For those looking to find strong Medical stocks, it is prudent to search for companies in the group that are outperforming their peers. Has Select Medical Holdings (SEM) been one of those stocks this year? Let's take a closer look at the stock's year-to-date performance to find out.Select Medical Holdings is one of 1024 individual stocks in the Medical sector. Collectively, these companies sit at #15 in the Zacks Sector Rank. The Zacks Sector Rank includes 16 different groups and is listed in order from best to worst in terms of the average Zacks Rank of the individual companies within each of these sectors.The Zacks Rank is a proven system that emphasizes earnings estimates and estimate revisions, highlighting a variety of stocks that are displaying the right characteristics to beat the market over the next one to three months. SEM is currently sporting a Zacks Rank of #1 (Strong Buy).Over the past three months, the Zacks Consensus Estimate for SEM's full-year earnings has moved 47.35% higher. This signals that analyst sentiment is improving and the stock's earnings outlook is more positive.Based on the latest available data, SEM has gained about 24.80% so far this year. Meanwhile, stocks in the Medical group have gained about 1.12% on average. As we can see, Select Medical Holdings is performing better than its sector in the calendar year.To break things down more, SEM belongs to the Medical - HMOs industry, a group that includes 10 individual companies and currently sits at #157 in the Zacks Industry Rank. Stocks in this group have gained about 5.83% so far this year, so SEM is performing better this group in terms of year-to-date returns.Investors with an interest in Medical stocks should continue to track SEM. The stock will be looking to continue its solid performance.Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Select Medical Holdings Corporation (SEM): Free Stock Analysis Report To read this article on Zacks.com click here.