Muscle hypertrophy and ladder‐based resistance training for rodents: A systematic review and meta‐analysis

Abstract

This study aimed to review the effects of ladder‐based resistance training (LRT) on muscle hypertrophy and strength in rodents through a systematic review with meta‐analysis. We systematically searched PubMed/Medline, SportDiscuss, Scopus, Google Scholar, Science Direct, and Scielo database on May 18, 2020. Thirty‐four studies were included measuring total (mCSA) or mean muscle fibers cross‐sectional area (fCSA) or maximum load‐carrying capacity (MLCC) or muscle mass (MM). About the main results, LRT provides sufficient mechanical stimulation to increase mCSA and fCSA. Meta‐analysis showed a significant overall effect on the fCSA (SMD 1.89, 95% CI [1.18, 2.61], p < .00001, I2 = 85%); however, subgroup analysis showed that some muscle types might not be hypertrophied through the LRT. Meta‐analysis showed a significant training effect on the MM (SMD 0.92, 95% CI [0.52, 1.32], p < .00001, I2 = 72%). Sub‐group analysis revealed that soleus (SMD 1.32, 95% CI [0.11, 2.54], p = .03, I2 = 86%) and FHL (SMD 1.92, 95% CI [1.00, 2.85], p < .0001, I2 = 71%) presented significant training effects, despite moderate heterogeneity levels (I2 = 72%). MLCC increases considerably after a period of LRT, regardless of its duration and the characteristics of the protocols (SMD 12.37, 95% CI [9.36, 15.37], p < .00001, I2 = 90%). Through these results, we reach the following conclusions: (a) LRT is efficient to induce muscle hypertrophy, although this effect varies between different types of skeletal muscles, and; (b) the ability of rodents to carry load increases regardless of the type and duration of the protocol used.

Postsynaptic cleft density changes with combined exercise protocols in an experimental model of muscular hypertrophy

“…25,26 Type II and IIx fibers increased in the LC group due to the additional load used to carry out the vertical ladder protocols and the standards established during the protocol sessions, which refer to an experimental model of muscle hypertrophy. 22,23 While with the vertical ladder-based training in the LC group, we observed greater type II and IIx fibers, indicating hypertrophy of these muscle fibers due to their characteristic of greater strength production, contraction speed, calcium influx, and adaptive sensitivity. 27,28 In the CC group, the increase in the IIx fibers' CSA demonstrated the adaptation to the glycolytic/oxidative characteristics predominant physiologically and necessary to perform the exercise with and without a load in different sessions.…”

“…19 The smaller dispersion in the CC group was directly associated with reducing CSA type I muscle fibers and the predominance with this fiber type in the biceps brachii muscle. 22,35 Also, the measurements of the postsynaptic cleft in C group showed morphometric characteristics data with minimal reduction with an increase in density in response to different physical exercises; regarding the LC group, there was mainly a reduction in their structure and density, different from the CC group, which presented an increase in these aspects due to specific exercises. 36,37 The changes indicated that the association of the protocols promotes adaptations in adult rats related to the NMJ density, decreasing with the arrival of adulthood, and the CC protocol maintained their distribution as the main adaptation.…”

“… 20 In addition, it can be applied to elderly animals, 21 but it is mainly used for adult animals, and has shown positive results such as tissue maintenance, hypertrophy, and increased strength. 22 …”

“…20 In addition, it can be applied to elderly animals, 21 but it is mainly used for adult animals, and has shown positive results such as tissue maintenance, hypertrophy, and increased strength. 22 The biceps brachii muscle is constantly used in daily activities and works in different physical exercise protocols with and without load. The combined vertical ladder-based protocols can demonstrate new benefits to the biceps brachii tissue morphology and in their postsynaptic elements.…”

Ladder-based resistance training with the progression of training load altered the tibial nerve ultrastructure and muscle fiber area without altering the morphology of the postsynaptic compartment

“…At an experimental level, ladder-based resistance training (LRT) induces muscle hypertrophy like human RT ( Lourenço et al, 2020 ). According to Krause Neto et al (2022a) , the progression of the external training load, either by total or relative training mass, is also critical for rodent muscular hypertrophy.…”