Reactive Jumps Preserve Skeletal Muscle Structure, Phenotype, and Myofiber Oxidative Capacity in Bed Rest

Abstract

Identification of countermeasures able to prevent disuse-induced muscle wasting is crucial to increase performance of crew members during space flight as well as ameliorate patient's clinical outcome after long immobilization periods. We report on the outcome of short but high-impact reactive jumps (JUMP) as countermeasure during 60 days of 6 • head-down tilt (HDT) bed rest on myofiber size, type composition, capillarization, and oxidative capacity in tissue biopsies (pre/post/recovery) from the knee extensor vastus lateralis (VL) and deep calf soleus (SOL) muscle of 22 healthy male participants (Reactive jumps in a sledge, RSL-study 2015-2016, DLR:envihab, Cologne). Bed rest induced a slow-to-fast myofiber shift (type I ->II) with an increased prevalence of hybrid fibers in SOL after bed rest without jumps (control, CTRL, p = 0.016). In SOL, JUMP countermeasure in bed rest prevented both fast and slow myofiber cross-sectional area (CSA) decrements (p = 0.005) in CTRL group. In VL, bed rest only induced capillary rarefaction, as reflected by the decrease in local capillaryto-fiber ratio (LCFR) for both type II (pre vs. post/R + 10, p = 0.028/0.028) and type I myofibers (pre vs. R + 10, p = 0.012), which was not seen in the JUMP group. VO 2maxFiber (pL × mm −1 × min −1 ) calculated from succinate dehydrogenase (SDH)stained cryosections (OD 660 nm ) showed no significant differences between groups. High-impact jump training in bed rest did not prevent disuse-induced myofiber atrophy in VL, mitigated phenotype transition (type I ->II) in SOL, and attenuated capillary rarefaction in the prime knee extensor VL however with little impact on oxidative capacity changes.

Substantial and Reproducible Individual Variability in Skeletal Muscle Outcomes in the Cross-Over Designed Planica Bed Rest Program

“…The current analysis translated into approximately a 3-times greater number of observations compared to what is commonly found in bed rest studies (Alkner and Tesch, 2004;Trappe et al, 2007a;Blottner et al, 2020). The analyses performed indicated that the mass of the muscles involved in posture and locomotion (i.e., thigh and calf) and the function of the knee extensor muscles are the outcomes more robustly affected by bed rest, supporting previous results (Pavy-Le Traon et al, 2007).…”

“…The calf muscle area was chosen for this set of analyses because (i) it is the most consistently altered outcome measure across the studies and bed rest interventions, (ii) it is one of the outcomes with the most significant inter-individual variability, and (iii) it presents a high degree of repeatability across bed rest interventions. In addition to the observations from the current experiments, calf muscle mass is one of the most investigated outcomes in the context of bed rest (Alkner and Tesch, 2004;Trappe et al, 2007b;Salanova et al, 2015;Blottner et al, 2020). Our analyses indicated that the variability in calf muscle area changes induced by bed rest could be moderately explained by the summatory effects of all of the other variables included in the database, with "thigh muscle area, " "KE torque, "…”

Fetuin-A as a Potential Biomarker of Metabolic Variability Following 60 Days of Bed Rest

“…The results, from previous publications, show that this time-efficient countermeasure attenuated the loss of whole body lean mass, leg lean mass, V . O 2peak (Kramer et al, 2017a,b), and myofiber size and phenotype (Blottner et al, 2019). While RJT had protective effects for muscle function, it could not prevent the dysregulation of glucose and lipid metabolism.…”

Human blood adenosine biomarkers and non‐rapid eye movement sleep stage 3 (NREM3) cortical functional connectivity associations during a 30‐day head‐down‐tilt bed rest analogue: Potential effectiveness of a reactive sledge jump as a countermeasure

“…Numerous studies have evoked energy related recovery‐stress states (Nicolas & Gushin, 2015; Nicolas & Weiss, 2009), cardiovascular (Platts et al., 2009; Rabineau et al., 2020) and skeletal (Hu et al., 2014; Rubin et al., 2002) adaptation mechanisms as a reaction to microgravity. Moreover, previously documented RSL‐related adaptation trends, encountering microgravity effects, include the preservation of lean body mass, prevention of partial cardiac deconditioning (Kramer, Gollhofer, et al., 2017), the structure of the skeletal muscle, preservation of phenotype and oxidative potential of the myofibres (Blottner et al., 2020). Furthermore, extensive morphological brain changes have been observed under HDTBR conditions as a result of the redistribution of brain fluid in response to changes in gravity (Roberts et al., 2015).…”