Effects of exercise on neuromuscular junction components across age: systematic review of animal experimental studies

Abstract

Background: During almost one-third of our life, maturation of the nervous system promotes strength and muscle mass increase. However, as age advances, the nervous system begins to suffer a slow and continue reduction of its functions. Neuromuscular junction (NMJ) is one of the structures of which change due to aging process. Physical training leads to significant adjustments in NMJs of young and aged animals. Nevertheless, studies that aimed to investigate this effect have, in many cases, methodological variables that may have some influence on the result. Thus, this study aimed to carry out a systematic review about the effects of exercise training on the NMJ compartments of young, adult and aged animals.

Results: We searched PubMed, Google Scholar, Science Direct, Scielo and Lilacs databases for animal experimental studies that studied exercise effects on the NMJs components across age. After inclusion and exclusion criteria, we included nine articles in systematic review and two for meta-analysis (young/adult NMJ).

Conclusions: We identified that exercise training cause NMJ hypertrophy on young animals and NMJ compression on aged ones. However, many methodological issues such as age, skeletal muscle and fibers type, and type of exercise and training protocol might influence the results. Graphical abstract: Flow gram is actually to be show at results section as Fig 1.

Graphical abstract:

Flow gram is actually to be show at results section as Fig 1

Fig. 1

Forest plot presented information about endurance training effects on nerve terminal branch number of young and adult slow-twitch NMJ

Fig. 2

Forest plot presented information about endurance training effects on nerve terminal total branch length of young and adult slow-twitch NMJ

Fig. 3

Forest plot presented information about exercise effects on average branch length of the nerve terminals of young and adult slow-twitch NMJ

Fig. 4

Forest plot presented information about exercise effects on branching complexity of the nerve terminals of young and adult slow-twitch NMJ

Fig. 5

Forest plot presented information about exercise effects on end plate total perimeter of young and adult slow-twitch NMJ

Fig. 6

Forest plot presented information about exercise effects on end plate stained perimeter of young and adult slow-twitch NMJ

Fig. 7

Forest plot presented information about exercise effects on end plate total area of young and adult slow-twitch NMJ

Fig. 8

Forest plot presented information about exercise effects on total end plate stained area of young and adult slow-twitch NMJ

Fig. 9

Forest plot presented information about exercise effects on end plate dispersion of young and adult slow-twitch NMJ

Fig. 10

Forest plot presented information about exercise effects on end plate pre- to post-synaptic coupling of young and adult slow-twitch NMJ

Fig. 11

Forest plot presented information about exercise effects on fast-twitch nerve terminal branch number

Fig. 12

Forest plot presented information about exercise effects on fast-twitch terminal nerve total branch length

Fig. 13

Forest plot presented information about exercise effects on fast-twitch terminal nerve average branch length

Fig. 14

Forest plot presented information about exercise effects on fast-twitch nerve terminal branching complexity

Fig. 15

Forest plot presented information about exercise effects on fast-twitch end plate total perimeter

Fig. 16

Forest plot presented information about exercise effects on fast-twitch end plate stained perimeter

Fig. 17

Forest plot presented information about exercise effects on fast-twitch end plate total area

Fig. 18

Forest plot presented information about exercise effects on fast-twitch end plate stained area

Fig. 19

Forest plot presented information about exercise effects on fast twitch end plate dispersion

Fig. 20

Forest plot presented information about exercise effect on fast twitch end plate pre- to post-synaptic coupling