Physical Exercise and Aging
5.2 Physical Exercise Is Multifaceted
© Springer International Publishing AG 2018 35
S. Masiero, U. Carraro (eds.), Rehabilitation Medicine for Elderly Patients, Practical Issues in Geriatrics, DOI 10.1007/978-3-319-57406-6_5
A. Paoli, MD, PhD
Nutrition and Exercise Physiology Laboratory, Department of Biomedical Sciences, University of Padua, Padua, Italy
e-mail: [email protected]
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mandatory to create tailored programs for healthy and unhealthy subjects and espe- cially for elderly.
Classical endurance training protocols usually induce an increase in VO2max (maximal oxygen consumption) that is related to a complex cascade of effects that results in modifications in both cardiovascular system and trained skeletal muscles.
In skeletal muscle, ET stimulates a shift from IIX heavy chain myosin phenotype to IIa and I types. Compared to IIx-type fibers, I-type fiber showed an increase of oxi- dative characteristics, such as muscle capillarity, muscle mitochondrial volume, and mitochondrial density, and oxidative enzymes: enzymes of the Krebs cycle and oxi- dative phosphorylation such as SDH (succinate dehydrogenase), CS (citrate syn- thase), and Cytox (cytochrome c oxidase) (see Table 5.1).
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 stimulat- ing 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 economi- cal 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 myo- sin heavy chain (MHC) to another; these changes are related to the characteristics of training [6–8]. 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
Table 5.1 Effects of aerobic and resistance exercise on different variables 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 ↑ ↑↑
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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
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)
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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.