Recent studies have shown that insulin provides crucial assistance in building muscle, and that its ability to do so drops off dramatically in the elderly. Now, a study by medical researchers suggests that a simple, cost-free therapy appears to largely overcome that drop-off in insulin response: moderate aerobic exercise such as walking.

Imagine a vehicle that runs on hydrogen or biofuels and offers the same features, performance and price as today's gasoline vehicle. Will it capture half the market? Not likely, concludes a new MIT analysis of the challenges behind introducing alternative-fuel vehicles to the marketplace. Not even if it's three times more fuel-efficient.