Altered trunk and lower extremity movement coordination after neuromuscular training with and without external focus instruction: a randomized controlled trial

Background This study sought to determine the effects of a 6-week neuromuscular training (NMT) and NMT plus external focus (NMT plus EF) programs on trunk and lower extremity inter-segmental movement coordination in active individuals at risk of injury. Methods Forty-six active male athletes (controls = 15, NMT = 16, NMT plus EF = 15) participated (age = 23.26 ± 2.31 years) in this controlled, laboratory study. Three-dimensional kinematics were collected during a drop vertical jump (DVJ). A continuous relative phase (CRP) analysis quantified inter-segmental coordination of the: (1) thigh (flexion/extension)—shank (flexion/extension), (2) thigh (abduction/adduction)—shank (flexion/extension), (3) thigh (abduction/adduction)—trunk (flexion/extension), and (4) trunk (flexion/extension)—pelvis (posterior tilt/anterior tilt). Analysis of covariance compared biomechanical data between groups. Results After 6 weeks, inter-segmental coordination patterns were significantly different between the NMT and NMT plus EF groups (p < 0.05). No significant differences were observed in CRP for trunk-pelvis coupling comparing between NMT and NMT plus EF groups (p = 0.134), while significant differences were observed CRP angle of the thigh-shank, thigh-trunk couplings (p < 0.05). Conclusions Trunk and lower extremity movement coordination were more in-phase during DVJ in the NMT plus EF compared to NMT in active individuals at risk of anterior cruciate ligament injury. Trial registration: The protocol was prospectively registered at UMIN_RCT website with ID number: UMIN000035050, Date of provisional registration 2018/11/27. Supplementary Information The online version contains supplementary material available at 10.1186/s13102-021-00326-9.


Appendix B: Single-Leg Lateral Progression
The trainer instructs the athlete to begin and end each hop hold with deep knee flexion, avoiding excessive nonsagittal plane motion of the lower extremities and trunk during take-o ff and landing. In the later phases, the athlete should also be instructed to minimize the amount of rebound (or reverberation) of the BOSU under the foot. Phase 4 should incorporate lateral and medial jumping.

Appendix C: Lunge Progression
The trainer instructs the athlete to maintain most of the weight on the lead leg as they lunge forward into a deep knee extension, avoiding hyperextension of the trunk. A slight forward lean is acceptable, as this will assist the individual to drive off the lead leg. The athlete's knee should never advance beyond the ankle during the exercise. The clinician should also cue the athlete to avoid pausing between the lunge and upright portions of the task.

Appendix D: Tuck Jump Progression
The trainer instructs the athlete on the proper countermovement preparation (slight crouch downward, extending arms behind body) prior to the vertical jump. The vertical jump begins as the athlete vigorously swings the arms forward as they jump straight up, pulling their knees up as high as possible. The goal is to achieve a parallel position of both thighs in relation to the floor and to use a toe-to-midfoot rocker landing upon descent into a deep-knee flexion hold. As the athlete progresses from 2 consecutive jumps (phase 2) with proper technique to multiple consecutive jumps (phase 3), the clinician instructs the athlete to avoid excessive non-sagittal plane motion of the lower extremities and trunk, and to try to take off and land in the same footprint in which the task started. Tuck jumps performed over an object should be completed only if the athlete completes repeated phase 3 jumps with proper technique. The goal of this exercise is to focus on minimizing the frontal plane motion of the trunk and lower extremities during lateral jumping. The height of the jump is not the focus; rather, increasing speed with good technique is the criterion by which the athlete will be progressed to the next phase. A deep-knee flexion position is emphasized upon each take-off and landing, regardless of phase. The clinician should encourage the athlete to jump "close to the line" in preparation for quicker lateral movements. This exercise is progressed from double leg (phases 1 and 2) to single leg (phases 3 and 4) once the athlete can demonstrate symmetrical timing and proper alignment with single-(phase 1) and then repeated double-leg landing (phase 2).

Appendix F: Lateral Trunk Progression
The trainer provides stabilization at the pelvis and lower extremities throughout the phases. The trainer instructs the athlete to bend laterally at the waist during the crunch movement and avoid non-frontal plane motion of the trunk. The athlete should also maintain the arms in a crossed position over the chest, except when involved in a partner tossand-catch activity. Progression should be implemented when the athlete can complete the current phase with proper form and full trunk motion.

Appendix G: Prone Trunk Stability
The trainer instructs the athlete to minimize the amount of rebound (or reverberation) of the BOSU under the trunk, especially during partner perturbations. As the athlete progresses to the prone bridge position (phases 3 and 4), the 2 to 3 contact points away from the center of mass further destabilize the athlete as they alternate extremity limb positions. The goal is to avoid excessive trunk rotation and flexion or hyperextension as they lift their limbs.

Appendix I: Posterior Chain Progression
The trainer instructs the athlete to avoid lumbar hyperextension during the bridging-task phases. Manual and verbal cues may be necessary to acclimate the athlete to a neutral pelvic position during this exercise, avoiding contralateral hip drop. As the athlete advances through stages, the goal is to perform full, uncompensated motion. Phase 3 is designed to narrow the base of support and the number of contact points to increase the difficulty of the task. In phase 4, the athlete should be instructed to minimize motion of the ball under their feet while achieving controlled hip flexion and extension. The key component to this exercise progression is the ability of the athlete to minimize trunk deviation in the frontal and transverse planes while avoiding excessive co-contraction of the muscles of the lower extremities. The trainer instructs the athlete to keep the muscles of the standing leg relaxed, with the knee slightly flexed and toes and foot relaxed. Hip hinging with an erect spine should be emphasized throughout the phases.

Appendix K: Lunge Jump Progression
This is a plyometric advancement of the lunge progression in appendix A, and the same emphasis should be placed on the mechanics of the lead leg and trail leg, as well as the trunk. The trainer instructs the athlete to maintain more weight toward the lead limb to generate adequate power for the jump and maintain balance. The trainer instructs the athlete to descend into a deep-knee flexion hold upon each jump take-off and landing, avoiding excessive non-sagittal plane motion of the lower extremities and trunk. Keep the bar horizontal. Stand on 1 leg and reach slowly towards the cone with your knee while bending your knee.
Jump as far as you can, while jumping, focus on jumping as close to the cone as possible.
Single leg hop for distance Lunge slowly at an even pace while pretending like you are having a plank on your back point your knee towards an imagery point in front of you / reach slowly towards the cone.