By LANCE C. DALLECK, PH.D.
Substantial public-health efforts have recently been aimed at promoting and increasing levels of physical activity. The good news is that these efforts appear to be having some effect, as the prevalence of sedentary behavior has begun to decline. Unfortunately, levels of physical inactivity are still too high. One major area of concern is that long-term maintenance of regular exercise remains poor, with attrition rates for structured exercise programs ranging from 9 percent to 87 percent. Simply put, many people are able to successfully initiate an exercise program, but fail to adhere to regular exercise throughout their lives.
Nevertheless, there are numerous strategies you can use with your clients to enhance exercise adherence, such as identifying individualized, attainable goals and objectives for exercise. However, implementation of this practical recommendation requires a clear understanding of the likely—and realistic—improvements in cardiorespiratory fitness and various disease-risk factors that can be expected over a given period of training. If the primary goals of a client are to modify his or her lipid profile and improve cardiorespiratory fitness, you need to convey how much these parameters are realistically going to change in the coming months. Without this knowledge, attainable goals for the exercise program cannot be established and it is highly probable that your client will become predictably disenchanted with the program when he or she falls short of lofty goals. What follows is an evidence-based guide on the typical improvements in cardiorespiratory fitness and common disease-risk factors that can be expected from regular participation in an exercise program, and the duration of training ordinarily required to elicit these changes, all of which can help you better manage your clients' expectations and help them stick with their recommended programs.
An initial and considerable challenge facing personal trainers at the beginning of a partnership with new clients is to assist them in successfully prioritizing the goals for the exercise program. Simply put, what should the primary objectives of an exercise program be for most clients? Undoubtedly, every client will have different reasons for becoming more active. However, because cardiovascular disease (CVD) has been the most pressing health problem in the United States for the last century, it is logical that many adults engage in exercise programs aimed at reducing the risk of CVD development and CVD mortality. To accomplish this goal, it is paramount that the risk factors that contribute to the process of CVD development and mortality are positively modified.
CVD Risk Factors and Exercise: How Much Improvement Is Expected and How Long Will it Take?
Major risk factors for CVD include low levels of cardiorespiratory fitness, dyslipidemia (e.g., elevated LDL cholesterol and low HDL cholesterol levels), hypertension, type 2 diabetes and obesity (Blair, 2009). As a fitness professional, you should strive to acquire baseline measurements of all these parameters for every client. Subsequently, the obtained values can be evaluated to determine if the client is in an elevated risk category. If so, positive changes to those specific risk factors should be a primary program objective. While this may sound simple on paper, it is essential that clients understand how much progress they can expect to make on each of their goals, and how much time they will likely need to accomplish the task. Let’s turn our attention to answering these critical questions.
Cardiorespiratory fitness has been called the ultimate health outcome (Franklin, 2007). After all, low cardiorespiratory fitness has been shown to account for more deaths in both men and women than any other CVD risk factor (Blair, 2009). The good news is that low cardiorespiratory fitness is exceptionally modifiable. In fact, improvements in fitness will likely be more pronounced when compared to other risk factors. Research indicates that an individual can typically expect to improve his or her cardiorespiratory fitness by 10 percent to 30 percent after three months of aerobic training. These changes pay big dividends with regard to long-term health, as the literature suggests that a 10-percent improvement in cardiorespiratory fitness can bring about a 15-percent reduction in mortality (Dunn et al., 1999).
According to one study, hypertension is responsible for the second highest number of overall deaths among American adults (Blair, 2009). Research has shown an inverse relationship between exercise and blood pressure levels. Accordingly, it is to be expected that engaging in a regular exercise program will help reduce blood pressure levels. A single, acute bout of moderate-intensity exercise can lower systolic blood pressure by 5 to 7 mmHg for up to 22 hours following the completion of the exercise session (ACSM, 2004). Interestingly, the chronic benefits from exercise training in terms of blood-pressure reduction are less pronounced, with the literature reporting a decrease of 3 mmHg and 2 mmHg in systolic and diastolic blood pressure, respectively, after anywhere between one to six months of aerobic training (Fagard, 2006). Although these changes appear rather minimal, it has been demonstrated that blood-pressure reductions of as little as 2 mmHg are associated with a 6-percent decrease in stroke mortality and a 4-percent decrease in coronary artery disease (Chobanian et al., 2003).
The number one goal for many clients initiating an exercise program is to lose weight. Given both the widespread prevalence of obesity and the fact that excessive fat mass is associated with a myriad of unhealthy conditions, this is an admirable target. Regrettably, clients frequently establish weight-loss goals that are incongruent with what the scientific literature suggests are likely to occur with exercise training. Comprehensive reviews of studies examining the relationship between exercise and weight loss report weight reductions of approximately 1 to 3 pounds with four months of training (Macfarlane and Thomas, 2010). However, it is of absolute importance that you explain to your clients that these relatively modest changes confer important overall health benefits. A number of studies have linked substantial improvements to various chronic disease risk factors, including low cardiorespiratory fitness, insulin resistance and low HDL cholesterol, with weight-loss reductions of only 2 percent to 3 percent (Donnelly et al., 2009).
Type 2 Diabetes
Type 2 diabetes is currently an epidemic that is projected to worsen; it has been estimated that one in three Americans born in 2000 or later will develop type 2 diabetes in their lifetime (ACSM, 2010). This is particularly worrisome given that heart disease death rates are two to four times higher in those with type 2 diabetes compared to those without the metabolic condition (Roger et al., 2011). However, individuals with type 2 diabetes who exercise regularly are likely to experience numerous benefits, including increased insulin sensitivity, decreased hemoglobin A1C (HbA1C) and reduced insulin requirements. Chronic aerobic training over two to 12 months has been reported to decrease HbA1C levels by 0.6 percent (Chudyk and Petrella, 2011). This reduction is clinically significant for individuals with type 2 diabetes and has been linked with a 22-percent reduction in microvascular complications and an 8-percent reduction in the rate of myocardial infarctions. In nondiabetics, regular exercise also provides important benefits in terms of maintaining normal insulin sensitivity and blood glucose control. For example, it has been reported that two months of aerobic exercise training reduces fasting blood glucose levels by 6 mg/dL (Hasbum et al., 2006).
Dyslipidemia refers to abnormalities in the blood lipid and lipoprotein profile, and is characterized by elevations in total cholesterol, LDL cholesterol and triglycerides, along with low HDL cholesterol. These parameters may be modified with regular exercise. Three months of aerobic training has been shown to increase HDL cholesterol 2 to 8 mg/dL (Durstine et al., 2001). Likewise, regular exercise over similar time periods results in LDL-cholesterol reductions between 3 percent and 10 percent (Tambalis et al., 2009; Kelley, Kelley and Tran, 2004). Total cholesterol and triglycerides can also be attenuated following several months of regular exercise; typical decreases in total cholesterol are 4 percent to 20 percent, while triglycerides are lowered by 5 to 38 mg/dL (Durstine et al., 2001). These positive modifications to the lipid profile yield important overall health benefits. It has been estimated that for every 1 mg/dL increase in HDL cholesterol, the risk of a coronary heart disease (CHD) event is reduced by 2 percent to 3 percent (Pasternak, 1990). Moreover, it has been purported that for every 1 percent decrease in LDL cholesterol, there is a corresponding 1 percent reduction in risk for significant heart disease events (NCEP ATP III, 2002). Similarly, each 1 percent reduction in total cholesterol levels has been associated with a 2 percent decrease in CVD rate (Neaton & Wentworth, 1992). Research suggests that the above-mentioned modifications are most likely to be seen in HDL and triglycerides, while the adaptations in total cholesterol and LDL cholesterol are not as universal.
Exceptions to the Rules
This article has focused on the average expected changes to key health outcomes based on current research. It is important to note that the very same studies have also reported that improvements across all health outcomes examined might, in some instances, be more pronounced for certain individuals. A main objective of this article is for you to understand and appreciate the changes likely to occur following training in a typical client (summarized in Table 1). However, these facts should not be perceived as an artificial ceiling on training adaptations. Doing so could inadvertently superimpose limitations on exercise program goals. Ultimately, it is a careful balance of blending the probable reality with cautious optimism that will most benefit your clients.
|Table 1. The Expected Change, Timeline and Meaningfulness for Key Health Outcomes
||10% ↑ VO2max = 15% ↓ risk of mortality
|Systolic Blood Pressure
||↓ 3 mmHg
||2mmHg ↓ SBP = 6% ↓ stroke mortality and 4% ↓ CHD
|Diastolic Blood Pressure
||↓ 2 mmHg
||No data available
||↓ 1–3 lb
2–3% ↓ weight = improvements in other risk factors
|Fasting Blood Glucose
||↓ 6 mg/dL
||No data available
||0.6% ↓ HbA1C = 22% ↓ microvascular complications and 8% reduced rate of MI
||1% ↓ TC = 2% ↓ CVD rates
1% ↓ LDL = 1% ↓ risk of CHD event
||↑ 2–8 mg/dL
||1mg/dL ↑ HDL = 2–3% ↓ risk of CHD event
||↓ 5–8 mg/dL
||No data available
It also is important to understand that, in most instances, the outcomes reported in Table 1 are what one might expect to see after three to six months of training. In reality, this is a very short timeframe. It might be more appropriate to consider what adaptations will likely occur if training continues on a more long-term basis (e.g., two or three years). Unfortunately, there is virtually no evidence from randomized, controlled trials to adequately predict what long-term changes might occur due to exercise alone. Nonetheless, the results from cross-sectional studies permits insight into the training outcomes possible when exercise is performed long-term. For instance, it has been reported that HDL-cholesterol levels in trained individuals are nearly 20 points higher than in their sedentary counterparts. Clearly, the magnitude of differences in HDL between these groups is substantially greater than the 2 to 8 mg/dL figure reported in Table 1 for expected changes. This suggests that beneficial training adaptations continue to accrue for HDL well beyond the first three to six months of training. Certainly, this same principle holds true for all health outcomes examined in this article.
Finally, an awareness of the physiological aspects of aging will assist you in establishing realistic program goals for your clients. Previously sedentary older adults initiating an exercise program can expect improvements in numerous health benefits. However, because of the natural decline in function associated with aging, maintenance of function must be considered to be a successful outcome. For example, research suggests that cardiorespiratory fitness decreases, on average, by 1 percent per year (Dempsey and Seals, 1995). If you were to work with a client for three years and observe no change in his or her cardiorespiratory fitness level over that time, you may rightly conclude that you had designed and implemented an effective program. Why? The inevitable decline in physiological function, in this case cardiorespiratory fitness, has been delayed. In other words, maintenance can also be perceived as a triumphant outcome.
What Is the Collective Meaningfulness of These Changes?
The expected change and associated meaningfulness for each individual health outcome is presented in Table 1. However, it is entirely possible that a client may be interested in beginning an exercise program in an effort to modify several CVD risk factors simultaneously. Let’s discuss how to quantify the collective meaningfulness of the expected changes for this scenario. First, we need to introduce an instrument known as the Framingham 10-year risk calculator, which can be found at the American Heart Association Web site. The tool produces an estimate of an individual’s 10-year risk for a cardiac event or heart disease mortality. This calculation is based on personal characteristics, such as age and gender, along with various risk-factor values. The tool bases its calculations on a scoring system, which was developed with data collected from the Framingham Heart Study. Given that mortality from CVD is the leading cause of death among Americans, acquiring an estimate of a client’s CVD risk can provide you with valuable information. In particular, establishing a CVD risk estimate at baseline can serve as a reference from which future CVD risk estimates may be compared following exercise training. Consider the following example:
Sienna, a sedentary grandmother of two, has come to your facility to initiate an exercise program. Some of her personal information and baseline values for CVD risk factors are listed in Table 2. According to this preliminary information, Sienna’s risk for a heart attack or dying from heart disease over the next 10-year period is estimated at 6 percent. Subsequently, you diligently work with Sienna over the next six months, during which she regularly visits your facility and closely adheres to the exercise program you have designed. It is clear at her next medical checkup that the exercise has been beneficial. There are positive modifications to each of her health outcomes. It should also be noted that these improvements are consistent with the likely changes we would expect with six months of exercise training. To determine the collective meaningfulness of these changes you recalculate her 10-year risk estimate for a heart attack or mortality from heart disease and find that it has been cut in half, from 6 percent to 3 percent.
|Table 2. Example of Individual 10-year Risk for Cardiac Event or Heart-disease Mortality, Before and After Exercise Training
|Body Mass (lb)
|Systolic Blood Pressure
|Diastolic Blood Pressure
|Total Cholesterol (mg/dL)
|LDL Cholesterol (mg/dL)
|HDL Cholesterol (mg/dL)
|Fasting Blood Glucose (mg/dL)
|10-year Risk of Cardiac Event
The Take-home Message
All clients initiating an exercise program should have great expectations. However, it is paramount that you assist your clients with establishing attainable goals. Understanding the expected change in key health outcomes, as well as the expected timeframe to achieve these adaptations, will result in the most realistic and triumphant result.
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Lance C. Dalleck, Ph.D., is academic coordinator of the Cardiac Rehabilitation postgraduate program at the University of Auckland in New Zealand. His research interests include improving exercise performance and health outcomes through evidence-based practice, quantifying the energy expenditure of outdoor and non-traditional types of physical activity, and studying historical perspectives in health, fitness and exercise physiology.