Exercise Responses to Gravity-Independent Flywheel Aerobic and Resistance Training

Abstract

Background Although a number of exercise systems have been developed to mitigate the physiological deconditioning that occurs in microgravity, few have the capacity to positively impact multiple physiological systems and still meet the volume/mass requirements needed for missions beyond low earth orbit. The purpose of this study was to test the gravity-independent Multi-Mode Exercise Device (M-MED) for both resistance (RE) and aerobic (AE) training stimuli. Methods Eight men and nine women (mean age 22.0±0.4 years) completed five weeks of training on the M-MED: RE 4×7 squats two days a week, and AE 4×4-min rowing bouts at ~90% VO2max three days a week. Pre- and post-training data collection included an aerobic capacity test, MR imaging, strength testing, and vastus lateralis muscle biopsy. Results VO2max increased 8%, 3RM strength 18%, and quadriceps femoris cross-sectional area (CSA) 10%. Knee extensor strength increased at all isokinetic speeds tested. Subjects also demonstrated improved resistance to fatigue in knee extension. At the cellular and molecular level, the biopsy revealed increases in mixed myofiber CSA (13%), citrate synthase activity (26%), total RNA concentration (24%), IGF-I mRNA (77%), Type IIa Myosin Heavy Chain (MHC) mRNA (8%), and concomitant decrease in Type IIx MHC mRNA (−23%). None of the changes were gender-specific. Discussion Both the functional outcomes and biomarker changes indicate that a very low volume of M-MED exercise results in robust adaptation in the cardiovascular and musculoskeletal systems. The M-MED has the potential to provide a wide range of countermeasure exercises and should be considered for testing in ground-based spaceflight simulation.

Effects of Flywheel Training on Strength-Related Variables: a Meta-analysis

“…The results from this meta-analysis also show that younger individuals (< 39 years old) [2, 6, 12, 15, 26, 27, 34, 40, 42–44, 47] seem to get greater benefits from flywheel training compared to older individuals (> 59 years old) [36, 41] (0.47% and 0.07% increase per day, respectively). This was observed even though the average number of days per intervention for the older individuals was 63 days compared with 39 days for the younger individuals and with no great difference in training frequency.…”

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Fig. 4Forest plot showing effect size comparing pre and post-test muscle cross-sectional area during a period of 5 to 8 weeks of flywheel training [15, 36, 42, 43, 47]. [+] indicates positive effect of flywheel training.

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“…The post-test was completed after 4–10 weeks of flywheel training 1–3 times per week.

Fig. 6Forest plot showing effect size comparing pre and post-test maximal strength during a period of 4 to 10 weeks of flywheel training [2, 6, 12, 15, 26, 27, 34, 36, 40–44, 47, 48]. [+] indicates positive effect of flywheel training.

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“…In the present data set, there seems to be no correlation between the number of training sessions per week and the increase of muscle CSA. The second greatest muscle hypertrophy response of 0.27% increase per day was noted in a study with only two training sessions per week during a 5-week period [47].…”

Implementing Eccentric Resistance Training—Part 2: Practical Recommendations

“…Specifically, the authors recommended that FIT should be performed with four sets of seven repetitions with 90–180 s of rest between sets, no more than twice per week with 48 h of recovery between sessions. While this set and repetition scheme may vary from TRT, the majority of FIT studies have used this protocol [ 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ].…”