Aerobic, resistance exercise while in space preserves heart function in zero gravity
Click Here to Manage Email Alerts
Key takeaways:
- Routine aerobic and resistance training may prevent cardiac atrophy while in space.
- Countermeasure exercise was effective in preserving heart function despite reduced cardiac work during spaceflight.
Aerobic and resistance exercise routines were observed as effective countermeasures to change in heart function that occurs during prolonged time in space, researchers reported.
Astronauts aboard the International Space Station (ISS) — and other space travelers who experience prolonged time in microgravity — may be able to stave off cardiac atrophy caused by spaceflight with routine exercise, according a study published in the Journal of the American College of Cardiology.
Image: Adobe Stock
“Gravitational and hydrostatic gradients play essential roles in determining the distribution of pressure and volume within the cardiovascular system. When these gradients are removed or minimized, such as during space flight or its ground-based simulations (bed rest), a central fluid shift occurs, initiating a neurohumorally mediated reduction in blood/plasma volume,” Shigeki Shibata, MD, PhD, of the Institute for Exercise and Environmental Medicine at Texas Health Presbyterian Hospital and University of Texas Southwestern Medical Center, and colleagues wrote. “Compounding these hemodynamic changes is a reduction in physical activity associated with confinement ... Within a few weeks of real or simulated microgravity, the heart appears to atrophy, presumably in response to reduced myocardial work.”
Therefore, Shibata and colleagues sought to evaluate whether current exercise countermeasures participated in by astronauts on the ISS successfully offset cardiac atrophy during prolonged time in space.
The exercise countermeasures consisted of at least 1.5 hours of exercise 6 days per week and included 30 to 45 minutes of aerobic training and 60 to 75 minutes of resistance training.
For this study, the researchers measured LV and right ventricular (RV) mass and volume in 13 astronauts (mean age, 49 years; 4 women). Twenty four-hour ambulatory BP, activity and cardiac MRI were done between 75 and 60 days preflight; 24-hour ambulatory BP and activity were measured 15 days before landing; and another cardiac MRI was done 3 days after return to Earth.
The average stay aboard the ISS was 155 days.
Change in heart function in spaceflight
The researchers reported that total cardiac work was lower during space flight (P = .008) but observed no significant difference in mean LV mass postflight compared with preflight (preflight, 115 g; postflight, 118 g; P = .053) and marginally higher postflight LV stroke volume (P = .074) and EF (P = .075).
In addition, RV mass (P = .999), RVEF (P = .147) and ventricular end-diastolic (P = .934) and end-systolic volumes (P = .145) were also not significantly different postflight compared with preflight, according to the study.
Moreover, the researchers reported positive correlations between the change in LV mass and relative change in total cardiac output (r = .73; P = .015) and total cardiac work (r = .53; P = .112).
“In contrast to predictions from prolonged sedentary bed rest, likely because of acute and regular loading during countermeasure exercise inflight, cardiac atrophy was not evident in either the left or right ventricle after prolonged space flight,” the researchers wrote. “These data suggest the current exercise countermeasures used on the ISS are effective at maintaining ventricular morphology, despite the reduction in overall cardiac work during spaceflight.”
‘Unique solutions’ needed for space-related medical problems
In a related editorial, Carl L. Tommaso, MD, interventional cardiologist at Baylor Scott and White–Temple in Temple, Texas, discussed the findings and how additional problems requiring unique solutions will continue to present themselves as humans continue to pursue deep space exploration.
“Although there is no control group, surrogate controls such as prolonged bed rest suggest that cardiac mass may be reduced by 1% per week while in space. At this rate, any prolonged space mission would severely affect cardiac function and cause significant disability upon returning to 1g,” Tommaso wrote. “The described countermeasures demonstrate preservation of cardiac mass and function with little disability upon returning to earth. The authors also noted a progressive increase in left atrial size, which may predispose to atrial arrhythmias during prolonged space flight.
“So, as we excitedly await the further exploration of space, we also await the medical problems caused by the altered physiological response and unique solutions that will be necessary,” he wrote. “‘To go boldly where no man has gone before’ certainly describes the human mission to Mars and further deep space exploration.”
Reference:
Collapse
Click Here to Manage Email Alerts