High-Intensity Jump Training Is Tolerated during 60 Days of Bed Rest and Is Very Effective in Preserving Leg Power and Lean Body Mass: An Overview of the Cologne RSL Study

Abstract

PurposeSpace agencies are looking for effective and efficient countermeasures for the degrading effects of weightlessness on the human body. The aim of this study was to assess the effects of a novel jump exercise countermeasure during bed rest on vitals, body mass, body composition, and jump performance.Methods23 male participants (29±6 years, 181±6 cm, 77±7 kg) were confined to a bed rest facility for 90 days: a 15-day ambulatory measurement phase, a 60-day six-degree head-down-tilt bed rest phase (HDT), and a 15-day ambulatory recovery phase. Participants were randomly allocated to the jump training group (JUMP, n = 12) or the control group (CTRL, n = 11). A typical training session consisted of 4x10 countermovement jumps and 2x10 hops in a sledge jump system. The training group had to complete 5–6 sessions per week.ResultsPeak force for the reactive hops (3.6±0.4 kN) as well as jump height (35±4 cm) and peak power (3.1±0.2 kW) for the countermovement jumps could be maintained over the 60 days of HDT. Lean body mass decreased in CTRL but not in JUMP (-1.6±1.9 kg and 0±1.0 kg, respectively, interaction effect p = 0.03). Resting heart rate during recovery was significantly increased for CTRL but not for JUMP (interaction effect p<0.001).ConclusionParticipants tolerated the near-daily high-intensity jump training and maintained high peak forces and high power output during 60 days of bed rest. The countermeasure was effective in preserving lean body mass and partly preventing cardiac deconditioning with only several minutes of training per day.

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

“…To investigate this, we analyzed changes in myofiber CSA and the induction/prevention of myofiber type shift (slow-to-fast) in VL and SOL biopsy samples from the RSL Study using high-resolution confocal microscopy, quantitative structural capillarization parameters, combined with fiber maximal oxygen consumption (VO 2max ) estimations by optical density (OD 660nm )-based semiquantitative mitochondrial succinate dehydrogenase (SDH) histochemistry performed on freshly cut tissue cryosections. Together with previous RSL-Study reports (Kramer et al, 2017b(Kramer et al, , 2018Koschate et al, 2018;Maggioni et al, 2018;Schoenrock et al, 2018), the present investigations using muscle biopsy samples from two different functional leg muscles (prime knee extensor and deep plantar flexor) provide evidence that high-impact reactive jumps maintained myofiber size and phenotype with a trend only to also preserve oxidative capacity analyzed in the prime knee extensor VL in HDT bed rest. Nevertheless, high-impact interval training could be a short and effective exercise surrogate for multimodal/multisystem training protocols on Earth and for crew members in long-duration space missions.…”

“…This single-center, parallel-group, crossover design, and randomized controlled training study was sponsored by ESA and conducted at the German Aerospace Center (DLR:envihab human physiology facility) in Cologne. Reactive jumps in a sledge jump (RSL) system was used as countermeasure during a 6 • HDT bed rest study with n = 24 healthy male participants enrolled and randomly assigned to control [CTRL, n = 12, aged 30.0 ± 5.76 years, body mass index (BMI) 23.5 ± 2.2] or an RSL intervention group (JUMP, n = 12, aged 29.9 ± 6.6 years, BMI 23.4 ± 1.67) (Kramer et al, 2017b). One participant of the CTRL group discontinued the study 4 days before bed rest (BDC-4) for medical reasons unrelated to the study resulting in n = 11 final CTRL.…”

“…One participant of the CTRL group discontinued the study 4 days before bed rest (BDC-4) for medical reasons unrelated to the study resulting in n = 11 final CTRL. Other RSL study information, anthropometric data, participant inclusion/exclusion criteria, diet, medical and paramedical treatments are reported elsewhere (Kramer et al, 2017b). The Northern Rhine Medical Association (Ärztekammer Nordrhein) in Düsseldorf, Germany, as well as the Federal Office for Radiation Protection (Bundesamt für Strahlenschutz) Ethics Committee approved this study in accordance with the World Medical Association Code of Ethics, Declaration of Helsinki (1964).…”

“…In addition, jump training has repeatedly been shown to increase leg muscle strength (Saez-Saez de Villarreal et al, 2010) and leg stiffness (Kramer et al, 2012). Reactive jumping has the potential to prevent both musculoskeletal and cardiovascular deconditioning in disuse with minimal time expenditure and maximal training outcome (Kramer et al, 2017bMaggioni et al, 2018). Highintensity interval training with reactive jumps can also be used to preserve lean body mass and counteract cardiovascular deconditioning to a similar extent as traditional high-volume, moderate-intensity aerobic training (Kramer et al, 2017a).…”

Long-Term Microgravity Exposure Increases ECG Repolarization Instability Manifested by Low-Frequency Oscillations of T-Wave Vector

“…HDBR time period (Kramer et al, 2017), or the control group (CTRL), who did not perform any exercise. For the experiment in Toulouse, 20 male volunteers were enrolled (34 ± 7 years, 176 ± 4 cm, 73 ± 7 kg).…”