The most significant ways you can improve how you ride a wave, apart from surfing itself, is to improve your upper spine and hip mobility, trunk rotation strength, anti-rotation strength, hip and leg strength, and power.
Rotational (or rotatory) core training is an underrated aspect of a good surf strength and conditioning program. Rotatory training can help you perform more powerful turns, as much of surfing maneuvers involve a dynamic upper spine. Having the capacity to safely generate more force through your hips, trunk, and shoulders is really important, as rotation training is not just about twisting as hard as you can, and in fact can be very dangerous.
Learning how to decelerate rotational forces is a huge component of a well-structured strength program. Absorbing rotational forces through the core and hips, rather than compensating though your lower back, is an essential skill to learn for anybody, let alone surfers.
Studies have shown that surfing athletes that exhibit greater lower-body isometric and dynamic strength also perform higher scoring turning maneuvers during wave riding.
Training for strong, powerful hips (glutes) and legs has benefits way beyond better surfing. Single leg training is a great way to develop ankle-knee-hip-core stability, balance, and strength. Hip strength helps prevent strain and injury to your knees and lower back, and also gives you a (firm) ass.
*The video above demonstrates 5 of my top mobility/strength exercises for stronger, more powerful and efficient surfing.
Skater to Curtsy Squat (to strengthen your glutes, hamstrings and quads from multiple angles)
The more you lean forward and stick your hips back, the more you will target your glutes and hamstrings. Keeping a neutral spine, squat on one leg and slide the other foot out to the side, back and then crossed behind your body. Ensure there is no weight placed on the sliding foot and keep the squatting knee over your toes throughout. Repeat this sequence four more times. This can be challenged by holding a free weight or wearing a weighted vest, but typically five reps (one rep = leg to the side + back + crossed) are hard enough when performed correctly. You can place an ice cream lid or piece of cardboard under your sliding foot.
Step Back and Curtsy Squat.
This is a little more advanced than the previous exercise. Choose a step which is close to knee height. Keep a neutral spine, bend from your hips and squat on one leg while extending your free leg behind your torso to gently tap your foot to the floor. Keep your weight off the tapping foot. Stand up again and then squat while crossing you leg behind and to the side of your torso (curtsy squat). Repeat this sequence four more times. It is super important to keep your squatting knee tracking over your toes throughout, especially in the curtsy part of the squat.
Single Leg Hip Bridge (to get stronger glutes, improve pelvic stability and hip strength)
Lie on your back and place one foot on a bench and lift your other knee to your chest. Use your glutes to extend your hips up. Make sure you are extending at your hips, not your lower spine, by rotating your hip bones back to keep your lower back flat. Push through your heels to activate your glutes. 10-15 reps per side is a good challenge, and you can elevate your foot (eg. use the side of your bed or couch arm rest) to make it harder.
Russian Twist for rotational and anti-rotational trunk strength
Sit on a small Swiss ball and then roll out so that your head and upper back are in contact with the ball. Bridge your hips up using your glutes and abs to keep your lower back flat. You can either do this using bodyweight only or you can hold a dumbbell with both hands, keep your arms straight, and slowly rotate your chest to face the side. The key is to to keep both hip bones facing the sky throughout the exercise and to keep your lower back flat by using your glutes to pull your hip bones backward. You will then be rotating your upper spine and keeping your hips relatively still. The bodyweight version is a little more on the rotational strength side and the dumbbell version is a little more on the anti-rotational strength side. I like to train both.
Squat Rotation (for rotational and anti-rotational trunk strength)
I thought of this exercise after looking at overhead pictures of my snowboarding and surfing clients. Surfers and snowboarders need to squat and rotate their torso, lifting one arm in the air and grabbing the board with the other. The Squat Rotation exercise itself does not demonstrate how we would want to look in the water, but it serves a purpose in strengthening core rotation from a squat position and controlling excessive hip shift and knee drop. Set the cable handle high (you could also use a stretchy power-band if you do not have a cable machine) and stand side-on to the cable machine. Position your feet wide in a squat stance. Squat down as your rotate from your waist, aiming to keep your hips completely still and doing all the rotating from your upper spine. You will automatically want to shift your hips toward the side that you are rotating and drop your knee inward that is closest to the cable machine. Do your best to keep your hips in the center and keep both knees over your toes. Aim to touch your hand (holding the cable) to your outside big toe as you reach your opposite arm up (this trains the rotational core strength) and slowly return to the center (this trains the anti-rotational core strength). Repeat for 10 reps per side. Your spine should stay military straight as you squat.
*In the water, you would not try to keep your back knee over your toes and would allow your hips to shift. The purpose of these strength and conditioning exercises are to practice a more balanced, optimal form to give your body the posture, stability, and strength foundations it needs for the imperfect form of surfing.
For more surf strength and conditioning and programs that you can follow from anywhere in the world, with or without training equipment, head to surfstrengthconditioning.com