Hip Muscle Strength Explains Only 11% of the Improvement in HAGOS With an Intersegmental Approach to Successful Rehabilitation of Athletic Groin Pain

Background: Exercise-based rehabilitation targeting intersegmental control has high success rates and fast recovery times in the management of athletic groin pain (AGP). The influence of this approach on hip strength and lower limb reactive strength and how these measures compare with uninjured athletes (CON) remain unknown. Additionally, the efficacy of this program after return to play (RTP) has not been examined. Purpose: First, to examine differences in isometric hip strength, reactive strength, and the Hip and Groin Outcome Score (HAGOS) between the AGP and CON cohorts and after rehabilitation; second, to examine the relationship between the change in HAGOS and the change in strength variables after rehabilitation; last, to track HAGOS for 6 months after RTP. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 42 athletes diagnosed with AGP and 36 matched controls completed baseline testing: isometric hip strength, lower limb reactive strength, and HAGOS. After rehabilitation, athletes with AGP were retested, and HAGOS was collected at 3 and 6 months after RTP. Results: In total, 36 athletes with AGP completed the program with an RTP time of 9.8 ± 3.0 weeks (mean ± SD). At baseline, these athletes had significantly lower isometric hip strength (abduction, adduction, flexion, extension, external rotation: d = –0.67 to −1.20), single-leg reactive strength (d = −0.73), and HAGOS (r = −0.74 to −0.89) as compared with the CON cohort. Hip strength (d = −0.83 to −1.15) and reactive strength (d = −0.30) improved with rehabilitation and were no longer significantly different between groups at RTP. HAGOS improvements were maintained or improved in athletes with AGP up to 6 months after RTP, although some subscales remained significantly lower than the CON group (r = −0.35 to −0.51). Two linear regression features (hip abduction and external rotation) explained 11% of the variance in the HAGOS Sports and Recreation subscale. Conclusion: Athletes with AGP demonstrated isometric hip strength and reactive strength deficits that resolved after an intersegmental control rehabilitation program; however, improved hip strength explained only 11% of improvement in the Sports and Recreation subscale. HAGOS improvements after pain-free RTP were maintained at 6 months.

Intra-class correlation coefficient (ICC 2,1) ranged from 0.67 to 0.98, the standard error of measurement (SEM) ranged from 2.1 to 5.1% and the minimal detectable change from 8.6% to 17.8%.

Double-leg and single-leg drop jump protocol
Athletes stepped off a 30cm (DLDJ) or 20cm (SLDJ) box and were instructed to keep hands on hips, spend minimal time on the ground and jump vertically as high as possible. Three practice and three maximum effort trials were performed. Jumps were separated by a 30second rest period and two-minute rest between DLDJs and SLDJs. DLDJs were performed first followed by SLDJs on the non-symptomatic (AGP) or dominant (CON) side.

Intersegment control rehabilitation program
The rehabilitation program was designed to address trunk, pelvis and lower limb intersegmental control through strengthening, linear running and change-of-direction mechanics (King et al., 2018). Intersegmental control describes the relationship between the trunk, pelvis, hip, knee and ankle during dynamic movements and a loss of control has been suggested to play a role in the propagation of athletic groin pain. (Franklyn-Miller et al., 2017).
The intersegmental control rehabilitation program consists of three levels, with each level designed to address specific components of recovery. Level 1 focuses on intersegmental control through strengthening exercises, level 2 focuses on intersegmental control through linear running technique and progression of running load tolerance, and level 3 focuses on intersegmental control through change-of-direction technique and progression back to high speed running. Progression from level 1 to level 2 is achieved with a pain-free cross-over test (in the modified Thomas test position), progression from level 2 to 3 occurs with pain-free squeeze test (in 45° hip flexion), pain-free completion of linear 'Run A' program and symmetrical hip range-of-motion (flexion 90° internal rotation mobility). Finally, progression from level 3 to return-to-play is achieved with pain-free completion of 'Run B' program and multi-directional drills. Table 1 outlines the exercise streams for each level of the program and Table 2 outlines the exercise progressions for each of the exercise streams.
Once athletes are cleared to return-to-play, they are advised to complete one full strength session per week (i.e. level 1 control, strength and power exercises), three sessions of the level 1 intersegmental control exercises (e.g. as part of an athlete's pre-pitch/gym preparation) and are to perform the linear and multi-directional technique drills prior to their sporting activity.

Equipment
The equipment required includes a squat rack, barbell, weights, box/chair (60cm, 45cm), resistance bands and 5kg medicine ball.

Rehabilitation sessions
Rehabilitation sessions were taken by one of three physiotherapists who were trained in the delivery of the intersegmental control rehabilitation program. All physiotherapists had five or more years clinical experience.
Athletes started their rehabilitation on the same day as their initial testing session. Each rehabilitation session was one-to-one and approximately 1 hour in length. Athletes are taken through the various exercises depending on which rehabilitation level they are in (Table 1) with the difficulty of the exercise selected, progressed or regressed depending on the participants ability to execute with appropriate technique (good form and no reproduction of symptoms) ( Table 2). These sessions took place every 14-21 days depending on athlete availability.
In between supervised rehabilitation sessions, athletes were instructed to perform the rehabilitation program at their own training base. Each subject was given a printed handout of all the exercises with the main coaching cues for each), in addition to each exercise being captured on video using Dartfish™ software and the videos hosted online for the athlete to review between sessions. Athletes were instructed to complete a weekly exercise diary to help ensure compliance. Athletes were advised that should any exercise reproduce their symptoms, they should review their videos and amend their technique to resolve and if unable to do so these exercises should be discontinued and their physiotherapist will review during the next rehabilitation session.

Level 1
Level 1 exercises focus on both the control between two segments across one joint (e.g. hip flexor holds) and also multi-segmental movements (e.g. deadlift). For the loaded exercises, the deadlift weight started at approximately 40% bodyweight, front squat 20% bodyweight and split squat bodyweight only. The weight was gradually increased as athletes could reach the appropriate number of repetitions in each set with good control and no symptoms. The importance of correct technique was repeatedly emphasized. Level 1 exercises were included throughout the duration of the rehabilitation program.

Level 2
The focus of the level 2 exercise streams (Table 1) is to improve intersegmental control during linear running with exercise drills designed to address commonly observed technical faults (e.g. poor lumbopelvic control at toe-off, poor swing leg recovery) or reduced neuromuscular capacity (e.g. contralateral hip drop during the stance phase of the running gait). Once athletes complete the linear running drills, they carry out the Run A program (Table 3). This was developed for field-sport athletes to gradually build tolerance to running loads and intensity while assessing the athletes' tolerance and suitability for progression. It starts with low volume and low intensity, both of which increase at different points through the program. Athletes are instructed to progress, or regress based on a traffic-light system.
Green light means no pain during or the following day and athletes can progress to the next running session. Red light means increased pain during or the following day and athletes are instructed to repeat the same session or drop back a session when scheduled until they can tolerate it and then progress to the next session (by obtaining a green light).

Level 3
The focus of the level 3 exercise streams is to improve intersegmental control during multidirectional movements, lateral rate of force development and agility prior to returning to sports (Table 1). Athletes also progress from Run A to Run B program which increases exposure to high speed running. Once athletes complete the multidirectional drills (and linear run drills) they carry out the Run B program. The drills are executed at as high an intensity as possible without reproduction of symptoms.

Weekly frequency
Level 1 of the rehabilitation program is prescribed on a 3-day cycle: day 1 all exercises (control, strength and power), day 2 control exercises only and day 3 rest. Level 2 and 3 is prescribed on a 4-day cycle: day 1 all exercises (control, strength and power), day 2 Run A or B (depending on which level an athlete is at), day 3 control exercises only, day 4 rest.