have been cleared for maximal exercise using commonly-applied and proposed blood pressure cut-points (n = 1670). Significance of Chi square test reported for each blood pressure cut-point separately beside the percent clearance for those who would have been cleared compared with those who would not have been cleared for each variable

Variable	Commonly-Used Cut-Points (mmHg)												Proposed Cut-Points (mmHg)				Groupings for Chi square within BP Cut-Points ( p < 0.01 = significant relationship)
	<130/80 mmHg^†		<140/90 mmHg^†		<144/90 mmHg^†		<144/94 mmHg^†		<150/100 mmHg^†		<160/90 mmHg^††		< 160/94 mmHg		< 160/100 mmHg
	% Who Would Have Been Cleared
Sex
Combined (n = 1670)	85.3	p = .11	93.4	p = .65	94.6	p = .65	96.3	p = .44	98.6	***	95.6	p = .83	97.8	***	99.5	***	Males vs Females
Male (n = 1500)	84.9		93.2		94.5		96.5		98.7		95.5		97.9		99.5
Female (n = 170)	89.4		94.1		95.3		95.3		97.6		95.9		97.1		99.4
Age (years) “<25 (younger)” vs “ >35 (older)”
Combined <25 (n = 544)	93.9	p < 0.01	97.8	p < 0.01	98.3	p < 0.01	98.9	p < 0.01	99.6	***	98.7	p < 0.01	99.4	p < 0.01	99.8	***	<25 vs >35
Combined >35 (n = 206)	63.1		78.6		81.6		87.4		94.2		85.0		92.2		97.6
Males <25 (n = 482)	93.4	p < 0.01	97.7	p < 0.01	98.3	p < 0.01	99.0	p < 0.01	99.6	***	98.8	p < 0.01	99.6	***	99.8	***	Males <25 vs >35
Males >35 (n = 167)	61.1		76.0		79.0		86.2		94.6		82.6		91.0		97.6
Females <25 (n = 62)	98.4	***	98.4	***	98.4	***	98.4	***	100.0	***	98.4	***	98.4	***	100.0	***	Females <25 vs >35
Females >35 (n = 39)	71.8		89.7		92.3		92.3		92.3		94.9		97.4		97.4
BMI Classification* (kg/m²)
Underweight or Normal (n = 576)	92.7	p < 0.01	96.9	p < 0.01	97.0	p < 0.01	97.9	p < 0.01	99.1	p < 0.01	97.4	p < 0.01	98.8	p < 0.01	99.7	***	Underweight or Normal vs Overweight plus Obese
Overweight (n = 841)	85.0		93.6		94.8		96.3		98.8		96.3		97.7		99.3
Obese (n = 253)	69.6		84.2		88.1		92.9		96.4		88.9		94.9		98.0
Blood Pressure Classification**
Normal BP (n = 1558)	91.5	p < 0.01	100.0	p < 0.01	100.0	p < 0.01	100.0	***	100.0	***	100.0	***	100.0	***	100.0	***	Normal vs Stage 1 Hypertension
≥Stage 1 Hypertension (n = 112)	0.0		0.0		18.8		45.5		78.6		33.9		67.0		92.0
${\dot{VO}}_{2} max$ (mL·kg^–1·min^–1) “< lower tertile” vs “>upper tertile”
Males <48.6 (n = 461)	75.9	p < 0.01	86.8	p < 0.01	88.9	p < 0.01	93.9	p < 0.01	97.2	p < 0.01	90.5	p < 0.01	96.1	p < 0.01	98.9	***	Males Lower vs Upper Tertile
Males >54.2 (n = 464)	92.5		97.8		98.5		98.9		100.0		99.1		99.8		100.0
Females <40.9 (n = 56)	78.6	***	89.3	***	91.1	***	91.1	***	94.6	***	92.9	***	94.6	***	98.2	***	Females Lower vs Upper Tertile
Females >46.7 (n = 55)	96.4		96.4		96.4		96.4		100.0		96.4		96.4		100.0

BMI (body mass index); BP (blood pressure); SBP (systolic blood pressure); DBP (diastolic blood pressure); ${\dot{VO}}_{2}$ max (maximum oxygen consumption). ^†Opinion-Based Cut-Point; ^††Evidence Based Cut-Point; ^*BMI Classification: Underweight or Normal <25.0 kg/m²; Overweight ≥25.0 < 30.0 kg/m²; Obese >30.0 kg/m². ^**Blood Pressure Classification (mmHg): Normal (SBP <140 and DBP <90); ≥ Stage 1 (SBP ≥140 and/or DBP ≥90); ^***Statistics not reported for Chi square test if cell count was less than 5.

No significant difference was found in the percent clearance for male versus female participants. The percent clearance relative to age was examined using the two groupings of <25 years versus >35 years to differentiate the younger and older participants. For both males and females there was a lower clearance rate across all cut points for those >35 years. Chi square analysis indicated that for males there was a significantly lower clearance rate in older versus younger participants (p < 0.01).

Percent clearance based on high versus low body mass did not differ significantly. However, when the groups were differentiated based on BMI classification (29), the lowest percent clearance was in the obese category (>30.0 kg/m²), with a higher percent clearance in the overweight category (≥25.0 < 30.0 kg/m²) and the highest percent clearance in the normal plus underweight category (<25.0 kg/m²). Chi square analysis indicated a significant difference in percent clearance between the normal combined with the underweight category versus the overweight plus obese category(p < 0.01).

A significant difference was found when comparing the percent clearance of individuals with normal BP versus individuals with ≥Stage 1 hypertension (p < 0.01). As expected, those with Stage 1 hypertension or higher would have had 0% clearance when applying the more conservative BP cut-points and the highest clearance when applying more liberal BP cut-points. Individuals within the normal BP category had 100% clearance by most of the commonly-used BP cut-points and both of the proposedcut-points.

To examine percent clearance relative to ${\dot{VO}}_{2} max$ , a comparison was made between those participants who had a ${\dot{VO}}_{2} max$ in the bottom tertile of participant values and those who had a ${\dot{VO}}_{2} max$ in the top tertile of participant values. For both males and females there was a lower clearance rate across all cut points for those who had a lower ${\dot{VO}}_{2} max$ . Chi square analysis indicated that for males, at all cut points there was a significantly lower clearance rates in those participants who had a lower ${\dot{VO}}_{2} max$ (p < 0.01).

4 Discussion

The purpose of this study was to examine the impact of applying six commonly-used and two proposed resting BP cut-points to clear individuals for maximal exercise. The findings support our hypothesis that the resting BP cut-points that are commonly used to screen individuals are unnecessarily conservative and would create a barrier for many people to engage in maximal exercise. The findings from this study also support our hypothesis that there would be a lower percent clearance for those individuals who were older, had higher BMI, higher resting BP and lower ${\dot{VO}}_{2} max$ even though they were classed as low or intermediate risk. When the more conservative BP cut-points are applied in community centres and fitness facilities at which there are not likely to be either qualified exercise professionals with advanced training or physicians to provide follow-up clearance, a barrier would be created for many individuals to engage in maximal exercise.

While lower intensity exercise has many benefits, there are additional benefits that can best be achieved from participation in higher exercise intensities. Individuals with higher resting BP or a family history of hypertension (diagnosed or undiagnosed) should regularly participate in vigorous exercise to achieve the greater benefits [4 , 30]. For low-to-moderate risk applicants and incumbents in emergency-related physically demanding occupations who are required to have their resting BP measured during the job application screening process or their annual job physical fitness re-evaluation the more conservative BP cut-points create a significant and unnecessary operational barrier.

It is important to note when examining the progression in clearance rates across the various cut-points that SBP increases considerably without impacting exercise clearance, while small changes in DBP have significant effects. That is, the primary determinant of clearance is the DBP rather than the SBP. This is perhaps related to the tight regulation of DBP during exercise. It is important to keep in mind that BP clearance cut-points are used because of the supposed link between BP and possible exercise-induced adverse cardiac events. Unlike SBP, which appears to be unrestrained and often exceeds 200 mmHg during heavy exercise to maintain perfusion of the heavily contracting muscles, DBP generally decreases or increases by only 10 mmHg [31]. This means that venous return must be markedly enhanced during maximum exercise and underscores why decreased total peripheral resistance and enhanced diastolic filling rate are critical responses to whole body dynamic exercise [21, 31].

To our knowledge, this is the first non-clinical study to compare exercise clearance rates when applying various BP cut-points in screening for maximal exercise. We examined a large number of participants which included individuals of various ages and participants of varying degrees of aerobic fitness and BMI status, whose BP profile was similar to the BP profile of the Canadian and American populations. It is important to re-state that when the resting or pre-exercise BP of a participant was above our normally applied cut-point of <160/90 mmHg, in all cases they were further screened either by a qualified exercise professional with advanced specialized training or by a physician and all were subsequently cleared for maximal exercise which they then completed with no adverse cardiac events.

In light of the present findings and after re-visiting the findings of Thomas et al. [12], the authors of this article who participated in and chaired the associated AGREE process recommend that the standard resting BP cut-point for exercise clearance be revised to <160/94 mmHg. In addition, we recommend that research be continued to examine the possibility of an even higher cut-point of <160/100 mmHg as the standard for exercise clearance for persons classed as low or moderate risk. Given that there were no adverse events while participating in or following maximal exercise for persons in the present investigation who had a BP of <160/100 mmHg (as well as a small number of individuals whose resting BP was >160/100 mmHg), we expect that continuing research will support the use of a resting BP of <160/100 mmHg as the standard cut-point for exercise clearance.

Henceforth, in our laboratory we will apply <160/94 mmHg as the standard cut-point, and persons who have a BP of <160/100 mmHg and are categorized as low to moderate risk by the PAR-Q+/ePARmed-X+ will receive additional screening for exercise clearance by a qualified exercise professional with advanced specialized training or by a physician. The additional screening will give specific consideration to the PAR-Q+ and ePARmed-X+ responses, and persons with a BP <160/100 mmHg who are cleared will receive particular attention while exercising.

We recognize that there is a risk of sudden death during maximal exercise participation or maximal exercise testing; 1.4 non-fatal events per 10,000 tests and 0.2 to 0.8 fatal events per 10,000 tests or 1 per 10,000 hours of testing [32, 33], with this same potential risk when exercising in our laboratory. However, this risk is mitigated in our laboratory as the participants are under the continuous supervision of qualified exercise professionals who are trained in both CPR and use of an on-site automated defibrillator.

There were noteworthy limitations to this study. The effect of “white coat hypertension” on a participant’s resting BP was potentially minimized through the use of an automated BP monitor and an average measurement of the readings. However, there is still the possibility that some participants’ resting BP was artificially high due to the fact that it was tested in a laboratory setting. As well, the BP readings were taken in the morning which may have led to different results if it was tested at a different time of day. Other potential limitations to this study were that there were considerably fewer participants who were above the highest BP cut-points and the participants were predominantly male.

5 Conclusions

The findings of this study support the adoption of a resting or pre-exercise BP cut-point of <160/94 mmHg for maximal exercise clearance when persons are classified as low-to-moderate risk using evidence-based screening tools such as the PAR-Q+ and ePARmed-X+. This new cut-point will reduce the barrier commonly encountered when applying the more conservative BP cut-points. As well, these conservative cut-points would have screened out a greater portion of those persons who are at risk for hypertension due to increased age, high BMI and low ${\dot{VO}}_{2} max$ , when these individuals would benefit the most from habitual exercise. As well, for low-to-moderate risk applicants and incumbents in emergency-related physically demanding occupations (structural firefighters, wild land firefighters, paramedics, police, correctional officers, emergency nuclear power personnel, etc.) who are required to have their resting BP measured during the job application process or annual fitness re-evaluation, the more conservative BP cut-points used by many agencies create a significant operational barrier. Further, we speculate that our future research will support the use of a resting BP of <160/100 mmHg as the cut-point for exercise clearance at all intensities.

Conflict of interest

The authors declare no conflicts of interest for this study. We declare that the results of the study as presented clearly, honestly and without fabrication, falsification or inappropriate data manipulation.

References

Warburton

DER

, Gledhill

, Jamnik

VKJ

, Bredin

SSD

, McKenzie

, Stone

, Charlesworth

, Shephard

. Evidence-based risk assessment and recommendations for physical activity clearance: Consensus Document 2011. Appl Physiol Nutri Metab. 2011;36:S266–98. doi:10.1139/H11-062 .

Warburton

DER

, Nicol

, Bredin

SSD

. Health benefits of physical activity: The evidence. Can Med Assoc J. 2006;174(6):801–9.

Harris

, Watson

, Carlson

, Fulton

, Dorn

, Elam-Evans

. Adult participation in aerobic and muscle-strengthening physical activities – united states, 2011. Morb Mortal Wkly Rep. 2013;62(17):326–30.

Eicher

, Maresh

, Tsongalis

, Thompson

, Pescatello

. The additive blood pressure lowering effects of exercise intensity on post-exercise hypotension. Am Heart J. 2010;160(3):513–20.

Ghadieh

, Saab

. Evidence for exercise training in the management of hypertension in adults. Can Fam Physician. 2015;61:233–9.

Canadian Diabetes Association. Clinical Practice Guidelines. Can J Diabetes. 2013;37:212.

Balady

, Chaitman

, Driscoll

, et al.Recommendations for cardiovascular screening, staffing, and emergency policies at health/fitness facilities. Circulation. 1998;30(6):1009–18.

Pescatello

, Arena

, Riebe

, Thompson

. ACSM’s guidelines for exercise testing and prescription. 9th ed. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins Health; 2014, p. 456.

anadian Society for Exercise Physiology CSEP- PATH: Physician Physical Activity Readiness Clearance [Internet]. Available from http://www.cseca/cmfiles/publications/parq/physician%20clearance%20form%20csep-cpt.pdf.

10.

Director General Personal Family Support Services Directorate of Fitness. Canadian Forces EXPRES Operations Manual National [Internet]. 5th ed. 2012[cited 2018 Feb 4]. 22 p. Available from:https://www.cfmws.com/en/AboutUs/PSP/DFIT/Fitness/Correspondence/Documents/CF%20EXPRES/CF%20Expres%20Manual_Eng_July_FINAL_2012.pdf.

11.

Jette

, Landry

, Sidney

. Blood pressure response to the canadian aerobic fitness test. Can J Public Heal. 1991;82(4):267–76.

12.

Thomas

, Goodman

, Burr

. Evidence-based risk assessment and recommendations for physical activity clearance: Established cardiovascular disease. Appl Physiol Nutr Metab. 2011;36(Suppl 1):S190–213.

13.

World Health Organization. Blood pressure targets and the WHO/ISH guidelines. Rev Prescrire. 2005;25(261):394–5.

14.

World Health Organization. A global brief on Hypertension- Silent killer, global public health crisis. Geneva: World Health Organization; 2013, pp. 1–40. (WHO publication; no. WHO/DCO/WHD/2013.2).

15.

Leung

, Daskalopoulou

, Dasgupta

, McBrien

, Butalia

, Zarnke

, et al.Hypertension canada’s 2017 guidelines for diagnosis, risk assessment, prevention, and treatment of hypertension in adults. Can J Cardiol. 2017;33(5):557–76.

16.

Whelton

, Carey

, Aronow

, Casey Jr

, Collins

, Dennison Himmelfarb

, DePalma

, Gidding

, Jamerson

, Jones

, MacLaughlin

, Muntner

, Ovbiagele

, Smith Jr SC , Spencer

, Stafford

, Taler

, Thomas

, Williams

Sr KA

, Williamson

, Wright Jr

, 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation and management of high blood pressure in adults. Journal of the American College of Cardiology. 2017. doi:10.1016/j.jacc.2017.11.006 .

17.

The AGREE Collaboration. Development and validation of an international appraisal instrument for assessing the quality of clinical practice guidelines: The AGREE project. Qual Saf Health Care. 2003;12(1):18–23.

18.

Gordon

. Hypertension In: Durstine

, Moore

, Painter

, Roberts

, editors. Exercise management for persons with chronic diseases and disabilities. 3rd ed. Champaign: Human Kinetics; 2003, pp. 107–13.

19.

Bredin

SSD

, Gledhill

, Jamnik

, Warburton

DER

. PAR-Q+ and ePARmed-X+: New risk stratification and physical activity clearance strategy for physicians and patients alike. Can Fam Physician. 2013;59(3):273–7.

20.

Edwards

, Hiremath

, Gupta

, McCormick

, Ruzicka

. BpTRUth: Do automated blood pressure monitors outperform mercury? J Am Soc Hypertens. 2013;7(6):448–53.

21.

Gledhill

, Cox

, Jamnik

. Endurance athletes’ stroke volume does not plateau: Major advantage is diastolic function. Med Sci Sports Exerc. 1994;26(9):1116–21.

22.

Thoden

. Physiological testing of the high-performance athlete. Editors: MacDougall

, Wenger

, Green

. Champaign, Illinois, Human Kinetics2nd Edition. 1991, Chapter 4, pp. 107–170.

23.

Beltz

, Gibson

, Janot

, Kravitz

, Mermier

, Dalleck

. Graded exercise testing protocols for the determination of VO₂max: Historical perspectives, progress, and future considerations. J Sports Med. 2016;2016:1–12.

24.

Poole

, Jones

. Measurement of the maximum oxygen uptake VO₂max: VO₂peak is no longer acceptable. J App Physiol. 2017;122(4):997–1002.

25.

Howley

, Bassett

, Welch

. Criteria for maximal oxygen uptake: Review and commentary. Med Sci Sports Exerc. 1995;27(9):1292–301.

26.

Kim

H-Y

. Statistical notes for clinical researchers: Assessing normal distribution (2) using skeweness and kurtosis. RDE. 2013. https://doi.org/10.5395/rde.2013.38.1.52.

27.

Ghasemi

, Zahediasl

. Normality tests for statistical analysis, A guide for non-statisticians. Int J Endocrinol Metab. 2012;10(2):486–9.

28.

Statistics Canada. Blood pressure of adults, 2012 to 2015 Health Fact Sheets Page [Internet]. Ottawa: Statistics Canada, Health Statistics Division; 2016Oct 13 [updated 2016 Oct 13; cited 2017 Jul 14]. Available from:. http://www.statcan.gc.ca/pub/82-625-x/2016001/article/14657-eng.htm.

29.

Wright

, Hughes

, Ostchega

, Yoon

, Nwankwo

. Mean systolic and diastolic blood pressure in adults aged 18 and over in the United States, 2001-2008. Natl Health Stat Report. 2011;35:1–24.

30.

Ramirez-Jimenez

, Morales-Palomo

, Pallares

, Mora-Rodriguez

, Ortega

. Ambulatory blood pressure response to a bout of HIIT in metabolic syndrome patients. Eur J Appl Physiol. 2017;117(7):1403–11.

31.

Sharman

, LaGerche

. Exercise blood pressure: Clinical relevance and correct measurement. J Hum Hypertens. 2015;29(6):351–8.

32.

Goodman

, Thomas

, Burr

. Evidence-based risk assessment and recommendations for exercise testing and physical activity clearance in apparently healthy individuals. Appl Physiol Nutr Metab. 2011;36(Suppl 1):S14–32.

33.

Warburton

DER

, Taunton

, Bredin

SSD

, Isserow

. The risk-benefit paradox of exercise. British Columbia Medical Journal. 2016;58(4):p210–8.