Weight Pulling: A Novel Mouse Model of Human Progressive Resistance Exercise

Abstract

This study describes a mouse model of progressive resistance exercise that utilizes a full-body/multi-joint exercise (weight pulling) along with a training protocol that mimics a traditional human paradigm (three training sessions per week, ~8–12 repetitions per set, 2 min of rest between sets, around two maximal-intensity sets per session, last set taken to failure, and a progressive increase in loading that is based on the individual’s performance). We demonstrate that weight pulling can induce an increase in the mass of numerous muscles throughout the body. The relative increase in muscle mass is similar to what has been observed in human studies, and is associated with the same type of long-term adaptations that occur in humans (e.g., fiber hypertrophy, myonuclear accretion, and, in some instances, a fast-to-slow transition in Type II fiber composition). Moreover, we demonstrate that weight pulling can induce the same type of acute responses that are thought to drive these long-term adaptations (e.g., the activation of signaling through mTORC1 and the induction of protein synthesis at 1 h post-exercise). Collectively, the results of this study indicate that weight pulling can serve as a highly translatable mouse model of progressive resistance exercise.

Muscle Hypertrophy in a Newly Developed Resistance Exercise Model for Rats

“…Perhaps this mechanical maneuver recruits the plantaris more than the gastrocnemius or the soleus muscles. The mechanical maneuver of our model closely resembles a recently established model of resistance exercise in which mice pull a loaded cart in horizontal plain (Zhu et al, 2021). This model also showed hypertrophy in the plantaris muscle but not in the gastrocnemius.…”

“…In our model, there is no direct handling of the rat during the exercise sessions. In contrast, the weight pulling mouse model of (Zhu et al, 2021), and the ladder climb model require repeated handling of the animals at the end of each run and placing them at the starting point. This repeated handling likely causes an additional stress.…”

Influence of weighted downhill running training on serial sarcomere number and work loop performance in the rat soleus

“…This distinction in training stimuli was offered previously as explanation for observations of only small adaptations in rat soleus SSN and mechanical function following downhill running training ( Chen et al, 2020 ). Larger magnitude changes in muscle architecture and strength in animals following 3 days/week training programs support this perspective as well ( Butterfield and Herzog, 2006 ; Ochi et al, 2007 ; Zhu et al, 2021 ).…”

“…Previous models of eccentric-biased resistance training in rats, rabbits, and mice optimised muscle architectural adaptations with lower compared to higher training frequencies ( Butterfield and Herzog, 2006 ; Morais et al, 2020 ; Ochi et al, 2007 ; Wong and Booth, 1988 ; Zhu et al, 2021 ), so rats ran 3 days per week (Monday, Wednesday, and Friday). Rats ran on an EXER 3/6 animal treadmill (Columbus Instruments, Columbus, OH, USA) set to a 15° decline.…”

Role of macrophages during skeletal muscle regeneration and hypertrophy—Implications for immunomodulatory strategies

“…Although an increased number of macrophages was reported in the absence of histological alterations after electrically‐evoked concentric contractions (McLoughlin et al, 2003 ), the impact of the corresponding experimental protocols on muscle mass (that would have defined hypertrophy) was not documented. On that basis, the use of newly developed mouse models of exercise‐induced muscle hypertrophy relying on weight pulling mimicking resistance exercise in human (Zhu et al, 2021 ) or neuromuscular electrical stimulation‐induced myonuclear accretion (Zavoriti et al, 2021 ) could be particularly relevant to decipher the role of macrophages in this context.…”