It is widely accepted that cardiovascular disease (CVD) is the leading cause of death in developed countries 1 . Over the past decade it has become recognised that physical activity is an independent factor in the determination of over all CVD risk through the prevention of atherosclerosis and reduction of thrombotic risk 2 3 . Evidence supports an inverse association between physical fitness and various CVD risk factors, including glucose tolerance 4 , cholesterol 5 , blood pressure 6 , resting pulse rate 7 and obesity 8 , and markers of systemic inflammation including C-reactive protein (CRP) 9 , and TNFα 10 . It is suggested that such effects occur through a reduction in lipoprotein oxidation 11 , improved endothelial function via the increased production of nitric oxide and prostacyclin 12 , decreased atherogenic activity of blood mononuclear cells effecting the production of cytokines 13 , and a reduced accumulation of collagen in the arterial wall 14 . Therefore guidelines recommend that individuals accrue 30 minutes of moderate physical activity on at least 5 days of the week 15 16 .

Despite the positive impact of physical fitness on CVD, developed societies have become more sedentary in both occupation and leisure time. A recent observational study of 2595 civil servants in Northern Ireland reported that almost two thirds failed to engage in regular, moderate physical activity, with females twice as likely to abstain from exercise than men 17 . In England it has been reported that a total of 24.2% of men and 19.8% of women meet the activity recommendations; a total that dropped to 17.6% and 13.0% when domestic activity was excluded 18 . Since most adults will spend more than half their waking hours within the workplace, worksite health promotion programs that influence employee behaviour by promoting physical activity could prove fundamental in addressing the growing problem of sedentary habit and cardiovascular risk.

A number of randomised-controlled trials assessing the benefit of workplace exercise interventions on health-related outcome measures (body composition, blood pressure, lipid profile, inflammatory markers) have been reported 19 20 21 . However, the conclusions from these trials have been based upon the subjective self-report of physical activity, without individualised prescription or monitoring of the exercise programme, and objective assessment. Therefore the relationship between improved physical capacity and health from workplace exercise remains inconclusive 21 . In view of this there is a necessity for further studies of strong methodological quality to examine corporate exercise strategies adaptable to occupational time constraints.

The aim of this pilot study was to investigate the efficacy of a structured, monitored 12-week aerobic exercise training intervention programme on modifying the cardiovascular risk profile of a sedentary National Health Service (NHS) workforce, and to evaluate whether it could be implemented during working hours.

The data from the study confirmed that a moderate intensity aerobic exercise-training programme performed 4 times a week could be successfully implemented within the workplace during working hours. Furthermore, it was demonstrated that it was effective at reducing risk factors associated with cardiovascular disease, and at improving physiological capacity within previously sedentary individuals. Specifically, significant improvements were found in peak oxygen consumption (VO_{2 peak}), economy of absolute oxygen utilization at both 2 minutes (2minVO₂) and 4 minutes (4minVO₂), and C-reactive protein (CRP) concentration. These results confirm previous reports showing that improved cardiovascular fitness, or physical activity level reduces cardiovascular risk, with a particular association with lower CRP levels 9 23 24 . This is the first report combining objective physiological outcome measures with objective monitoring of the training programme to demonstrate the type of exercise that can be effectively carried out during working hours, while still providing health related benefits.

At the end of the 8-week intervention period absolute VO_{2 peak} increased significantly by 5 % in the exercise group, while it decreased significantly by 6 % in the control group. There was no significant change in peak heart rate in the exercise group, but there was a significant reduction in peak heart rate in the control group, suggesting that a decline in effort contributed to the observed fall in VO_{2 peak}. Absolute 2minVO₂ and 4minVO₂ decreased significantly by 17 % and 11 % respectively in the exercise group, while there was no significant change in the control group. Furthermore, as the exercise group averaged the completion of 81 % and 84 % of the prescribed exercise sessions between week 1 and week 4, and week 4 and week 8 respectively, it can be concluded that the progressive aerobic exercise training programme was not only effective at improving the physical fitness of a sedentary group of adults, but was also successful at increasing physical activity levels.

However although cardiovascular fitness and physical activity are positively related, research indicates that it is the former that is more closely linked to cardiovascular disease risk factors and disease, than actual physical activity level 25 26 . As a consequence it has been shown that it is only those individuals who increase their VO_{2 max}, rather than their actual physical activity level that reduce their relative risk of cardiovascular disease risk factors 27 . This has been attributed to a reduction in large artery stiffness, which may be mediated by concomitant changes in high-density lipoprotein (HDL) cholesterol and body weight 28 .

This holds relevance for the present study: after 8 weeks when the exercise group were not provided with any further progression or instruction to the exercise training programme VO_{2 peak} decreased by 2 %. In view of the 70 % completion of the 16 sessions, and the significant improvement in absolute 4minVO₂ (-7 %), it appears probable that the intensity of the exercise performed within this time period was too low to challenge VO_{2 peak}. This is supported by evidence that indicates that VO_{2 max} has a modest association with physical activity, but a much stronger association with the mean intensity of the exercise 29 . In view of this, and the cardio protective benefit of an increase in VO_{2 max} future research should evaluate the implication of a higher intensity workplace exercise training programme on the modification of cardiovascular risk profile, while assessing whether it remains successful at ensuring exercise adherence.

It appears that supervision and progression of the exercise programme may influence adherence 30 31 . In the present study, at 8 weeks when no further progression or supervision to the exercise training programme was provided a reduction in the adherence of the training sessions occurred; 81 % and 84 % were completed in week 1 to week 4 and week 4 to week 8, while only 70 % were completed in week 8 to week 12. This could further highlight the need for employers to ensure the provision of additional support and progression to the original training programme for optimal participation of employees, and success of the programme.

The exercise group demonstrated a significant decrease in CRP of -0.4 ± 0.6 mg/L between week 1 and week 4, and -1.0 ± 0.4 mg/L between week 4 and week 8. However while this is in accordance with previous research 24 32 , it should be noted that due to a mean baseline value indicating high risk for CVD (> 3.0 mg/L), that the reduction would still result in a mean value indicating average risk of CVD (2.2 mg/L) 33 . The mechanism behind such action remains unclear. It has been postulated that a reduction in CRP is attained via the positive benefit of exercise on BMI via modulation of the percentage of visceral fat and insulin receptor sensitivity 24 . However, within the present study there was no such positive effect on body composition, or fasting glucose. Another potential explanation is that among unfit individuals there is a greater generation of reactive oxygen species via normal metabolic processes, and unaccustomed muscle stretching. This leads to subliminal injury of the myocytes, that causes both cell and tissue oxidative damage, leading to an inflammatory response 34 . Evidence confirms that chronic exercise induces a mechanical resistance of the myocytes to stretching, and elevates endogenous antioxidant enzyme activity, which prevents excessive local inflammatory response 35 . As there were significant gains in aerobic capacity within the exercise group it is plausible that this explanation provides a mechanism of action for the observed results.

No significant change was observed in IL-6 at any time point during the study. However there was a significant reduction in TNF-α between week 1 and week 4 in the exercise group. As TNF-α directly impairs glucose uptake and metabolism via a direct effect on insulin signal transduction, a reduction holds positive benefit for prevention of CVD 10 . Thus despite the lack of a significant change in fasting glucose, there is still suggestive evidence that the training programme may accrue positive benefit for this specific risk factor.

Although the present study was successful at improving maximal and submaximal aerobic exercise capacity, it had no significant effect on fasting glucose or cholesterol, blood pressure or BMI. It is likely that the small sample size is responsible for such null findings. However it is also unsurprising for a number of reasons.

Firstly, although physical activity and exercise improves insulin sensitivity through a direct effect on the muscle (enhancement of insulin receptor autophsophorylation 36 , increase in GLUT-4 content 37 and glucose transport-phosphorylation 38 , and a reduction in visceral obesity 39 , neither the exercise nor the control group exhibited impaired glucose tolerance (exercise = 5.04 ± 0.50; control = 5.11 ± 0.52 mmol/L) at baseline that would have required intervention modification. The same can be said for blood pressure, with all participants classified as normotensive (exercise = 118 ± 12/73 ± 10; control = 106 ± 10/69 ± 9) at baseline. Nevertheless, in view of the beneficial effect that exercise has on glucose tolerance, and evidence that those with low levels of physical fitness are shown to be at a relative risk of 1.52 for developing hypertension, when compared to highly fit individuals 6 , the use of exercise in aiding glycemic control, and the maintenance of healthy blood pressure should still be encouraged.

Secondly, regarding BMI, it should be considered that the aim of the training programme was not to directly target weight loss for a reduction of cardiovascular risk, but instead to improve physiological capacity, and biomarkers of cardiovascular profile. In accordance with this, and in the absence of dietary modification, it would have been unlikely that the 4 × 30 minute sessions per week would have provided the necessary negative energy balance stimulus of 500 – 1000 kcal·d^-1 to achieve gradual weight loss (ACSM, 2006). Given that a BMI ≥ 30 kg·m^-2classifies obesity, concomitantly increasing the risk of hypertension, poor total cholesterol/HDL cholesterol ratio, coronary disease and mortality rate 40 , there is a need for future work place health promotion programmes to evaluate whether an aerobic exercise training programme specifically targeting weight loss and management as its primary outcome can be successfully implemented within the workforce.

A limitation of the present study was the failure to examine lipoprotein subfractions; small low-density lipoproteins (LDLs), high-density lipoproteins (HDLs), high-density lipoprotein subfractions (HDL₃ and HDL₂), very low-density lipoproteins (VLDLs), and respective particle size, that better reflect CVD risk than absolute measures of cholesterol concentrations 41 . In a recent study, Halverstadt et al (2007) concluded that an aerobic exercise training program consisting of 20 minutes, 3 days a week, progressively building up to a duration of 40 minutes and an intensity of 70 % VO_{2 max} for a period of 24 weeks, plus a weekend walk was successful at improving lipid subfraction profile and cardiovascular risk independent of diet and change in body fat. This is supported by several other studies, which also indicate an improved plasma lipoprotein profile with exercise training, exclusive of weight loss 5 42 .

Our pilot study provides objective and randomised controlled trial data demonstrating that regular supervised exercise increases physical activity for healthy individuals, and improves exercise capacity, with a concomitant cardioprotective benefit. As this can be achieved without disrupting the working day, this exercise programme provides a means of improving health at work. As the study was conducted within an NHS department, it may be of particular relevance to the NHS, as the single largest employer in Europe.

The author(s) declare that they have no competing interests.

JAH conceived the study design, carried out the testing, performed statistical testing and drafted the manuscript. MM carried out the immunoassays. GPW participated in the coordination of the study and drafting of the manuscript. KvS helped to draft the manuscript. TSL conceived of the study, and participated in its design and coordination, and helped to draft the manuscript. All authors read and approved the final manuscript.