Physical Exercise and Aging

 

Aerobic/endurance

Resistance/strength

Skeletal muscle morphological and physiological adaptations

Muscle hypertrophy


↑↑↑

Muscle CSA

≅↑

↑↑↑

Myofibrillar protein synthesis

≅↑

↑↑↑

Mitochondrial protein synthesis

↑↑


Capillarization

↑↑


Mitochondrial number, size, and function

↑↑↑

≅↑

Exercise performance

Muscle strength (power)



Lactate buffer capacity

↑↑

↑↑

VO2max

↑↑↑

≅↑

Neural adaptation


↑↑↑

Endurance capacity

↑↑↑


Anaerobic capacity


↑↑



Regarding morphological changes muscle fiber cross-sectional area is generally poor or not affected by endurance-type exercise except when exercised muscles were immobilized. Endurance training also leads to a shift in metabolism stimulating to a higher lipid utilization as fuel and to an increase in IMCL (intramyocellular lipid) and glycogen stores.

Instead classic strength training protocols influence mainly muscle and muscle fiber cross-sectional area. It is important to underline that the earliest adaptation during a ST protocol belongs to a modification of neuromuscular function [5]; this mechanism allows strength increase with little or null structural adjustments, thus a more economical adaptation. After few weeks ST stimulates the increase of muscle cross-sectional area due mainly to an increase in the number of myofibrils, notably of the fast fiber types (type IIA and type IIX) [6]. Training affects also the shifts from one type of myosin heavy chain (MHC) to another; these changes are related to the characteristics of training [68]. Even though mitochondria and capillaries are little affected by ST and mitochondrial volumes and capillary densities are low in strength-trained athletes, the role of mitochondria in muscle mass maintaining has been recently highlighted [9].

With the onset of the sixth decade in life, there is a gradual increases of many degenerative processes (described elsewhere in this book); these processes cause a decrease of muscle power (dynapenia) [10] and muscle mass (sarcopenia) [11, 12]. These modifications are related both to neural (e.g., loss of alpha motoneurons) and morphological changes (e.g., reduced number and size of muscle fibers) [10].

General muscular weakness is highly associated with impaired mobility and an increased risk for falls in the elderly; for this reason RT is a key point for improving elderly’s quality of life [13]. As a matter of fact, lower limb muscle weakness was identified as the main intrinsic fall-risk factor in the elderly [14]. It is interesting to observe that although the age-related decline in muscle strength is associated with skeletal muscle mass loss, other studies reported a greater decline in muscle strength compared to muscle size [15].

Even though exercise cannot completely prevent aging-related loss of strength, due mainly to the modification of the neuromuscular system, RT showed great age-related changes. Many studies in the last years, starting from the seminal paper of Frontera et al. [16], showed the importance of RT on muscle mass maintenance over years. While the calculated loss of strength is 1.3% by year after 52 years of age [17], other researches showed that from 60 years old to 72 years old, there is a decline of isokinetic knee extensor torque of −24% and in quadriceps cross-sectional area (CSA) of −16%. On the contrary only 12 weeks of high intensity RT (80% of 1 RM) leads to a 16% increase in isokinetic torque and 11% in knee extensor CSA [18].

Unfortunately PE is often prescribed by physicians in a very “low-intensity,” “low-volume” manner [10]. It is of paramount importance when developing RT programs, considering all the various training variables such as frequency, duration, exercises, sets, recovery, intensity, repetitions, and type of contractions (see Table 5.2). Adverse events in healthy elderly are very rare. Most adverse events are usually related to musculoskeletal problems, but serious adverse events were very rare and appear not to be directly related to the exercise program. Anyway subjects at risk of RT’s induced adverse events should undergo to a complete specialized health screening. These subjects are those with high-grade hypertension, diabetic neuropathy, and/or retinopathy, with ischemic and cerebrovascular heart diseases and heart failure.


Table 5.2
Different training variables in endurance exercise and resistance training




















































Endurance training

Resistance training

Variable

Examples

Variable

Examples

Duration (total duration of training)

Minutes, hours

Muscle contraction type

Eccentric, concentric, isometric

Intensity (relative effort)

% Maximal heart rate (HRmax)

% Heart rate reserve (HRres)

% Maximal oxygen consumption (VO2max)

Type of load

Barbell, dumbbell, elastics, calisthenics, weight machines

Type of exercise (exercise modalities)

Running, cycling, rowing

Volume

Sets × repetitions
   
Training structure

Total body, split routine, numbers of muscle area
   
Rest between sets

Seconds, minutes
   
Speed of movement

Slow, explosive
   
Training frequency (amount of times per week)
 



5.3 PE Frequency


At least 2 (from 2 to 4) days per week were recommended. Two/three times of endurance training and two sessions of RT. The most common approach is 2 times a week of ET and 1–2 times a week of RT; in our opinion 2 times a week for ET and 2 times for RT should be an adequate frequency. Another solution could be 3 times a week on alternating days (e.g., Monday, Wednesday, and Friday) of RT + ET, the so-called circuit training [3, 4, 19, 20]; all the above methodologies are performed as a “total body” routine. An alternative approach exercise session with the “total body” is the so-called “split routine” where routine is performed 2–3 times per week. In this methodology subjects are exercising selected muscle groups on 1 or 2 days per week, while the remaining are exercised on a separate 1 or 2 days per week (e.g., chest, arms, and limbs on Monday; back, shoulder, and hamstring on Wednesday; ET on Tuesday and Thursday). When performing only RT, the typically split routine could be A, B, and C, where A is training the chest and biceps, B the lower limbs and shoulder, C the back and triceps.

Mar 29, 2020 | Posted by in GERIATRICS | Comments Off on Physical Exercise and Aging
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