Recipient Organization
SOUTH DAKOTA STATE UNIVERSITY
PO BOX 2275A
BROOKINGS,SD 57007
Performing Department
College of Education & Human Sciences
Non Technical Summary
Maintaining independence late in life is a goal of nearly all Americans; however, chronic disease is on the rise and as a result, individuals are losing their independence prematurely. One method for improving the longevity of an individual's independence is through the maintenance of muscular strength and through the avoidance of fractures. While muscle strength and bone mass both decrease slightly with aging, our study aims to determine if diet and physical activity interventions are effective in achieving the goal of slowing muscle and bone loss. It appears clear that an appropriate resistance training regimen will help to build muscle, but it is not obvious what mode and applications of resistance training are most palatable to different groups of people. In addition to muscle and bone loss, cartilage loss leading to osteoarthritis is the fourth leading cause of disability in the United States. Even though muscle, bone, and cartilage are all separate tissues, they are all closely related and important factors in improving longevity.The focus of this proposal is to examine the following topics: (1) examine how muscle loss is affected by an individual's diet and physical activity, (2) improve the understanding of the role of diet and physical activity in the prevention of bone and cartilage loss. Several methods including surveys, observational studies, and secondary data analysis will be used to discover the role of diet and physical activity in these areas. Findings from these studies will have a broad impact across the region by informing the healthcare community regarding the appropriate dietary and physical activity interventions to prescribe for patients depending on what their goals may be. Additionally, this study may help to improve the treatment of orthopedic injuries since the findings related to slowing muscle loss could be directly related to the slowing of muscle loss in the post-injury period. Together, the information gathered from the studies in this proposal will have a large benefit to our communities through increased longevity, increased productivity, and potentially a decreased economic burden due to musculoskeletal injuries and conditions.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
The overall goal of this research is to determine the role that diet, and physical activity have in the health of muscle, bone, and cartilage throughout the lifespan. In the long-term, Improving the breadth of scientific discovery in this area will be critical to decreasing the prevalence of many conditions such as sarcopenia, osteoarthritis, and osteoporosis.1.This goal will have two secondary aims with the first being a multifactorial approach to determining factors associated with age-related muscle loss. In year 1, the trends of physical activity and diet change with aging will be examined along with the role of change in diet and physical activity in the loss of muscle with again. This objective will be critical to reversing the trend of significant muscle loss generally observed in the second half of the lifespan1,2. By attenuating muscle loss in aging individuals, we may be able to improve quality of life as well as the length of time in which older adults can remain independent. The second part of this objective will be to focus on how muscle loss can be attenuated following orthopedic injuries and surgery. Following orthopedic surgery and/or injury, a significant loss of muscle mass and function is generally observed3,4. Muscle mass loss has been well documented in studies utilizing unilateral-lower leg suspension that is designed to simulate the post-injury period3-5. Additionally, similar studies found decreases in muscle function in as little as 2 weeks5-7. While this loss of muscle mass appears to be the norm, it causes significant problems in both the athletic and general population. Athletes struggle to regain their performance because of the decrease in muscle mass and also have a greater potential for reinjury while they are in a depleted state. In the general population, and particularly among the elderly, this loss in muscle mass can be even more devastating because as people age, it is more difficult to regain muscle after it is lost. In elderly individuals, this loss in muscle mass can lead to significant disability, diminished quality of life along with an increased risk of falls. In addition to the muscle mass lost during the post-operative period, the strength of the muscle also decreases. This has obvious performance implications in athletes, as well as having the potential to extend recovery time. In the elderly, decreased strength may result in reduced independence and inability to perform activities of daily living. Many previous bed rest studies have reported that significant bone loss also occurs during times of decreased mechanical loading. The post-operative period generally results in decreased mechanical loading; however, some muscle loading will still occur during the rehabilitation process.2.We will examine how nutrition, physical activity, and muscle function affect bone health throughout the lifespan. One goal of this aim will be to examine bone loss with aging and to investigate the role of modifiable factors such as nutrition, physical activity, and muscle function in attenuating the loss of bone. Given the average cost of greater than $12,000 per fracture for hospital-related expenses as well as the added cost of skilled care facility stays and the resulting loss of independence, efforts aimed at examining factors associated with decreased age-related bone loss are necessary8. Long-term exercise has been indicated as a key predictor of decreased fall risk and fracture risk previously9; however, it is less clear if the decrease in fractures is truly due to improved bone health or improved muscle function. Considering the strong relationship between skeletal muscle and bone, it is likely a combination of the two. Fractures are not the only area of concern as it relates to bone and joint outcomes. Developing strategies for early detection and prevention of osteoarthritis (OA) is of paramount importance to public health as the disease currently affects 12% of people between 25 and 74 years old in the United States 10. One study reported a lifetime risk of almost 45% for the development of knee osteoarthritis11. Additionally, OA is one of the leading causes of physical disability throughout the world12,13 carrying an annual cost of over $42 billion associated with hip and knee replacements14. Our study will investigate potential causes of osteoarthritis such as familial associations, traumatic joint injuries, and hormonal interactions along with the interaction of these factors with physical activity and diet. Through this portion of the study, we hope to gain the knowledge and understanding necessary to develop prevention programs in the future.
Project Methods
Musculoskeletal health is a critical component to increasing longevity, improving work-related productivity, preventing falls, and improving athletic performance. However, the multifaceted nature of musculoskeletal health makes creating interventions to improve it very difficult. In order to solve this difficult problem, we must develop studies which allow researchers to identify the most important factors to improvements in musculoskeletal health. Additionally, studies must be designed to address each of the three major tissues related to musculoskeletal health (muscle, bone, and cartilage). While all three are related, the factors that influence their development may be very different and in some cases such as muscle and bone, the health of one may influence the other.Objective 1: This goal will have two secondary aims with the first being a multifactorial approach to determining factors associated with age-related muscle loss. The majority of the work in this objective will involve observational studies to establish the relationships between physical activity, nutrition, and muscle loss. To accomplish this, we must have a sample that includes individuals across the entire lifespan. The primary modes of data collection will include health history questionnaires, food frequency questionnaires, 24-hour diet records, accelerometers, and physical activity questionnaires along with anthropometric measurements such as height and weight. In addition to these survey instruments dual-energy x-ray absorptiometry (DXA) will be used to measure lean and fat mass and peripheral quantitative computed tomography (pQCT) will be used to measure muscle cross sectional area of the legs. Muscle function will be tested using a combination of field tests along with isokinetic testing and mechanography. Isokinetic testing will allow the investigators to measure peak torque production at several sites throughout the body. Mechanography is valuable in determining how individuals are able to translate their muscular strength to a task such as rising from a chair or jumping through the use of a portable force platform. The primary outcome variables in this objective will include total body lean and fat mass, muscle cross-sectional area and muscle density of the legs, isokinetic peak torque, and peak ground reaction force. To analyze cross-sectional outcomes, data from questionnaires will be used to fit multivariate regression models aimed at determining the most important variables in predicting muscle mass. When looking at longitudinal outcomes, linear mixed models will be used to determine factors that are indicative of muscle gain or loss over time. All analyses will be performed in STATA version 15.Objective 2: We will examine how nutrition, physical activity, and muscle function affect bone health throughout the lifespan. Similar to objective 1, the majority of the work in this objective will involve observational studies. However, in objective 2, the goal will be to establish the relationships between physical activity, diet, and bone health. Data collection will consist of health history questionnaires including medications that are known to affect bone as well as fracture and arthritis history. In addition, food frequency and 24-hour diet records will be used to measure dietary intakes and physical activity questionnaires will be used to estimate moderate and vigorous physical activity. Bone and joint health are highly body-size dependent and therefore height and weight will be measured and will serve as key covariates in the analysis of this data. Outcomes of interest in this objective will be history of fractures, history of osteoarthritis as well as bone measurements obtained via DXA and pQCT. DXA data will allow us to look at bone mass at the hip and spine as well as allowing us to have a reliable measure of lean mass and fat mass to use as a covariate. Bone cross-sectional area and volumetric bone mineral density (vBMD) at the tibia and forearm will be measured using pQCT. To investigate changes that may lead to osteoarthritis, subchondral trabecular bone mineral density will be measured in the knee using pQCT. Cross-sectional continuous data will be analyzed using multivariate linear regression and logistic regression will be used when the outcome variables are binary such as fracture occurrence or osteoarthritis diagnosis. Longitudinal outcomes will follow a similar methodology; however, linear mixed models will be used to account for the correlation of measurement within individuals over time. All data analyses for objective 2 will be performed using STATA 15.