Thursday, March 14, 2013

Research Shorts (NCSF).

Just Stand up to Increase Daily Muscle Activity
Recent findings suggest that both the lack of physical activity and prolonged periods of sedentary behavior significantly increase the risk of chronic diseases. A growing concern is that they function independently of each other. Therefore, individuals meeting minimum guidelines for movement but working in environments where movement is limited throughout the day are also at risk. There seems to be a relevant relationship between the time spent seated and the risk for morbidity. Interestingly, even exercising three times a week at a moderate intensity, utilizing fitness equipment appears to be inadequate to offset an otherwise sedentary lifestyle. One investigation sought to examine the response of select musculature to long periods of sedentarism. The authors analyzed quadriceps and hamstring muscle inactivity as well as activity during normal daily life. Eighty-four volunteers (44 females, 40 males, 44.1 ±17.3 years, 172.3 ±6.1 cm, 70.1 ±10.2 kg) were measured during normal daily activities using shorts that measured muscle electromyographic (EMG) activity (recording time 11.3 ±2.0 hours). EMG data was normalized to isometric MVC (EMG(MVC)) during knee flexion and extension, and inactivity threshold of each muscle group was defined as 90% of EMG activity during standing (2.5 ±1.7% of EMG(MVC)). During normal daily life, the average EMG amplitude was 4.0 ±2.6% and average activity burst amplitude was 5.8 ±3.4% of EMG(MVC); this average being below the EMG level required for walking (5 km/h corresponding to EMG level of about 10% of EMG(MVC)). Using the proposed individual inactivity threshold, thigh muscles were inactive 67.5 ±11.9% of the total recording time and the longest inactivity periods lasted for 13.9 ±7.3 min (2.5-38.3 min). Women had more activity bursts and spent more time at intensities above 40% EMG(MVC) than men.
In conclusion, during normal daily life, the locomotor muscles are inactive about 7.5 hours, and only a small fraction of the musculature’s maximal voluntary activation capacity is used. Some daily non-exercise activities such as stair climbing produce much higher muscle activity levels than brisk walking, and replacing sitting with standing can considerably increase cumulative daily muscle activity. Trainers need to influence clients to not only train 2-3 times per week, but additionally participate in regular daily movement. Taking the stairs, walking the dog, and simply moving more will certainly contribute to reduce health risk associated with sedentarism.
Reference: PLoS One, 2013

Nutritional Considerations for Minimizing Sarcopenia among Older Adults
The United States has an aging population, and with that comes an increasing propensity toward health concerns. It is well documented that older age is associated with high risk for cardio-metabolic disease as well as a decline in movement capabilities. Clearly, engaging in appropriate exercise is critical to the maintenance of independence as well as a greater quality of life among older adults. Research demonstrates a lack of physical activity during the later decades of life strongly contributes to the estimated 10-30% loss of biological function experienced over this period. It should be understood that this functional decline can also be related to the presence of disease, specific genetic and environmental factors, poor mental health, and pre-existing injuries such as low back pain. Sarcopenia is defined as an age-related loss of muscle mass with associated reductions in strength and power. The loss of protein from the heavy myosin chains of muscle fibers, alongside neural and connective tissue decline collectively serve as the primary culprits behind musculoskeletal system deterioration among individuals over 60 years of age. The mechanisms behind this process of muscle wasting (which can further promote inactivity) include hormonal changes, a loss of fast-twitch fibers, glycation of bodily proteins (impairs function of cells), and insulin resistance.
Nutrition also has a significant part to play in age-related functional decline. A recent study published in Osteoporosis International sought to identify a number of related factors, and how they may contribute to sarcopenia. The role of dietary protein, acid-base balance, vitamin D, calcium, and other select nutrients such as the B-complex vitamins were evaluated via an extensive literature review.
The following recommendations/considerations were made based on a review of current research:
  • A minimal protein intake equaling 1.0-1.2 g/kg of body weight per day may be optimal for older adults to maximize muscle function, regeneration and recovery
  • A moderate inverse relationship between vitamin D status and muscle strength was found, indicating a need for adequate intake to maintain optimal bone and muscle function
  • Chronic ingestion of acid-producing diets appear to have a negative impact on muscle performance, indicating acid-base balance may be integral to minimizing muscle wasting
    • Artificial sweeteners, excess animal protein intake, alcohol, select fruits and vegetables, most processed grains, and select condiments and spices are known to be acid-promoting
    • Signs of high systemic acidity: fatigue, breathlessness, frequent muscle pain/cramping
  • Decreases in vitamin B12 and folic acid intake may also impair muscle function through their action on homocysteine (has an impact on collagen in bone and other connective tissues)
It is clear that regular weightlifting, power training, ROM activities, and specialized nutritional strategies should be used when training older adults to minimize muscle loss and the consequent decrease in overall function. Resistance training should emphasize re-establishing a functional skeletal position and focus on muscle balance. One area of emphasis is strengthening the posterior chain, particularly the muscles that act on the humerus and scapula while lengthening the anterior chain as hip flexors and abdominals become tight due to gravitationally influenced migration into flexion. Power training should aim to recruit fast-twitch fibers but be modified to ensure safe movements during higher-velocity movement. Emphasis should be placed on the concentric aspect of the movement which can include rapid chair stands, concentric-only MB throws, and bodyweight movement drills for those at higher risk. Be cautious with individuals suspected of osteoporosis as the vertebrae, hip and wrist are sensitive to injury.
It can be hoped that future research will provide greater data related to specific quantities of key nutrients essential to limiting sarcopenia, so that these intake guidelines may be combined with an appropriate resistance training program to an effect of enhanced quality of life among the elderly.
Reference: Osteoporosis International, December 2012

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