Planet Fitness Inc. shares declined in the extended session Tuesday after the gym chain reported in-line earnings and an outlook that was slightly lower than the Wall Street consensus. Planet Fitness shares slipped 4% after hours, after declining 1.9% to $40.65 in the regular session. The company reported first-quarter net income of $19.9 million, or 23 cents a share, compared with $8.8 million, or 14 cents a share, in the year-ago period. Adjusted earnings were 27 cents a share. Revenue rose to $121.3 million from $91.1 million in the year-ago period. Analysts surveyed by FactSet had estimated 27 cents a share on revenue of $115.6 million. For the year, Planet Fitness expects revenue to rise 20% from the previous year. Analysts expect revenue of $522.9 million, or an increase of 22%.