Versatility of Protocols for Resistance Training and Assessment Using Static and Dynamic Ladders in Animal Models

Summary

The present protocol describes resistance training and testing using static and dynamic ladders in animal models.

Abstract

Resistance training is a physical exercise model with profound benefits for health throughout life. The use of resistance exercise animal models is a way to gain insight into the underlying molecular mechanisms that orchestrate these adaptations. The aim of this article is to describe exercise models and training protocols designed for strength training and evaluation of resistance in animal models and provide examples. In this article, strength training and resistance evaluation are based on ladder climbing activity, using static and dynamic ladders. These devices allow a variety of training models as well as provide precise control of the main variables which determine resistance exercise: volume, load, velocity, and frequency. Furthermore, unlike resistance exercise in humans, this is a forced exercise. Thus, aversive stimuli must be avoided in this intervention to preserve animal welfare. Prior to implementation, a detailed design is necessary, along with an acclimatization and learning period. Acclimatization to training devices, such as ladders, weights, and clinical tape, as well as to the manipulations required, is necessary to avoid exercise rejection and to minimize stress. At the same time, the animals are taught to climb up the ladder, not down, to the resting area on the top of the ladder. Resistance evaluation can characterize physical strength and permit adjusting and quantifying the training load and the response to training. Furthermore, different types of strength can be evaluated. Regarding training programs, with appropriate design and device use, they can be sufficiently versatile to modulate different types of strength. Furthermore, they should be flexible enough to be modified depending on the adaptive and behavioral response of the animals or the presence of injuries. In conclusion, resistance training and assessment using ladders and weights are versatile methods in animal research.

Introduction

Physical exercise is a determinant lifestyle factor for promoting health and decreasing the incidence of the most prevalent chronic diseases as well as some types of cancer in humans¹.

Resistance exercise has raised interest because of its overwhelming relevance for health throughout life², especially due to its benefits in counteracting age-related diseases that affect the locomotor system, such as sarcopenia, osteoporosis, etc³. Moreover, resistance exercise also affects tissues and organs not directly involved in the execution of movement, such as the brain⁴. This relevance in recent years has encouraged the development of resistance exercise models in animals to study the underlying tissular and molecular mechanisms, when it is not possible in humans or when the animals provide better insight and are a more controlled model.

Unlike resistance exercise in humans, for animal models researchers usually rely on forced procedures. However, aversive stimuli must be avoided in this context, mainly to preserve animal welfare, reduce stress, and decrease the severity of the experimental procedures⁵. It should be noted that animals enjoy exercise even in the wild⁶. For these reasons, it is necessary to improve adaptation to the experiment through prolonged stepwise acclimatization.

The devices, materials, and protocols used for resistance training and assessment in experimental animals must allow the precise control and modulation of numerous variables: load, volume, speed, and frequency⁷. They should also allow different types of muscle contractions to be performed: concentric, eccentric, or isometric. Considering the above, the protocols used should be able to specifically evaluate or train for different applications of strength: maximal strength, hypertrophy, speed, and endurance.

There are several methods of strength training, such as jumping in water^8,9, weighted swimming in water¹⁰, or muscle electrostimulation¹¹. However, static and dynamic ladders are versatile devices that are widely used^12,13,14.

Resistance assessment in experimental animal models provides valuable information for many research settings, such as describing the phenotypic characteristics of genetically modified animals, evaluating the effect of different intervention protocols (dietary components supplementation, drug treatments, microbiota transplantation, etc.), or assessing the effect of training protocols. Training models provide insight into the physiology of adaptation to strength exercise, which helps to better understand the effect of exercise on health status and pathophysiology.

Consequently, there is no universal protocol for resistance training or the functional assessment of strength in animal models, so versatile protocols are needed.

The aim of this study is to identify the most relevant factors to be considered when designing and applying a protocol for resistance training and evaluation using static and dynamic ladders in animal models, as well as provide specific examples.

Protocol

The methods presented in this protocol have been evaluated and approved by the animal research technical committee (reference PROAE 04/2018, Principado de Asturias, Spain). 1. Planning Carefully select animals for the study based on the characteristics of interest (genetically modified, pathology models, age, etc.) and apply specific adaptations to the protocol (climbing without weights, reducing the number of rungs to climb, and inclination). Identify th…

Representative Results

Results with static ladder The progressive resistance training protocol used and described by Codina-Martinez et al.4 (Table 4) was tested in a preliminary study consisting of 7 weeks of training on a static ladder with 6-months-old wild-type C57BL6J mice (n = 4). In this preliminary study, incremental tests to assess maximal strength were performed before and after the training period. We observed a 46.4% increase in maximal strength, meaning that at the en…

Discussion

Training is an intervention with multiple applications in research, apart from the study of exercise itself. Thus, the analysis of its effect on ageing²⁰ or certain pathological conditions and physical therapy²¹ has received much attention in recent years. In addition, numerous authors have analyzed the effect of pharmacological²² or dietary²¹ interventions on physical fitness. In this context, interest has…

Materials

Dynamic ladder	in-house production
Elastic adhesive bandage 6 cm x 2.5 m	BSN medical	4005556
Gator Clip Steel NON-INSUL 10A	Digikey electronics	BC60ANP
Static ladder	in-house production
Weights	in-house production
Wire for holding weigths	in-house production