有劲 (yǒu jìn) has two distinct meanings: 'energetic/vigorous' (about a person's physical or mental energy) and 'interesting/fun' (about an activity or thing). As 'energetic', it is more colloquial than 积极 (jī jí 'proactive, positive attitude') and less intense than 起劲 (qǐ jìn 'enthusiastic, with gusto'). As 'interesting', it is a spoken alternative to 有趣 (yǒu qù) and 有意思 (yǒu yì si), all very close in meaning.