Resilient Female Hormone Function after Record-Breaking Antarctic Crossing!

Women are thought to be biologically sensitive to effects of extreme physical activity when accompanied by weight loss–possible negative consequences cited include bone fractures and fertility difficulties. Scientists from the University of Edinburgh and the Royal Centre for Defence Medicine, United Kingdom, examined the effects of an extreme challenge in six women who skied over 1,000 miles in 61 days, while pulling sleds weighing about 176 pounds. All in an environment of very low temperatures and high winds. The investigators monitored several health markers before and after the expedition, including stress, reproductive and metabolic function and fat and muscle levels.

Findings indicated that muscle levels and hormone markers of stress, fertility and bone strength were preserved, despite enduring such extreme exercise and losing on average 22 pounds in body fat. Some tests even showed evidence of exercise-related benefits by two weeks after the expedition had ended. These findings contain some potentially myth-busting data on the impact of extreme physical activity on women.

These investigators have shown that, with appropriate training and preparation, many of the previously reported negative health effects of such challenges can be avoided. The low number of highly-selected women means the findings may not be applicable to all. More research is needed to compare these measures in women with men, and to explore whether factors like dietary content, adequate sleep or psychological preparation might have protected women against the negative effects of extreme exercise with weight loss.

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Is Weightlifting Good for Your Heart? If Yes, How Much Is Enough?

Aerobic exercise, such as running, reduces the risk of cardiovascular disease events like heart attack or stroke; thus, it is commonly called “cardio” exercise. Weightlifting has been traditionally considered to improve sports performance in athletes. Yet, limited evidence exists to clarify whether weightlifting reduces heart attack or stroke risk, which represents major causes of death in the general population. In this study, the researchers investigated the possible relationship between resistance exercise with the risks of developing cardiovascular disease and premature death.

Preventive health exam records of 12,591 adults (average age 47) provided the data for this study. The study found even doing weightlifting exercises one time per week (or less than one hour/week) reduced the risk for a heart attack or stroke by 40-70 percent. This was true regardless of whether or not the subjects reported participating in aerobic exercise! This study fills an important knowledge gap about the benefits of weightlifting–supporting that it may reduce risk of heart attack or stroke, beyond the well-documented benefits of aerobic exercise

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Caffeine May Increase Cardiovascular Risk During Exercise

Regular exercise is known to be good for heart health, but the risk of a heart attack temporarily increases during an exercise session. Most heart attacks and strokes are caused by a blood clot that disrupts blood flow to the brain or heart. During exercise, there is an increase in the amount of certain proteins in the blood that promote blood clot formation.

At the same time, there is typically an increase in other proteins that are responsible for dissolving a clot. It is believed that this balance between clot formation and dissolution is important for preventing a heart attack. Caffeine is widely consumed by many people and can be used to improve athletic performance. However, caffeine may affect the heart and blood vessels in ways that are not healthy for some people.

This recent study conducted by scientists at Ball State University studied 48 young healthy men, evaluating the effect of caffeine on markers of blood clotting potential–with measures taken before and after exercise. This study showed that a single dose of caffeine increased blood clotting activity during exercise more than a placebo, but caffeine did not affect the proteins that dissolve blood clots. These results suggest caffeine may cause changes in the blood that promote clot formation and, thus, increase cardiovascular risk during exercise.

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Heart Health & Brain Health Go Hand-in-Hand

According to the Center of Disease Control and Prevention, heart disease accounts for one of every four deaths in the United States. Many of the causes of heart disease are well-known, including hypertension, hyperlipidemia, diabetes and obesity. Fortunately, there are also well-known lifestyle and behavior changes that can drastically reduce the risk of heart disease and include: smoking cessation, eating a healthy diet and exercising.

Despite the multitude of data showing that lifestyle behaviors can reduce the risk of heart disease and improve cardiovascular health, the Framingham Offspring Study recently reported that the percentage of people with ideal cardiovascular health (using the American Heart Association’s definition of Ideal Cardiovascular Health) has declined over the past 20 years.

Even in the absence of heart disease, the increasing percentage of Americans with less than ideal cardiovascular health translates to greater risk of heart disease and increased all-cause mortality. Because the heart and cardiovascular system are vital factors in overall health, other organ systems will be affected by less-than-ideal cardiovascular health. Importantly, adults having an ideal cardiovascular health score during the middle-aged years had a lower risk of cognitive decline and dementia. In addition, large-scale epidemiological studies have continued to show a strong correlation between cardiovascular health and brain health.

What is the link between cardiovascular health and brain health?

It is possible that heart disease and Alzheimer’s disease or dementia have common risk factors and that is why there are correlations between these conditions. However, the brain requires a large amount of blood flow, which needs to be precisely controlled to maintain optimal neuronal function. If a patient has a problem with the function of the heart or blood vessels, this could prevent adequate blood flow supply to the brain and eventually affect brain function and cognition. We know that patients with congestive heart failure have higher incidence of dementia. In heart failure patients, a reduced capacity of the left ventricle to pump blood (i.e. ejection fraction) is associated with poor cognitive test scores.

The function of the large vessels supplying blood flow to the brain are also important to overall brain health. A paper published almost 70 years ago first reported that patients with carotid occlusion (due to atherosclerosis) eventually progressed to dementia. This early case study was the first to suggest that mild hypoperfusion of the brain, due to large vessel stenosis, could lead to dementia.

Dysfunction in the heart (or pump) or the large blood vessels (or conduits) is associated with reduced cognitive function, but the small blood vessels in the brain that control the blood supply to neurons may also contribute to the link between cardiovascular health and brain health. This hypothesis was first proposed decades ago, based on evidence of disrupted microvessel structure in the brains of Alzheimer’s disease patients. Disruption in the microvessels can lead to hypoperfusion, disrupt the blood-brain-barrier or reduce the ability of the brain to utilize glucose. Collectively, an interruption at any segment of the blood delivery system (heart, large and small blood vessels) could impair the ability of the brain to function optimally.

physical activity recommendationsNow, for the good news: Because of the link between heart health and brain health, we know that lifestyle behaviors (like exercise!) can reduce the risk of developing heart disease AND developing cognitive decline. Older adults who are more physically active have better brain health compared with sedentary counterparts, suggesting a protective effect of exercise. And although more research is necessary to determine how exercise may promote healthy brain aging and what might be the optimal training program, using what we know about what works for heart health and following ACSM’s guidelines for physical activity is a great place to start. Remember to take care of our heart so that our heart can take care of our brain.

By: Jill Barnes, Ph.D., FACSM, is an Assistant Professor at the University of Wisconsin-Madison in the Department of Kinesiology and has an affiliate faculty appointment in the Division of Geriatrics and Gerontology in the School of Medicine and Public Health.

Related Article: Heart disease and brain health: Looking at the links

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Exercise for the Prevention and Treatment of Hypertension – Implications and Application

3 Key Points:

  • Regular aerobic exercise results in reductions in blood pressure of 5-7 mmHg among individuals with hypertension and these reductions translate to a reduced risk of CVD of 20-30%.
  • Emerging research suggests that dynamic resistance exercise may also serve as an efficacious strategy to lower blood pressure to levels similar to aerobic exercise.
  • Special consideration should be given to signs/symptoms or presence of disease, concomitant drug therapy, and other comorbidities in order to optimize CVD risk reduction and improve overall health. The goal of preparticipation screening should be to risk classify individuals at risk for an adverse or life threatening response to exercise while decreasing barriers to physical activity participation.

Cardiovascular disease (CVD) is the leading cause of death in the United States (U.S.) and accounts for 1 out of every 3 deaths in U.S. adults. High blood pressure (BP) or hypertension is the most common, costly, but modifiable major risk factor for the development of CVD and premature mortality, affecting nearly half (46%) of U.S. adult population (PMID: 30700139).

Hypertension is the most common, costly, and modifiable CVD risk factor.

In 2017, The American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines released new guidelines, which now define ‘hypertension’ as:

  • having a resting systolic BP (top number) of 130 mmHg or greater
  • having a resting diastolic BP (bottom number) of 80 mmHg or greater
  • taking antihypertensive medication
  • being told by a physician or health professional on at least two occasions that one has high BP
  • or any combination of these criteria

Blood Pressure Guidelines Zaleski

The ACSM recommends that individuals with hypertension engage in moderate intensity, aerobic exercise 5-7 d/wk, supplemented by resistance exercise 2-3 d/wk and flexibility exercise ≥2-3 d/wk.

Participation in regular exercise is a key modifiable determinant of hypertension and is recognized as a cornerstone therapy for the primary prevention, treatment, and control of high BP. On average, regular aerobic exercise lowers resting systolic BP 5-7 mmHg, while resistance exercise lowers resting systolic BP 2-3 mmHg among individuals with hypertension. These BP reductions follow the “law of initial values” such that individuals with higher baseline BP values experience even greater reductions in BP from exercise training. In other words, exercise works best in those who can stand to benefit the most.

BP reductions of this magnitude lower overall CVD risk by 20-30%. For these reasons all major public health organizations universally recommend aerobic exercise for the primary prevention and treatment of hypertension. Similar to a drug prescription, individuals can be “prescribed” an exercise prescription for the prevention, treatment, and control of high BP following the FITT principle:

Frequency: How often?

Intensity: How hard?

Time: How long?

Type: What kind?

Specifically, the ACSM recommends the following exercise prescription for individuals with hypertension:

Frequency:

For aerobic exercise, 5-7 d/wk, supplemented by resistance exercise 2-3 d/wk and flexibility exercise ≥2-3 d/wk.

The frequency of aerobic exercise is slightly greater than those with normal BP (i.e., 3-5 d/wk). In fact, individuals with hypertension are encouraged to engage in greater frequencies of aerobic exercise than those with normal BP because we know that a single bout of aerobic exercise results in immediate reductions in BP of 5-7 mmHg, that persist for up to 24 hr (i.e., postexercise hypotension). For this reason, individuals with hypertension are encouraged to exercise on most days of the week in order to benefit from the acute effects of aerobic exercise on BP.

Intensity:

Moderate [i.e., 40-<60% VO2R or 11-14 on a scale of 6 (no exertion) to 20 (maximal exertion) level of physical exertion or an intensity that causes noticeable increases in heart rate and breathing] for aerobic exercise; moderate to vigorous (60-80% 1RM) for resistance; and stretch to the point of feeling tightness or slight discomfort for flexibility.

New and emerging evidence suggest that the magnitude of the BP reductions that result from aerobic exercise occur as a direct function of intensity, such that the more vigorous the intensity, the greater the resultant BP reductions (PMID: 26423529). Individuals who are willing and able may consider progressing to more vigorous intensities, however, the risk-to-benefit ratio has not yet been established.

Time:

For aerobic exercise, a minimum of 30 min or up to 60 min/d for continuous or accumulated aerobic exercise. If intermittent, begin with a minimum of 10 min bouts.

New and emerging research has shown that short bouts of exercise (3-10 min) interspersed throughout the day may elicit BP reductions similar in magnitude to one continuous bout of exercise and may be a viable antihypertensive lifestyle strategy for individuals with limited time.

Type:

For aerobic exercise, emphasis should be placed on prolonged, rhythmic activities using large muscle groups such as walking, cycling, or swimming. Resistance training may supplement aerobic training and should consist of 2-4 sets of 8-12 repetitions for each of the major muscle groups. For flexibility, hold each muscle 10-30 s for 2-4 repetitions per muscle group. Balance training (neuromotor) exercise training is also recommended in individuals at high risk for fall (i.e., older adults) and is likely to benefit younger adults as well.

Blood pressure reductions appear to occur in a dose-response manner such that greater volumes of exercise elicit greater reductions in blood pressure. Progression to the Ex Rx should be gradual, avoiding large increases in any of the FITT components of the Ex Rx, especially intensity for most individuals with hypertension.

A recent meta-analysis demonstrated dynamic resistance exercise training to result in BP reductions similar in magnitude to aerobic exercise training (PMID: 27680663). These results suggest that the antihypertensive benefits of resistance exercise training may have been largely underestimated and warrant reappraisal in the near future. Note that, inhaling and breath-holding while engaging in the actual lifting of a weight (i.e., Valsalva maneuver) can result in extremely high BP responses, dizziness, and even fainting and should be avoided during resistance training.

Practical Applications

Accurate BP assessment is critical for a) the initial diagnosis of hypertension and b) to establish a baseline BP to properly evaluate the influence of lifestyle intervention strategies across time. Proper patient positioning and preparation are critical for ensuring accuracy of BP values. Caffeine, exercise, and smoking should be avoided at least 24 hr before BP assessment. Prior to the first reading, the patient should be:

  • seated quietly and not talking for at least 5 min prior to or during the measurements
  • legs uncrossed and flat on the floor
  • bladder empty
  • back supported upright
  • arm supported at heart level
  • with an appropriate sized cuff

American Heart Association standards state that BP should be measured three times in each arm, separated by at least 1 min, and averaged. This is particularly important given that the first reading is often the highest reading. Preferably, the same exercise professional should measure BP on the same patient and using the same BP monitoring device. Approximately ~25% of patients experience “white-coat hypertension” such that BP readings obtained in the presence of a healthcare provider appear elevated, however, home or ambulatory BP values are within normal ranges. Patients with suspected white-coat hypertension may be referred to their healthcare provider for proper evaluation.

Appropriate preparticipation health screening should be implemented to identify at-risk individuals who may require medical clearance before they begin an exercise program (PMID: 2647375). Although exercise is safe for most individuals, there is a small risk of cardiovascular complications in certain susceptible individuals, particularly among sedentary adults with known or underlying CVD who perform vigorous-intensity exercise they do not usually engage in. The ACSM preparticipation guidelines emphasize the public health message that exercise is important for all individuals and largely triages individuals on the basis of current physical activity levels, desired exercise intensity, and the presence of known or underlying CVD, metabolic, and/or renal disease.

As such, individuals with hypertension cleared to exercise (by the preparticipation algorithm or healthcare provider) should be encouraged to progress gradually, avoiding large increases in any of the components of the FITT. Progression should begin by increasing exercise duration over the first 4-6 wk, followed by an increase in frequency and intensity to achieve the recommended volume of 150 min/wk or 700-2000 kcal/wk over the next 4-8 mo. Progression may be individualized based on tolerance and preference in a conservative manner.

Lifestyle modifications, such as regular aerobic exercise, are fundamental for the prevention, treatment, and control of hypertension. When lifestyle interventions are not effective in achieving treatment BP goals, antihypertensive therapy may be required to optimize CVD risk reduction. Whenever possible, an interdisciplinary, collaborative approach involving the patient, healthcare provider(s), and exercise professional will largely improve lifestyle and pharmaceutical adherence, translating to greater BP control and overall health, which is the ultimate goal in the treatment of hypertension.


Author: Amanda Zaleski, PhD is an American Heart Association Postdoctoral Fellow in Amanda Zaleski PhDthe Department of Kinesiology at the University of Connecticut. She is also a Project Manager and Evidence-Based Credentialed Analyst for the forthcoming ACSM Hypertension Position Stand Update and Co-Chair of the Communications Committee for New England ACSM.


Recommended Reading: New Blood Pressure Guidelines, Preparticipation Screening

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