Training of intramuscular connective tissue in elderly

Background The aging process is accompanied by losses in skeletal muscle mass and function, where strength losses are typically larger than those in muscle mass. Changes in the structure and composition of intramuscular connective tissue (IMCT), which is responsible for force transmission within muscles, may represent an important but overlooked factor accounting for this loss of muscle quality. Current exercise-based treatment approaches may not incorporate adequate stimuli to induce IMCT renewal. Aims and hypotheses The aim of this project is to test the potential of various forms of physical exercises in stimulating the renewal of IMCT in lower limb muscles of senior people. A novel resistance training regimen will be developed by incorporating exercises specifically stimulating the IMCT into a training program as conventionally prescribed for the treatment of age-associated muscle weakness. We hypothesize that the regular execution of jumps in combination with weight training will lead to superior strength gains as conventional weight training alone. Originality Studying exercise modalities to target the IMCT, our project will be the first to test the effectiveness of different training stimuli in inducing regeneration of non-functionally active muscle tissue. Thus, it adopts a new approach to the treatment of age-associated muscle function deficits. Study design and methods This project will be carried out in 2 phases. In Phase 1, we will compare 4 different exercises targeting thigh and calf muscles (A: Conventional weight training, B: Weight training assisted by foam rolling, C: Weight training using only lengthening muscle contractions, D: Jumps) to identify the single one demonstrating the greatest potential to induce IMCT rejuvenation. This will be accomplished through the analysis of the activity of genes associated with IMCT cell turnover in tissue samples extracted from the thigh after an acute training session consisting of the above-mentioned exercises. Phase 1 will be completed in a sample of 24 men aged 65-70 years. For Phase 2, we will then proceed to design an innovative training program by incorporating the exercise specifically stimulating the IMCT (identified in Phase 1) into a standard training program as typically prescribed for elderly cohorts. 28 subjects (equal number of men and women, aged 65-70 years) each will be assigned to groups training according to this novel, IMCT-specific program, conventional training recommendations, or a non-training control group. Following 4 months of training, the effectiveness of the different interventions will be compared based on histological (gene and protein analyses), imaging-based (muscle volumes, structure and density) and functional tests (e.g., strength measurements, walking speed, hand grip strength).

As we age, our skeletal muscles not only experience a gradual loss of strength and mass but also become progressively infiltrated with connective tissue. This fibrosis can lead to reduced muscle flexibility and increased susceptibility to injury. While conventional exercise regimens for older individuals are effective at maintaining or restoring muscle strength, they often have limited impact on the composition of muscle tissue. In response to this challenge, our project, titled "Training of Intramuscular Connective Tissue in Older Age," set out to discover suitable forms of physical training capable of stimulating the intricate network of connective tissues within muscles and promoting cellular rejuvenation. To achieve this objective, we conducted a two-phase study. In the first phase, we investigated how various training modalities, including conventional strength training, strength training with eccentric muscle work, jump training, and self-myofascial release using the Black Roll, influenced the activity of genes associated with connective tissue cell renewal. The results from this initial phase pointed to jump training and Black Roll myofascial release as the most promising methods for stimulating intramuscular connective tissue. Subsequently, we integrated these targeted training stimuli into a four-month program that combined conventional strength training with exercises designed to specifically activate connective tissue. This innovative training program was compared to traditional strength training in terms of its impact on muscle strength, mass, and structure. The findings from the training study revealed that both the conventional and novel training programs led to significant improvements in muscle strength, with no discernible differences between them. However, noteworthy increases in thigh muscle size and structural changes were only observed in the group following the novel training program. Further examinations of muscle samples in subsequent studies will shed light on whether our developed training regimen can indeed bring about enduring alterations in the structure, composition, and mass of the connective tissue within trained muscles over the course of extended training.