A Novel Method of Assessing Trunk Lateral-Flexion Range of Movement in First-Class Cricket Players

Ethics approval for this study was granted by 2 university human research ethics committees, and all participants supplied written informed consent.

Ten first-class cricket players from the same English county team (6 fast bowlers, 1 spin bowler, and 3 specialist batsmen [mean age = 26.8 years, mean height = 182.7 cm]) attended 1 testing session. Five of the fast bowlers had previously sustained a side strain injury, including 1 who underwent rib resection 5 years earlier. Recruits were included if they were free of any injury that would affect training or participation in competitive matches at the time of testing. Participants had not bowled in a competitive match on the day of testing, as this might have affected the results. They were excluded if inactive in competitive cricket for any reason.

The barefoot participant stood with his side to a flat wall, feet hip-width apart, with the base of the fifth metatarsal and greater trochanter touching the wall. The arm adjacent to the wall was abducted overhead and the elbow comfortably flexed so that this arm was not pushing the participant away from the wall. The individual was instructed to “slowly run your fingers down the outside of your leg and reach as far as you can while continuing to look straight ahead.” He maintained contact with the wall at both lower limb points and kept both feet and heels flat on the floor at all times. The participant was given specific instructions and tactile feedback to keep the lateral border of the foot in contact with the wall (Figure 2). The physiotherapist stood near the participant's feet to ensure compliance with this instruction. The individual laterally flexed at the trunk without trunk or hip flexion or extension. The measurement was obtained in both directions: toward and away from the bowling arm. Two methods of determining ROM were performed for comparison of reliability: FLR and FIB.

The measurements were conducted by 3 experienced first-class cricket team physiotherapists (13, 6, and 8 years of experience) using a retractable tape measure (Nurses Tape Measure; Medisave). Testing was completed in a single session to prevent potentially confounding of the data due to time-of-day variations and activity between testing sessions. Each physiotherapist tested each participant in a randomized order for both trials to demonstrate intrarater reliability. After every measurement, the physiotherapist ensured that the ROM mark on the participant's leg was completely removed using an alcohol wipe. Each measurement was taken for a separate movement, rather than having multiple testers measure the same movement. This introduces the variable of the actual difference between movements in addition to the reliability of the measurement technique between and within testers.

Participants were recruited from men's professional cricket teams in Australia and England. They were included if they were aged 18 years or older and selected as a fast bowler. A total of 24 teams were invited to take part (each team had approximately 5 fast bowlers), and data were provided by 72 participants in season and 49 participants between seasons. At the start of data collection, each person's age, standing height, bowling arm, and number of previous side strain injuries were recorded. Only data on injury-free bowlers were included.

The physiotherapists for each team recorded the ROM of participants on each occasion. Lateral-flexion ROM measured from the floor was first obtained 3 months before the start of the preseason (month -3) and repeated at intervals not exceeding 1 month until the fourth month of the competitive season (month 4) in year 1. During years 2 and 3, the first measure was taken at the start of preseason (month -3) and repeated at intervals not exceeding 1 month until the first month of the competitive season (month 1). Measurements were taken before any bowling on that day. Measurement points were labeled according to their timing either before or after each bowler's competitive season.

Changes in ROM within the preseason were assessed at 3 time points. The latest measures were taken in the month before the start of each bowler's respective competitive season. The prior measures were taken not more than 1 month apart.

Changes in ROM within the competitive season were assessed at 5 time points. The first measure was taken in the month before the start of each bowler's respective competitive season. The subsequent measures were taken not more than 1 month after each preceding measure.

Changes in ROM between competitive seasons were assessed at 3 time points. Each measure was taken in the first month of each bowler's respective competitive season over successive seasons.

Reliability was calculated on a single-measure basis (SPSS, version 27.0.1.0; IBM Corp) to match the clinical setting, in which ROM was only measured once. Intrarater and interrater reliability was determined using the intraclass correlation (ICC) with 95% CIs, SD, standard error of measurement (SEM), and minimum detectable change (MDC) in both directions. Reliability was reported as poor (> 0.5), moderate (0.5–0.75), good (0.75–0.9), or excellent (> 0.9) based on published criteria.²⁷  The SEM indicates the amount of variability in a test due to measurement error, whereas MDC is the smallest amount of change that represents real change beyond measurement error. Statistics were calculated for both FIB and FLR. Absolute agreement was chosen over consistency.

Intrarater and interrater reliability was calculated for all 3 testers using a 2-way random-effects model looking for absolute agreement based on a single (first) measure of each tester.

The SEM provides an absolute index of reliability, in the same units as the measurement, thereby quantifying the precision of the test scores. We determined the SEM from the square root of the mean square error value generated from a 1-way repeated-measures analysis of variance.²⁸  The MDC was calculated using the formula MDC = SEM × 1.96 × √2.

Range of motion was identified using FLR due to ease of measurement. A lower number represents a larger magnitude of motion. Ranges presented are minimum to maximum. Unless stated otherwise, all data were normally distributed for all time points (Shapiro-Wilk significance value >.05). Data were analyzed for seasonal variation using a 1-way repeated-measures analysis of variance. Given the asymmetric demands of the bowling action and potentially different effects of past side strain injury on the behavior of ROM in either direction, data for the directions toward and away from the bowling arm were considered independently. Cases with any missing time points were excluded. Unless specified otherwise, sphericity was assumed for all significance values because the Mauchly test values were >.05. Differences in ROM between time points were mapped on a scatterplot to highlight individual variations in LF ROM, with 95% confidence bands based on the SEM for interrater reliability using the FLR.

Intrarater reliability for all raters was good to excellent when LF ROM FLR and FIB were measured both toward and away from the bowling arm (Table 1). The FLR ICCs were marginally higher than the FIB ICCs for all 3 raters. The MDC for the FLR was lower for all 3 raters when measuring LF ROM away from the bowling arm. Much greater MDC variation was present among raters for measures toward than away from the bowling arm.

Interrater reliability demonstrated similar ICCs for the FLR and the FIB, both toward (FLR = 0.91, FIB = 0.84) and away from (FLR = 0.96, FIB = 0.94) the bowling arm. The MDCs for away from the bowling arm were almost identical for the FLR and FIB (FLR away = 28 mm, FIB away = 27 mm, FLR toward = 41 mm, FIB toward = 48 mm).

Data were collected over 3 years from the start of the England County cricket season in 2011 and the Australia State cricket season in 2011–2012. A total of 1736 ROM measurements were taken of 238 first-class cricket fast bowlers by physiotherapists for all 24 first-class teams and each national team from Australia and England. Data received from national teams were distributed to the sets for each bowler's domestic first-class team. Data for bowlers who changed teams between seasons were transferred to the team dataset in which the bowler began the data-collection period.

Complete ROM datasets were obtained from 56 bowlers (24% of cohort, mean age = 24.4 years [range = 18–36 years], mean standing height = 188.7 cm [range = 175–203 cm]) from 9 teams at 3 time points in a single preseason. There were 49 right-arm and 7 left-arm bowlers; data were analyzed as toward and away from the bowling arm to account for this. Twenty-seven bowlers had a history of side strain injury: 22 bowlers had 1 injury, 4 bowlers had 2 injuries, and 1 bowler had 3 injuries. No difference in ROM existed either toward or away from the bowling arm or among the 3 time points, with P values >.05 (Table 2). A total of 84% of measurements toward the bowling arm and 67% of measurements away from the bowling arm varied within the 95% CIs such that an individual's ROM varied due to the systematic error of the measurement (Supplement 1).

Complete data were provided by 72 bowlers (30% of cohort, mean age = 25.1 years [range = 18–39 years], mean height = 187.2 cm [range = 173.6–204 cm]) from 13 teams at 5 time points in a single competitive season. There were 61 right-arm and 11 left-arm bowlers. Thirty-nine bowlers had a history of side strain injury: 30 bowlers had 1 injury, and 9 bowlers had 2 injuries.

No difference in ROM existed away from the bowling arm or among any of the 5 time points, with P values > .05 (Table 3). However, a difference in ROM occurred toward the bowling arm among the 5 time points. Post hoc pairwise comparisons revealed that the active trunk (AT) LF ROM toward the bowling arm was different between months 1 and 4 (P < .01). Yet the mean difference (15.8 mm) was smaller than the MDC for the ROM test. Therefore, the AT LF ROM both toward and away from the bowling arm did not vary more than the measurement error from the final month of preseason and within the competitive season. Seventy-six percent of measurements toward the bowling arm and 62% of measurements away from the bowling arm varied within the 95% CIs such that an individual's ROM varied due to the systematic error of the measurement (Supplement 2).

There were 49 bowlers (21% of cohort, mean age = 25.4 years [range = 18–37 years], mean standing height = 188.5 cm [range = 176.0–204 cm]) from 14 teams with complete datasets for 3 time points being the first measure in 3 consecutive competitive seasons. A total of 42 were right-arm and 7 were left-arm bowlers. A history of side strain injury was present in 31 bowlers: 25 bowlers had 1 injury, 4 bowlers had 2 injuries, 1 bowler had 3 injuries, and 1 bowler had 4 injuries.

No difference in ROM existed, either toward or away from the bowling arm, among the 3 time points, with P values > .05 (Table 4). Sixty-six percent of measurements toward the bowling arm and 51% of measurements away from the bowling arm varied within the 95% CIs such that an individual's ROM varied due to the systematic error of the measurement (Supplement 3). Therefore, LF ROM within the first month of the competitive season did not vary.

In this study, we describe a new simple and reliable method of measuring AT LF ROM. The reliability of previous methods has varied from poor to excellent, with some of those methods requiring expensive and cumbersome equipment.¹  Further, LF ROM in professional cricket players was shown to be consistent during the preseason and competitive season and between seasons. Establishing the reliability and natural variation of LF ROM is a critical step in understanding its role in the clinical assessment, screening, and prognosis of side strain injuries among cricket and throwing athletes.

Lateral-flexion ROM measured with this novel method has been demonstrated to have good to excellent intrarater and interrater reliability. The MDC was smallest for the method to the floor for most measures. Reliability statistics were similar for the direction toward the bowling arm and away. Toward the bowling arm indices of interrater reliability were comparable with those for intrarater reliability. Greater variability existed for the direction away from the bowling arm.

The levels of reliability identified in this study are consistent with those of Ng et al (2001),¹⁷  who used a custom-built pelvic-restraint device. We suggest that our method was similarly reliable with the distinct advantages of simplicity, minimal equipment, and time, as a single measure can be completed within 30 seconds. This is important in the clinical and sporting settings when assessing a patient in pain and screening many players.

Side listing of the pelvis and lumbar spine is a common coupling movement with LF of the trunk and lumbar spine. A tendency to deviate in the sagittal and horizontal planes has previously been reported to reduce the reliability of the LF ROM measurement compared with sagittal movements.²⁹  Standing in close proximity to and facing a wall did not improve reliability.²⁹  The lack of complete pelvic fixation limiting free motion of the pelvis in terms of sagittal rotation was also noted to contribute to the poor reproducibility of computerized measuring equipment.⁹  The participant's desire as well as the instructions to reach to maximize ROM may also encourage hip and spine flexion. The novel method we described overcomes the concern about side listing by insisting that the participant's lateral foot and greater trochanter maintain contact with the wall, thus providing a physical block. The instruction for the participant to maintain a straight-ahead gaze was also considered helpful, which has been observed earlier.²⁹  This necessitates that the participant avoid cervical and, consequently, trunk and hip flexion, optimizing the purity of the LF movement.

Several strengths of the measurement method to the floor exist. First, the measurement is an objective measure of distance that does not require palpation of any bony landmarks. This distance is a direct measure to the floor with no skin movement under a measurement tool. The measure is noninvasive, and the only equipment required in a wall and tape measure. The good to excellent reliability of the test is based on a single measure, making it quick to implement in the clinical context. Another major strength of the measurement method is its simplicity. Two of the 3 testers in this study had no previous experience using the test; they received only a written and pictorial description and a single demonstration before performing the measurements. The method has now been shown to have good to excellent reliability, and its SEM and MDC have been determined and can be factored into research and clinical decisions. These are essential steps for implementation of the test in prospective research and clinical practice.

Range of motion did not vary during measurements 1 month apart within the preseason, within the competitive season, or among 3 competitive seasons. Side strain occurs frequently in the initial months of the season.³⁰  This suggests that the increased demands of transition from training to competition may be a contributing factor.

For the clinician who is managing athletes at risk of sustaining side strain injuries, our work has certain implications. The lack of variation in ROM within the preseason and competitive season and between seasons indicates that a baseline measure taken in the 3 months before the start of the competitive season is consistent not only during the season but also during subsequent seasons.

This study was methodologically robust, with a prospective study design and large dataset. Good to excellent levels of intrarater and interrater reliability existed, the measurements were consistent with how tests are used clinically, and the participants were representative of a clinical population. The findings provide a pragmatic and simple measurement tool that clinicians can use both clinically and in a sporting context.

A limitation of this study was that the AT LF ROM test has not yet been shown to be reliable in injured players, unlike the active knee-extension and passive knee-extension tests for hamstrings injury.³¹  Also, missing data reduced the size of the cohorts for each analysis. However, for this study, we were dependent on the contributions of many physiotherapists working within the time constraints of the first-class cricket season, and measures taken more than 1 calendar month apart or on injured players were excluded.

In summary, with this research, we provide clinicians with a reliable and simple way to evaluate LF ROM in a time-efficient manner. The results may improve clinicians' measurement techniques and reproducibility of LF assessment, which enables its use as a screening tool and an outcome measure after injury. Authors of future studies could investigate the progression of LF ROM during recovery from side strain injury and determine if it is a criterion measure for return to sport.

We demonstrated good to excellent intrarater and interrater reliability of a novel method of measuring LF ROM that is simple and quick to use in the clinical setting. This measurement did not vary during or between preseasons or competitive seasons in a large cohort of uninjured first-class cricket fast bowlers. These findings provide a basis for future prospective researchers to investigate LF ROM as a predictor of injury, clinical assessment test, and predictor of recovery time and recurrence after side strain injury.