Kathleen Grenier is no stranger to the Boston Marathon but this year, rather than shouting words of encouragement from the sidelines, she’ll be in the trenches.The English High and Salem State graduate will join thousands of others in waging war on Heartbreak Hill and all the other peaks and valleys along the 26.2-mile route that conspire against even the most determined runner.Grenier, who grew up in Lynn but now lives in Peabody, has been running for about five years. She was content doing small races until a year or so ago when her grandfather, Michael DeJoy, suffered a stroke in her home. The desire to challenge herself and at the same time raise money for a cause dear to her heart (the American Stroke Association) prompted Grenier to tackle the Marathon.”I’ve gone to the Marathon in the past (as a spectator), but I wanted to do it myself because it’s such a challenge. When my grandfather had the stroke, that’s what really pushed me,” Grenier said.Grenier said that what has always impressed her from a spectator standpoint has been the odds some of the marathoners, like the father-son team of Dick and Rick Hoyt, have overcome. Dick Hoyt has been running the Marathon for more than 25 years while pushing his son, Rick, in a wheelchair.”I’ve always been on the other side of the fence watching people (like the Hoyts) and I think it’s amazing,” Grenier said. “I figured I should be on the other side running it.”Grenier said she didn’t participate in athletics in high school (she graduated from English in 1999), but she started running with friends for fun and exercise. Although she lives in Peabody now, Grenier said she still enjoys runs around Sluice and Flax ponds in Lynn as well as along the beach. She sometimes starts up around the pond area and runs to the beach and back for an 8-10 mile loop. A couple of weeks ago she did a 21-mile run in preparation for the marathon and was happy with the results.”That was a big test,” she said, adding that she’s aiming for a time of about 4:20 in the marathon.Preparing for next Monday has been a bit of a challenge in recent weeks because Grenier just started a new job with AT&T and has been shuttling back and forth between Massachusetts and Connecticut for work training. The 2003 Salem State graduate worked in print and online advertising for Verizon for six years before getting her new job, also in online advertising, at AT&T. When she’s not running, Grenier finds plenty to keep her busy. She’s also into kickboxing and enjoys skiing, mountain biking and playing the piano.Grenier said she’ll have plenty of family members cheering her on along the way and her father, Raymond, who plans to join her for the final few miles and her mother, Kathy, who will be at the finish line. Her grandfather, who she said has worked very hard over the past year or so to get his strength and mobility back, will also be rooting for her.Grenier has a website (http://sites.google.com/site/kathleenrun4americanstroke/home) that includes information on how to donate to the American Stroke Association.”He (her grandfather) has inspired me in many ways from when I was a child all through growing up,” Grenier wrote on her website. “I will always have a special place in my heart for him.”