Reliability of two new single leg hamstring bridge tests and comparison to isokinetic strength tests

Abstract

BACKGROUND:

Test selection during the return to sport evaluation is an important aspect of ensuring athletes are safe to return to competition.

OBJECTIVE:

To assess the test-retest and inter-rater reliability of two new single leg hamstring bridge tests (SLHBT) and the relationships between these new tests and isokinetic strength of the quadriceps and hamstrings.

METHODS:

Thirty healthy college students completed the study. Two testing sessions were held three to seven days apart. Session one, participants performed two SLHBT as well as concentric isokinetic strength tests for the hamstring and quadriceps at 60, 180 and 300^∘/sec. The participants performed only the two SLHBT during the second session. The first SLHBT, participants performed as many repetitions as possible of the SLHBT in 30-sec, while the second test measured how quickly the participants could perform five repetitions. Intraclass Correlation Coefficients (ICC2,1) were used to assess test-retest reliability while ICC(3,1) were used to test inter-rater reliability.

RESULTS:

The test-retest reliability for the SLHBTs was moderate to good, with ICC(2,1) ranging from 0.68 to 0.75, while the inter-rater reliability were excellent with ICC(3,1) all above 0.98. There were significant correlations between the SLHBT and the isokinetic tests, but all correlations were low to moderate.

CONCLUSION:

This study found good to excellent reliability with the new SLHBT and poor to moderate correlations were noted Therefore, SLHBT may not be an alternative to test hamstring test during the RTS evaluation due to the multiple compensatory strategies athletes may have.

Keywords

Return to sport functional assessments movement system

1. Introduction

Return to sport (RTS) assessments have been used widely by physicians, athletic trainers, physical therapists, and other medical professionals to assess whether an athlete is ready to return to his or her sport [1]. RTS assessments are also used to track progress with athletes and gain a better understanding of what limitations are still present that need to be addressed before the athlete can return to sport [1]. Scores on RTS assessments can also be used to predict if the athlete is likely to be re-injured once they return. According to Ardern et al., returning to sport should not be a single decision made at the conclusion of the rehabilitation process but should be continuously evaluated throughout the entire rehab and recovery process [1]. To understand the process of RTS, it is important to define those aspects. RTS can be defined as an athlete being cleared for full sport participation including strength training, practice, and competition without restrictions [2].

In a previous model of RTS, the team physician was the prominent gatekeeper of the RTS decision [1]. There have been considerable advancements in the return to sport model that now involve other health care providers along with the athlete to make the decision on RTS. Since there are so many stakeholders involved in the RTS process, the final decision should involve all stakeholders (physician, athlete, physical therapist, and athletic trainers) [1]. An established criterion for safe RTS is essential to prevent re-injury and achieve maximal performance. A systematic review found that the RTS decision was based on subjective non-specific criteria, when a more clinical approach would include objective and functional tests [3, 4]. Objective tests include assessing lower extremity strength as well as functional movement patterns.

Strength tests, including isokinetic, isometric, and isotonic testing, are often used to assess probability of functional return in athletes who have suffered an injury [5]. According to Anderson et al. and Eitzen et al., quadriceps and hamstring strength is the most important predictor to a successful rehabilitation and functional return following an ACL repair [5, 6]. To get an objective measure of an athlete’s progression in the rehabilitation process, several types of tests can be performed to measure strength levels in the affected limb and can be compared to the non-affected limb [4]. Isokinetic testing is a frequently used mode of strength testing and is commonly used to determine if an athlete is ready to return to sport [4]. However, this type of testing is not without faults given that the machine is expensive and testing is often time-consuming. Isokinetic testing can be and is usually performed at varying degrees of speeds [4].

Testing usually includes assessment and comparison of quadriceps and hamstring strength [4]. When comparing values obtained during the strength assessment using an isokinetic machine, quadriceps strength limb symmetry index (LSI) is commonly used [4]. A LSI showing 90% strength of the non-affected limb is a commonly accepted value when used in conjunction with other types of testing to determine when an athlete is ready to return to sport and strength in ACL operated limbs are usually weaker than the non-operated limbs [4]. However, non-operated limbs are typically weaker than controls [4]. According to Wellsandt et al., LSI can overestimate an athlete’s readiness to return to sport given that it compares the operated limb to the non-operated limb approximately six months after surgery [7]. Results from that study suggest that the estimated preinjury capacity levels (EPIC) of 90% may be superior given that the operated limb strength at the end of the rehab phase is compared to the non-operated limb at initial evaluation [7]. According to this study, several patients who passed the LSI criteria but did not pass the EPIC criteria sustained a secondary ACL injury [7].

Another assessment of the progression of strength is through isotonic testing. Isotonic testing involves moving a specified amount of weight through a specific range of motion (ROM) [8]. In a study performed by Neeter et al., weight was determined based on how fast a participant could move the submaximal weight through the specified ROM [8]. Weight was increased after each repetition and an average of the five repetitions was recorded [8]. Knee flexion was measured with the same protocol on a knee flexion weight machine [8]. Deficits in strength in the quadriceps and/or hamstrings can result in an inability to RTS at the previous level of play, re-injury, and/or knee pain [5]. The results of the isotonic tests can be used in combination with other functional testing measures to determine the likelihood that the athlete will be able to return to their sport at their previous level of play as well as the likelihood they will be re-injured [8].

Isokinetic testing, which is considered the gold standard for testing strength, uses peak moment to measure hamstring strength [9]. The 90/90 single leg hamstring bridge test is a clinical test that may be performed to measure both the strength and endurance of the hamstring musculature. While isokinetic testing may not measure the hamstring muscle group in a position of susceptibility, the 90/90 SLHBT allows the hamstrings to be tested with the hip and knee at more functional angles [9]. The SLHBT is performed with the hip and knee positioned at 90^∘ of flexion and therefore can test the hamstring muscle group in a more functional capacity [9]. Therefore, Freckleton et al. used the SLHBT to assess the relationship between hamstring strength and muscular endurance and risk of hamstring injury in Australian Rules football players [9]. This study concluded that players who have lower scores on the SLHBT have a significantly higher risk of sustaining a hamstring injury [9]. The SLHBT is an economical and functional test that could be used to examine hamstring muscular strength and endurance of athletes to help determine if they are ready for RTS after injury or they are at risk for future injury. Therefore, the purpose of this study is to assess the test-retest and inter-rater reliability of two 90/90 single leg bridge tests and determine the correlation between these tests and hamstring isokinetic strength testing.

2. Methods

2.1 Research design

A cross sectional study was conducted to determine the test-retest and inter-rater reliability of two newSLHBT as well as the correlation with isokinetic strength testing of the quadriceps and hamstring muscle groups.

2.2 Participants

This study included a convenience sample of 30, 15 males and 15 females, healthy college aged students ranging from ages 21–33. Twenty-six of the 30 participants were right leg dominant, and the remaining four participants were left leg dominant. Leg dominance was determined by which foot they would kick a soccer ball with. Exclusion criteria for this study consisted of any lower extremity injury within the past four months which limited activity for more than three days. All participants provided written and verbal consent, as approved by the University of South Alabama, Institutional Review Board, #17-366 before they were allowed to start the study.

2.3 Testing procedures

Participants performed two 90/90 single leg bridge tests as well as an isokinetic test for hamstring and quadriceps strength. Each participant’s dominant leg was identified through subjective questioning. Balance testing was used with half the participants starting with their dominant leg and half the participants testing the non-dominant leg first. The participants performed a 5-minute warm-up of walking/jogging at a self-selected speed and were allowed 2–3 practice trails of each test before testing started.

The protocol for the 90/90 single leg bridge tests was similar to the protocol in Freckleton et al. [9]. The participant was instructed to lie down on a mat with one heel on the box and the bottom in contact with the mat. The box for initial testing was 43-cm high and the retest box was 46 cm high. Different boxes were used due to testing in two different labs to limit travel for the participants. The test leg was positioned in 90^∘ of hip and knee flexion with the arms crossed across the chest. The non-test leg was held upright in a stationary position to avoid momentum being created and used. A repetition was performed by performing full hip extension and then returning to the starting position. For the first test, the participant was instructed to perform as many repetitions as possible in 30-sec after the “ready, go” signal. Repetitions were not counted if the bottom did not encounter the mat. For the second test, the participant was instructed to perform seven repetitions as fast as possible. The testers recorded the time it took the participant to perform five repetitions. Time started on the participant’s first movement and stopped when the bottom contacted the mat after the fifth repetition. Two trials of both tests were performed with the highest number of repetitions and quickest time being used and there was a one-minute rest between trials. Three testers, all second-year physical therapy students, scored both tests. To measure reliability, participants were retested using the same protocols within 3–7 days after initial testing.

The isokinetic test protocol used was similar to other studies [10, 11]. Participants were set up in the dynamometer (Biodex Medical Systems, Shirley, NY) according to the protocol in the operating manual [12]. Participants performed three separate tests at varying speeds on each leg with a two-minute rest between tests. They performed five repetitions at 90^∘ per second, 10 repetitions at 180^∘ per second, and 15 repetitions at 300^∘ per second. Variables used in the correlations included peak moment/body weight and average power for both knee flexion and extension at all three speeds. Participant had a one-minute rest between tests.

Figure 1.

Single limb 90/90 hamstring bridge test A. starting and finishing position B. middle position, end of movement.

2.4 Statistical analyses

For data analysis, the SPSS software package, Version 25 (IBM inc., Armonk, NY) was used. Interclass Correlation Coefficient (ICC) was used to determine the test-retest, ICC(2,1), and inter-rater reliability, ICC (3,1) for the SLHBT. Streiner and Norman’s scoring of reliability was used where ICC greater than 0.75 is excellent, 0.40 to 0.75 is fair to good, and less than 0.40 is poor [13]. To compare the SLHBT to the isokinetic tests, data from Tester 1 was used and Pearson Correlation Coefficient was used where r below 0.50 was poor, 0.50 to 0.75 was good and above 0.75 was excellent [14]. To determine significance of all analyses, a $p$ value of $<$ 0.05 was set.

3. Results

Table 1
Descriptive statistics (mean and SD): Single leg hamstring bridge tests

	Rater 1		Rater 2		Rater 3
	Day 1	Day 2	Day 1	Day 2	Day 1	Day 2
D 30 sec (reps)	27.8 $\pm$ 6.09	31.3 $\pm$ 7.44	27.9 $\pm$ 5.98	31.2 $\pm$ 7.23	28.1 $\pm$ 6.04	31.8 $\pm$ 7.31
ND 30 sec (reps)	27.2 $\pm$ 5.78	31.2 $\pm$ 6.85	27.4 $\pm$ 5.65	31.4 $\pm$ 6.88	27.5 $\pm$ 5.92	31.8 $\pm$ 6.86
D 5 rep (s)	3.88 $\pm$ 0.87	3.49 $\pm$ 0.67	3.90 $\pm$ 0.83	3.91 $\pm$ 0.70	3.83 $\pm$ 0.84	3.45 $\pm$ 0.65
ND 5 rep (s)	3.91 $\pm$ 0.86	3.51 $\pm$ 0.81	3.51 $\pm$ 0.86	3.52 $\pm$ 0.86	3.89 $\pm$ 0.88	3.50 $\pm$ 0.78

Notes: D: Dominant leg; ND: Non-dominant leg.

Table 2

Descriptive statistics: Isokinetic tests for males and females

	Dominant			Non-dominant
	60^∘/s	180^∘/s	300^∘/s	60^∘/s	180^∘/s	300^∘/s
MALES
Extension peak moment/BW (%)	92.9 $\pm$ 18.0	62.7 $\pm$ 11.3	49.2 $\pm$ 7.52	91.3 $\pm$ 19.5	65.0 $\pm$ 13.4	49.2 $\pm$ 10.1
Extension average power (W)	152 $\pm$ 29.7	271 $\pm$ 45.4	277 $\pm$ 38.7	154 $\pm$ 36.2	279 $\pm$ 55.2	280 $\pm$ 55.8
Flexion peak moment/BW (%)	44.7 $\pm$ 8.21	32.9 $\pm$ 4.89	30.2 $\pm$ 6.02	44.3 $\pm$ 9.61	33.4 $\pm$ 6.49	33.6 $\pm$ 5.23
Flexion average power (W)	85.3 $\pm$ 15.5	137 $\pm$ 38.6	123 $\pm$ 30.8	82.3 $\pm$ 21.3	135 $\pm$ 36.5	120 $\pm$ 34.3
FEMALES
Extension peak moment/BW (%)	84.9 $\pm$ 54.7	48.4 $\pm$ 9.68	36.2 $\pm$ 8.34	67.4 $\pm$ 16.3	50.1 $\pm$ 17.6	36.2 $\pm$ 7.23
Extension average power (W)	89.1 $\pm$ 23.6	160 $\pm$ 44.3	158.2 $\pm$ 49.5	85.7 $\pm$ 27.1	154 $\pm$ 45.0	153 $\pm$ 41.4
Flexion peak moment/BW (%)	35.4 $\pm$ 6.11	26.8 $\pm$ 4.21	27.3 $\pm$ 5.01	33.8 $\pm$ 5.60	26.1 $\pm$ 4.25	26.7 $\pm$ 4.46
Flexion average power (W)	49.1 $\pm$ 15.7	80.6 $\pm$ 28.3	76.6 $\pm$ 31.3	48.3 $\pm$ 12.2	82.1 $\pm$ 23.4	96.0 $\pm$ 69.4

Note: BW: body weight.

Table 3

Test-retest reliability (ICC)

	Rater 1	Rater 2	Rater 3
Dominant 30 sec	0.74	0.73	0.75
Non-Dominant 30 sec	0.73	0.70	0.69
Dominant 5 rep	0.70	0.75	0.68
Non-Dominant 5 rep	0.70	0.74	0.68

Descriptive statistics for the SLHBT and the isokinetic tests are listed in Tables 1 and 2. Shapiro-Wilk tests found all SLHBT tests for all raters and the isokinetic tests did not significantly differ from normality based on an alpha of 0.05. The test-retest reliability for all SLHBT ranged from good to excellent, ICC $=$ 0.68 to 0.75 (Table 3). The non-dominant five repetition test provided the lowest test-retest reliability ranging from ICC $=$ 0.68 to ICC $=$ 0.74, while the dominant 30 second test had the highest test-retest reliability with a range of ICC $=$ 0.73 to 0.75. The inter-rater reliability was excellent and ranged from 0.98 to 0.99 for all tests (Table 4).

Table 4

Inter-rater reliability (ICC)

	Day 1	Day 2
Dominant 30 sec	0.99	0.99
Non-Dominant 30 sec	0.99	0.99
Dominant 5 rep	0.99	0.98
Non-Dominant 5 rep	0.98	0.99

Note: sec: seconds, rep: repetitions.

Table 5

Correlations between 90/90 tests and isokinetic tests (r) for males

	Dominant				Non-dominant
	Ext Tor	Ext Pow	Flex Tor	Flex Pow	Ext Tor	Ext Pow	Flex Tor	Flex Pow
60^∘/s isokinetic tests
30 sec	0.47	0.43	0.27	0.42	0.46	0.54	0.37	0.41
5 rep	0.46	0.46	0.27	0.45	0.45	0.51	0.36	0.38
180^∘/s isokinetic tests
30 sec	0.31	0.36	0.63	0.52	0.20	0.26	0.31	0.37
5 rep	0.27	0.36	0.63	0.57	0.21	0.26	0.29	0.35
300^∘/s isokinetic tests
30 sec	0.00	$-$ 0.09	$-$ 0.03	0.36	$-$ 0.09	$-$ 0.03	0.17	0.33
5 rep	$-$ 0.04	$-$ 0.08	0.02	0.41	$-$ 0.08	$-$ 0.04	0.16	0.31

NOTE: Bold: Significant correlations at $p<$ 0.05; Ext: Extension; Flex: Flexion; Tor: Extension Peak Torque/Body Weight; Pow: Peak Power.

Table 6

Correlations between 90/90 tests and isokinetic tests (r) for females

	Dominant				Non-dominant
	Ext Tor	Ext Pow	Flex Tor	Flex Pow	Ext Tor	Ext Pow	Flex Tor	Flex Pow
60^∘/s isokinetic tests
30 sec	0.14	0.03	0.44	0.34	$-$ 0.15	$-$ 0.17	0.20	0.06
5 rep	0.13	0.03	0.43	0.32	$-$ 0.11	$-$ 0.14	0.20	0.07
180^∘/s isokinetic tests
30 sec	0.47	0.15	0.40	0.43	$-$ 0.02	$-$ 0.13	0.18	0.09
5 rep	0.46	0.15	0.40	0.40	0.02	$-$ 0.10	0.18	0.10
300^∘/s isokinetic tests
30 sec	0.39	0.23	0.21	0.43	$-$ 0.08	$-$ 0.11	$-$ 0.17	$-$ 0.04
5 rep	0.39	0.21	0.18	0.40	$-$ 0.04	$-$ 0.18	$-$ 0.18	$-$ 0.07

NOTE: Ext: Extension; Flex: Flexion; Tor: Extension Peak Torque/Body Weight; Pow: Peak Power.

Table 5 shows the correlations between the SLHBT and isokinetic tests for males while Table 6 list the correlation for females. Results for males found were five significant and good correlations found between the SLHBT and the isokinetic tests. Significant correlations were found between the dominant leg extension peak moment/body weight at 180^∘ sec and the dominant 5-rep and 30-sec test, both $r=$ 0.63; dominant leg flexion peak power at 180^∘ sec and the dominant 5-rep, $r=$ 0.57, and 30-sec test, $r=$ 0.52; and non-dominant leg extension peak power at 60^∘ sec and the non-dominant 30-sec test, $r=$ 0.54. There were no significance correlations found for females.

4. Discussion

The gold standard RTS strength assessment is isokinetic testing; however, it is very expensive and time consuming. The purpose of this study was to assess the test-retest and inter-rater reliability of two new SLHBT and determine the correlation between these tests and isokinetic strength testing. With limited research conducted on the SLHBT, this study provides a valuable clinical tool and another reliable test which may help determine a successful RTS for an athlete with a lower extremity injury. Good test-retest reliability and excellent interrater reliability for both SLHBT. Unfortunately, although there were significant correlations between the SLHBT and the isokinetic tests, all correlations were poor and the significant correlations were between the knee extension variables and the SLHBT.

Test-retest reliability was good with an ICC(2,1) ranging from 0.679 to 0.747. As mentioned before, the non-dominant 5-repetition test had the lowest ICC(2,1) of 0.679, while the dominant 30 second test had the highest ICC(2,1) of 0.747. These results are comparable to results obtained by Freckleton et al. who reported an ICC of 0.77 to 0.89 with their hamstring protocol [9]. Although our results are similar, differences in protocols could be the reason why our ICC is slightly lower. For instance, they used a box height of 60 cm whereas we used a box height of 43 cm for testing on Day One and a box height of 46 cm for testing on Day Two. Also, Freckleton et al. performed the test with the knee at 20^∘ of flexion while our protocol was performed with the knee at 90^∘ of flexion [9]. Participants were also instructed to perform as many repetitions as possible until failure in the study by Freckleton et al.; however, there was a time component in our protocol [9]. Although there are differences between protocols, results between studies are similar with a good ICC for this study. There are other reasons why there may have been some variability in the test scores from Day 1 to Day 2. Participants could have exhibited a learning aspect to the protocol, since the average scores on the second day were better compared to the first day. Day to day performance differences is not unexpected and may be due to several different factors including but not limited to differences in energy/fatigue level due to prior day’s activity or lack/poor sleep and nutrition and a change in motivation. Despite these differences in scores between testing days, the tests demonstrated good reliability and can be performed confidently even if some variation occurs.

Interrater reliability for the two new SLHBT was excellent with an ICC ranging from 0.978 to 0.996. As previously mentioned, the non-dominant five repetition test proved to have the lowest ICC with a range of 0.978 to 0.987. The dominant 30 second test had the highest inter-rater reliability with a range from 0.992 to 0.996. These findings were also similar to those obtained by Freckleton et al. who reported an ICC of 0.89 to 0.91. When compared to test-retest reliability, interrater reliability was better due to using data from the same tests performed on the same day without change in equipment.

Most of the correlations between the SLHBT and the isokinetic tests were poor and non-significant, 94.8%, but there were five significant and good correlations found, all in the male results. Furthermore, correlations between the 5 rep and the 30-sec SLHBTs and the isokinetic tests were very similar since the correlation between the two SLHBTs were excellent, $r=$ 0.98 for both male and female data. Four of the five good and significant correlations were found between the dominant knee flexion isokinetic tests at 180^∘/second the SLBST, while the other good and significant correlation was between non-dominant knee extension peak power and the 30-rep SLBST.

The SLHBTs were created to test the hamstring musculature in a more functional position. These findings suggest that the SLHBT may not measure hamstring muscle performance, and this may be due to the participants using other movement strategies to perform the SLHBT. Furthermore, the findings suggest the SLHBT does not isolate the hamstring muscles, as the isokinetic test does and therefore should not be an alternative assessment during the return to sport assessment. Although the lack of correlation between the SLHBT and the isokinetic test, the SLHBT may have some value in predicting initial injury or re-injury but more research is needed.

This study is not without limitations. One of the biggest limitations is the difference in the box height used on Day One compared to Day Two. A box height of 43-cm was used on Day One due to its location near the isokinetic machine, which was in another building. Since the isokinetic machine was not needed for day two retesting, a box height of 46-cm was used to limit travel for participants. This can be remedied by using the same box height for both testing days. There was also a different number of days between testing for each participant, with a minimum of three days and a maximum of seven days. This could result in some participants having a longer time to recover from testing on day one before retesting on day two, allowing them to perform better. To remove the variance in number of rest days between participants, every participant could be assigned the same number of rest days prior to the beginning of the study. The motivation of each participant may also be different. Some participants valued quality of movement over quantity, while others valued quantity over quality. It was observed that some participants also used different strategies to perform the SLHBT, therefore the movement could be standardized more. The isokinetic machine testing was performed right after performance of the 30-sec SLHBT and five repetition SLHBT. Therefore, fatigue could also play a role in the results that were obtained. Isokinetic testing and both SLHBT could be performed on different days to reduce the effect of fatigue. Lastly, testing was performed on healthy, college-aged students. To gain a better understanding of how this test can best be used as an RTS assessment, testing should be done on participants with knee and/or hamstring injuries.

Future research is recommended on the use of the two new SLHBT for return to play. These studies can focus specifically on participants with lower extremity injuries to detect any discrepancies between the injured and uninjured limbs. Also, normative values for different populations should also be gathered. This will allow the values of participants with lower extremity injuries to be compared to normative values, possibly to help identify individuals at risk for athletic injuries. It is also recommended that an electromyography analysis be performed of the two new SLHBT to determine which lower extremity muscles are activating during the tests. Future studies in each of the above mentioned will allow further verification of the SLHBT as a return to play assessment for individuals with a lower extremity injury.

5. Conclusion

Results indicate the SLHBT are reliable but had had poor correlations between the SLHBT and the isokinetic tests with the strongest correlations between the SLHBT and quadriceps muscle performance. Since the SLHBT are functional tests which assess lower extremity muscle performance, future studies should focus on the effectiveness of using the SLHBT to identify re-injury risk with individuals returning from lower extremity injuries as part of the RTS assessment.

Author contributions

Andy Waldhelm

Conception: Played a vital role in the conception and overall purpose of the project.

Performance of work: Set up project, Collected data.

Interpretation or analysis of data: Main analysis of data.

Preparation of manuscript: Played a vital role in the preparation of the manuscript.

Revision for important intellectual content: Main author who suggest revisions and revised the content.

Supervision: Supervised student with data collection and overall project.

Lauren McElroy

Conception: Played a vital role in the conception and overall purpose of the project.

Performance of work: Assisted with Collected data.

Interpretation or analysis of data: Assisted with interpretation of data.

Preparation of manuscript: Played a vital role in the preparation of the manuscript.

Revision for important intellectual content: Helped revised the content.

Supervision: None.

Cameron Buescher

Conception: Played a vital role in the conception and overall purpose of the project.

Performance of work: Assisted with Collected data.

Interpretation or analysis of data: Assisted with interpretation of data.

Preparation of manuscript: Played a vital role in the preparation of the manuscript.

Revision for important intellectual content: Helped revised the content following initial draft.

Supervision: None.

Haley Barnett

Conception: Played a vital role in the conception and overall purpose of the project.

Performance of work: Assisted with Collected data.

Interpretation or analysis of data: Assisted with interpretation of data.

Preparation of manuscript: Played a vital role in the preparation of the manuscript.

Revision for important intellectual content: Helped revised the content for submission.

Supervision: None.

Jessica Cunningham

Conception: Played a vital role in the conception and overall purpose of the project.

Performance of work: Assisted with Collected data.

Interpretation or analysis of data: Assisted with interpretation of data.

Preparation of manuscript: Played a vital role in the preparation of the manuscript.

Revision for important intellectual content: Helped revised the content.

Supervision: None.

Jared Richards

Conception: Played a vital role in the conception and overall purpose of the project.

Performance of work: Assisted with Collected data.

Interpretation or analysis of data: Assisted with interpretation of data.

Preparation of manuscript: Played a vital role in the preparation of the manuscript.

Revision for important intellectual content: Helped revised the content.

Supervision: None.

Neal Schwarz

Conception: Played a vital role in the conception of the project.

Performance of work: Assisted with developing methods and set up for data collection.

Interpretation or analysis of data: None.

Preparation of manuscript: Played a vital role in the preparation of the manuscript.

Revision for important intellectual content: Helped revised the content.

Supervision: None.

Ethical approval

This study was approved by the IRB from the University of South Alabama, #17-366.

Funding

The authors report no funding.

Footnotes

Acknowledgments

The authors have no acknowledgements.

Conflict of interest

The authors have no conflicts of interest to report.

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Reliability of two new single leg hamstring bridge tests and comparison to isokinetic strength tests

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSION:

Keywords

1. Introduction

2. Methods

2.1 Research design

2.2 Participants

2.3 Testing procedures

3. Results

Table 1 Descriptive statistics (mean and SD): Single leg hamstring bridge tests

5. Conclusion

Author contributions

Ethical approval

Funding

Footnotes

Acknowledgments

Conflict of interest

References

Table 1
Descriptive statistics (mean and SD): Single leg hamstring bridge tests