The Adductor Squeeze Test and its role in predicting Groin Injury.
Adductor injuries are a common occurrence in field sports, especially sports that involve rapid acceleration and deceleration, reactive change of direction running and kicking. Research shows that groin injuries are ranked as the second, third or fourth most common injury in Gaelic Football, Hurling, Soccer and Australian Rules Football, respectively. The adductor muscles are constantly working during running, acting to stabilize the pelvis during the stance phase and to stabilize the thigh during the swing phase. Given the high running demands of the field sports mentioned above, it is no wonder that adductor injuries are such a common occurrence.
Groin Injuries in Gaelic Football
Extensive research on inter-county Gaelic football players over an 8-year period reported that groin injuries were the second most common injury to occur and accounted for 14.9% of all injuries. This study also reported that the average time lost to a groin injury was 25 days and the likelihood of re-injury was 21.5%, meaning one in every five players who sustain a groin injury, will sustain re-injury to the same muscles. Other researchers have reported that 19% of all Gaelic football injuries occur during a twisting or turning action - actions which have been shown to place increased load on the groin-adductor area. Given the lengthy time lost from sport and the high rate of recurrence, the ability to screen for, and subsequently avoid, adductor injuries should be of upmost importance to a physiotherapist, strength and conditioning coach or sports scientist working with field-sport athletes. So, how can we attempt to do this?
Studies on Gaelic football and Australian rules football players show that adductor strength is reduced in the period proceeding and during the onset of groin pain. Therefore, if we had a reliable and accurate method of measuring adductor strength, we could potentially predict when a groin injury is likely to occur. This method of measuring adductor strength would need to be quick and easy to use, and be proven as a reliable, accurate and valid measurement of assessing adductor strength in field sport athletes, in the literature. Enter the adductor squeeze test!
Adductor Squeeze Test
In 2009, a group of researchers (Malliaras et al., 2009) assessed various methods of measuring hip flexibility and strength and their reliability in predicting future groin injury. These researchers concluded that the adductor squeeze test using a commercially available sphygmomanometer was the only test which reliably discriminated between athletes with groin pain and those without groin pain. Since then, the measurement of adductor squeeze values using a sphygmomanometer has been used in various studies across various cohorts, including rugby, Gaelic football and Australian rules football. In terms of the reliability and validity of the adductor squeeze test, researchers in University College Dublin (Delahunt et al., 2011) performed a study specifically to assess the reliability and validity of the test and found it as an excellent and accurate method of measuring adductor strength. Furthermore, the same researchers then assessed three different testing positions (0°, 45° and 90° of hip flexion) and found the most optimal position for eliciting maximal pressure scores to be 45° of hip flexion (with 90° of knee flexion). Another study then reported the test and testing positions to have excellent inter-rater and intra-rater reliability, which essentially means that an athlete who gets tested by two different testers, will get the same score - which is useful in sporting environments where numerous physiotherapists and strength and conditioning coaches may work with the same team. So from these studies, we now know that the adductor squeeze test is reliable and valid, with excellent inter-rater and intra-rater reliability, and provides maximal scores in the 45° hip-flexion position.
Predicting Groin Injury
Perhaps the most relevant study to date is that from (Delahunt et al., 2016) who linked adductor squeeze test scores below 225 mmHg (measured on the sphygmomanometer) to groin injuries in elite male inter-county Gaelic football players across the course of a season. This study provided preliminary research that adductor squeeze test scores could distinguish Gaelic football players at higher risk of groin injury. Of the 55 elite inter-county players in this year-long study (all members of the same team), 10 of them sustained a groin injury during the season, which accounted for 13% of all injuries sustained. The testing data revealed a significant difference in pre-season adductor squeeze test scores between those players who did sustain a groin injury and those who did not. The injured players scored an average of 210 mmHg on their pre-season adductor squeeze test, whereas those who did not sustain a groin injury throughout the season scored an average of 260 mmHg. This data along with the researchers conclusion that a score below 225 mmHg significantly increases the risk of groin injury, is of great relevance to those working in the fields of physio, strength and conditioning and sports science. By helping us predict the risk of injury, we can then take a proactive individualized approach to injury prevention as opposed to a 'one size fits all' approach. Furthermore, other studies have linked adductor squeeze test scores to training load and markers of recovery - suggesting that the test could be used as a method of predicting athlete recovery and fatigue during periods of high training loads. Perhaps this test provides an acute alternative to the commonly used counter movement jump (CMJ) as a method of measuring athlete readiness to train.
Using a Sphygmomanometer
Now that we know the adductor squeeze test to be a valuable test in our arsenal, how do we perform it? In keeping with the literature, the test is performed with the athlete laying face-up on a plinth or on the floor. The athlete crosses their arms across their chest and keeps their head on the bed/floor for the duration of the testing procedure. The sphygmomanometer is then pre-inflated to 10 mmHg and allowed to settle for 30 seconds before being placed between the athletes knees. The test is typically performed at 0° hip flexion (legs straight), 45° hip flexion (with knees in 90° flexion), or 90° hip flexion (with knees at 90° flexion again). As mentioned previously, research has shown that the 45° hip flexion position elicits maximal scores so it is advised to use this testing position alone, if time is a limiting factor. Once the athlete is in the desired testing position, the cuff of the sphygmomanometer is placed between their knees and they are instructed to squeeze the cuff as hard as possible between their knees, for 3-5 seconds. The pressure score will appear on the pressure dial for the tester to see. The maximum value reached is recorded. After each maximal squeeze, the athlete is given a rest period of 15-45 seconds and the process is repeated. A total of three tests is taken in each testing position (0°, 45° and 90° hip flexion) with a two-minute rest period between each test position. The average value in each position is used as the athletes score. This protocol outlined is the most supported and most common in the literature and has been shown to produce accurate, reliable test scores. From a practical perspective, the test should take no longer than 8 minutes, with the athlete resting during the majority of that time.
Although the study by (Delahunt et al., 2016) reported athletes scoring below 225 mmHg to be at a higher risk of groin injury, it has to be taken into account that this data represents elite Gaelic football players. Whilst this data can too be used with athletes of similar field-sports, it is probably more accurate to base your results off data obtained on athletes playing the same sport at the same level. Thankfully, studies have been performed to obtain normative data on both elite senior rugby players and elite underage rugby players, so any exercise professional working within rugby has some reliable normative data to compare their tests to.