Vigor was one of John F. Kennedy’s favorite words, pronounced in his much-parodied Boston accent as “vig-ah.” He used the word frequently while running for president in 1960, to highlight his youth and energy and to contrast him with President Dwight Eisenhower, who was 70 and had suffered a heart attack in office. As president, JFK famously played touch football and encouraged his aides to take 50-mile hikes. But Kennedy was less vigorous than he pretended. His back, injured in World War II, was a source of constant pain, and he suffered from Addison’s disease, an adrenal gland disorder that causes fatigue and muscle weakness. As Peter Carlson reports in our cover story, “Jack Kennedy and Dr. Feelgood,” Kennedy’s painful ailments led him to turn to a dubious doctor named Max Jacobson, who supplied synthetic vigor in the form of amphetamine-laced “vitamin shots.” The result was a president who was high on speed at a critical summit meeting with Soviet Premier Nikita Khrushchev 50 years ago this month.