Activities Sports & Athletics The Best Butterfly Core Training Swimming Exercises Share PINTEREST Email Print PeopleImages / Getty Images Sports & Athletics Swimming & Diving Workouts Gear Health & Safety Technique Diving Baseball Basketball Bicycling Billiards Bodybuilding Bowling Boxing Car Racing Cheerleading Cricket Extreme Sports Football Golf Gymnastics Ice Hockey Martial Arts Professional Wrestling Skateboarding Skating Paintball Soccer Table Tennis Tennis Track & Field Volleyball Other Activities Learn More By Gary Mullen Gary Mullen is a world-renowned swimming expert, writer, and speaker. He is a member of the advisory board of the International Society of Swim Coaches. our editorial process Gary Mullen Updated May 01, 2018 For years, swimming coaches and trainers only taught sit-ups, crunches, and leg lifts, but the state of swimming core training is outdated, which leads to reduced performance and increased injury. While this course of training was standard practice in the 1970s, it simply isn't up to par these days. Luckily, it isn't too late to improve your core training theory for swimmers from a training perspective. By providing specific core training exercises, you'll help swimmers activate their core, then integrate it with their arms and legs. Here are three hard butterfly core training exercises for those looking to protect their spine, while still developing spinal flexion strength. 01 of 03 Bosu Curl-Up FatCamera / Getty Images Having eccentric control of a movement is key to reducing spinal stress and increasing strength. The eccentric phase is when a muscle is lengthened. The Bosu ball allows a greater eccentric range of motion, focusing greater force production and control of movement. Exercise Steps Lie with your back on a Bosu ball with knees bent.Lock your fingers together over your head.Brace your abdominals before initiating movement.Do a curl-up, until the bottom of the shoulder blades come off the floor.Keep abdominals tight and back flat at all times. (There may be an instinctual feeling to arch your back as you lift, but don't give in to it.) 02 of 03 Hands Over Head Curl-Up With Partner Pulls Westend61 / Getty Images Integrating the core with the legs plays a critical role in the butterfly stroke. Unfortunately, many swimmers simply don't emphasize the legs during their activation. This exercise helps strengthen the back of the legs (the hamstrings) while improving spine flexion strength. Exercise Steps Lie on your back with knees bent.Brace your abdominals.Lock your fingers together over your head.Flatten back before initiating movement.Have a partner pull on your heels, attempting to straighten your leg (do not let them straighten your legs).Do a curl-up, until the bottom of the shoulder blades come off the floor.Keep abdominals tight and back flat at all times. (There may be an instinctual feeling to arch your back as you lift, but don't give in to it.) 03 of 03 Kneeling Pallof Press with Extension Medioimages/Photodisc / Getty Images The last step is integrating the arms, core, and legs. This exercise requires shoulder stabilization, spine flexion strength, and quadriceps strength. When done properly this trifecta creates a challenging, but safe form of spinal flexion strengthening. Exercise Steps Securely set up a band head height while kneeling.Next, kneel on a mat and face away from the band.Brace your abdominals, lean back, then raise your arms overhead and slowly return upright.Lower the arms, then repeat. Remember -- don't let your body arch.