Testing the Effect of a Plyometric Neck Training Program on Dynamic Head Stabilization in Female Rugby Players.

Plyometric Neck Training Program. Sessions will be delivered (and supervised) in the laboratory, in-person by the primary researcher, so that study groups differ only by the intervention being evaluated. Depending on the stage of training (i.e., what session volume and intensity the participant is at), sessions will last between 30 and 60 minutes). Given that the training will take place in the lab, under the supervision of the researcher, no protocols will be in place to manage adherence. Plyometric training protocol The plyometric training intervention will span 8 weeks, with 2 training sessions completed per week. The program will involve only two different exercises, each with multiple variations/levels of intensity. Wall rebounds Variation 1 Participants will begin with the middle part of their feet 40cm from the vertical line of the wall-mounted pad and force plate; they will be leaning back or forward, with either the back of their head or their forehead resting against the padding (depending on whether it is a flexion or extension set). Their hands will be crossed over their chest. They will then use their neck musculature to push their head against the padding and propel themselves away as quickly as possible; they may need to take some steps to regain their balance afterwards. Variation 2 Participants will begin with the middle part of their feet 30cm from the vertical line of the pad. They will be standing upright, and will slowly lean towards the pad so that their head moves towards it, keeping their body straight (no bend in the knees or hips), and their hands by their sides. The moment their head (either the back of the head or forehead) makes contact with the pad, they will use their neck musculature to propel themselves away as quickly as possible, aiming to minimising pad contact time and maximise force. Variation 3 The same as variation 2, but beginning 40cm away. Variation 4 The same as variations 2 & 3, but beginning 50cm away. Wall rebounds: progression and programming In session 1, participants will complete 2 sets of 5 repetitions of wall rebounds: Variation 1 in each movement pattern (flexion and extension), with 10 seconds separating each repetition, and a 2 minute rest in-between sets. So, this will total 10 contacts per movement pattern, and 20 contacts on the pad overall in session 1. If the participant completes session 1 with proper technique, and does not experience any adverse events (such as headaches, severe neck pain) during, or in the 72 hours following session 1, then session 2 will involve 3 sets of 6 repetitions for each movement pattern (therefore, a total of 36 contacts on the pad). From thereon in, progression will be informed by measures of force-time variables from the force plate and LabChart software. When researchers observe that a participant has achieved a 5% decrease in contact time on the pad since beginning that variation, the participant will progress to the next level of intensity in the following session. If a participant is progressed to Variation 4 of one or both movement patterns, and continues to achieve 5% decreases in contact time in that exercise, then further progression for that exercise will be achieved by increasing the number of repetitions per set by 1. Sling head-drops Once positioned on the table with their head resting in the sling, participants will be instructed that the sling will be released at any time in the next 10 seconds. For neck flexor trials, they will be told to begin in a crunch position (i.e., a half sit-up), letting the sling take the weight of their head, and to react to the removal of the head support by returning the head back to its original position as quickly as possible. For neck extensor trials, they will be positioned on their front, engaging the posterior chain but letting the sling take the weight of their head. A random number generator will be used to determine at which second (1-10) the researcher will trigger the release of the electromagnetic catch. This will constitute one repetition. Once the sling has been released and the participant has responded, the positioning of equipment and participant will be restored in preparation for the next repetition. Sling head-drops: progression and programming. In session 1, participants will complete 2 sets of 3 repetitions of sling head-drops in each movement pattern (flexion and extension), for a total of 12 repetitions. The rest period between repetitions will be determined by the time taken to restore the set-up. There will be a 2 minute rest in-between sets. The physiotherapy table will be fixed at the highest level of incline. As with the wall rebound exercise, there is a deliberately low volume of sling head-drops in session 1, to ensure that the participant is able to complete the exercises with proper technique, and without experiencing any adverse events (such as headaches, severe neck pain) during, or in the 72 hours following, the session. If this requirement is met, then in session 2, participants will complete 3 sets of 4 reps for each movement pattern, for a total of 24 reps. From thereon in, the incline of the table may be decreased to increase the intensity of the exercise. The timing of these incline changes will be determined by that participants progression in the wall rebound exercises; the progression in wall rebound intensity level (based on improvements in pad contact time) will be matched by a decrease in the incline of the table. As will be done for the wall rebounds, further progression beyond the last increment of intensity variations will be achieved by increases in volume (1-repetition increases per set).