Several people working in the nonunion Tesla electric car factory in Fremont, Calif., say long hours, low wages, poor training and an ambitious production schedule have led to serious injuries and, in some cases, permanent disabilities. The workers also say the company frequently violates its own labor policies, a claim Tesla denies.

Employee engagement is a hot topic, but too much can lead to symptoms of burnout, researchers said. Generally, they found workers who were optimally engaged had high resources but low work demands, in terms of workload, bureaucracy, concentration and attention, while those who were "engaged-exhausted" had high resources and high work demands.

Wages rose 2.9% in January compared with the same time last year, the highest growth since June 2009, according to the Labor Department. Unemployment stayed at 4.1%.

Some restaurants and other businesses plan to allow employees to watch parts of major sporting events such as the Super Bowl and the Winter Olympics. Flexibility makes sense, as companies are "not going to be able to stop people's excitement," says attorney Philippe Weiss.