Interesting article in 2011 in LifeScience on the effects of armor on endurance (in this instance, medieval, but many of the principles probably would hold re unpowered armor and vacc suits):
"A new study that put armor-wearing volunteers on treadmills finds that wearing a full suit of armor (which might weigh up to 110 pounds, or 50 kilograms), takes more than twice the energy of walking around unencumbered. Even lugging around a backpack of equal weight is less energy-intensive than wearing armor, the study found, because wearing 17 pounds (8 kg) of steel plates on each leg requires no small amount of extra exertion. ...He and his colleagues recruited four volunteers, historical re-enactors who were accustomed to wearing their own sets of replica 15th-century armor. Each man agreed to walk and run on a treadmill (a task Askew called, "very clanky") while wearing a breathing mask to measure how much oxygen they took in and how much carbon dioxide they excelled, as well as their breathing rate. These measurements allowed the researchers to calculate the energy they used during the exercise periods."
"The modern-day knights used 2.1 to 2.3 times more energy walking with their armor on compared with walking without it. Running with armor took 1.9 times the energy as running armor-free. The result, Askew said, is that men in armor end up moving much more slowly than men without armor. This effect is only exacerbated with age: At his maximum aerobic capacity, an average 38-year-old man could cover about 5.5 feet (1.7 meters) per second, compared with 8.8 feet (2.7 m) per second for an unarmored 38-year-old. With a maximum walking speed of 4.6 feet (1.4 m) per second, an armored 55-year-old would have trouble keeping up. The research also gives a hint into how fit the knights of old must have been. Although modern soldiers lug around equipment as heavy as a knight's armor, Askew said, they expend less energy doing so because their legs are unencumbered."
"It requires a great deal of physical exertion to even perform a medium-speed walk in a suit of armor," Askew said. "I certainly don't think you'd be able to put on a suit of armor and walk around with it without suffering quite badly if you weren't used to it."