By Sally Solo |

(FORTUNE Magazine) – With swimming, basketball, and other indoor sports maxed out in popularity, what will recreational athletes do next? Take a hike. Or a camping trip. Kurt Salmon Associates, a consulting firm, predicts that equipment and apparel sales for cycling, roller blading, and other outdoor sports will grow 4% to 5% annually through the rest of the decade, compared with no growth for indoor sports such as racquetball. Fresh air appeals to baby-boomers with children as well as to environmentalists. Former joggers who exercise indoors to spare their battered joints may venture outside again for variety. Says Christian van Dyke, marketing director of Nike's new outdoor division: ''Outdoor fitness is as well suited for New York City as it is for Salt Lake City.'' Sporting goods companies have heard the call of the wild. In addition to introducing its new element-resistant shoes, Reebok International may tie up with ski resorts to organize summer mountain bike tours. Nike plans to spend more than $10 million this year to promote outdoor cross-training. Coleman Outdoor Products, best known for its lanterns and other camping gear, increased revenues 20% to $353 million last year and almost doubled earnings.