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Abstract

BACKGROUND:

Both isokinetic testing and functional tests are commonly used during the rehabilitation programme of individuals. Limited information exists in the literature, regarding the correlation between these two testing methods.

OBJECTIVE:

To determine the relationship among quadriceps and hamstrings isokinetic performance values and those derived from three functional assessment tests in a group of healthy participants.

METHODS:

Twenty-five men, were assessed via 1) three functional tests: single hop for distance (SHD), triple hop for distance (THD) and single timed hop (STH) and 2) isokinetic concentric bilateral knee flexion and extension strength values [Mean Peak Moment (MPM), Total Work (TW) and Average Power (AP)] at 60, 180 and 300 ${}^{\circ}$ /s.

RESULTS:

Fair correlations were calculated between the bodyweight normalized scores of the functional tests and those of the normalized isokinetic variables. None of the three angular velocities and none of the three functional tests appeared to be more indicative to functional performance than the others.

CONCLUSION:

There is the need for dynamometry in conjunction with functional tests for a more comprehensive evaluation of knee extension and also flexion performance.

Keywords

Hop tests isokinetics muscular performance functional testing

1. Introduction

It is important for health practitioners to be able to identify patients’ ability to cope with the physical demands placed upon them [1]. According to Barber et al. [2] in order to evaluate functional limitations of the knee joint, an objective measurement simulating sporting activity is required.

Functional performance tests, such as the hop tests, are closed chain activities in nature and therefore assimilate the joint loading forces and kinematics that functionally occur [3]. Hop testing has been proposed as a practical, outcome measure that reflects the integrated effect of neuromuscular control, muscular strength and confidence in the limb requiring minimal equipment and time [4, 5, 6]. Functional activities require not only muscle tension production but also appropriate motor synergies and postural adjustments. Hop tests are the most common used type of closed kinetic chain [CKC] functional tests in the clinical setting due to the use of the contralateral leg [e.g., uninjured] as control for comparisons between limbs [6] and as a reference point for assessing the progress of the rehabilitation program and the return to a competitive functional level [2, 3, 7, 8, 9, 10]. They incorporate a variety of motion principles [i.e., change direction, speed, acceleration, deceleration] imitating dynamic knee stability requirements during sports or simple activities [10, 11, 12]. Functional performance tests are cost effective, they exhibit a high correlation with functional performance [5, 8] and they have become useful in the clinical decision making process [6]. The most frequently used hop tests for the knee joint include the single hop for distance (SHD), triple hop for distance (THD), and single timed hop [STH] test. High reliability for hop tests has been reported in healthy subjects [13, 14].

An alternative strength evaluation test in the clinical setting is the lower limb isokinetic evaluation [15]. Isokinetic dynamometry has become a standard tool for evaluation of muscular strength due to the benefits of range of motion, control, quantifying resistance, and being safe for the patient [2, 11, 16]. It has long been regarded as the principal method for assessing muscle function and imbalances in clinical, research, and sports environment [17]. Some researchers have established the mechanical reliability of the Biodex [18] and have shown that reciprocal, concentric peak moment measures obtained at 60 and 180 ${}^{\circ}$ /sec are very consistent from day to day when a standardized protocol is used [19, 20]. Peak moment is the most often studied strength parameter [21]. Most studies yield results on maximum peak moment [peak moment represents the highest moment output generated by an activating muscle] in relation to the functional tests.

However, human movement cannot be represented only by a peak moment measurement. Another para-meter not so extensively studied is total work [22, 23]. Work has been suggested to be a better indicator of dynamic muscle activity than peak moment since it is a measure of force production throughout the whole range of motion as opposed to one point in the range [20]. Manca et al. [24] in their study tried to quantify the extent of variability in strength variations. They found that the extent of asymmetry between the stronger and the weaker limb was differently portrayed by maximal work (significant inter-limb deficit of 20–24%) and by peak moment (non-significant inter-limb deficit of 12–14%). In 2019 Manca et al. [25] examined people with multiple sclerosis and found that when they have a reduced maximal work they may benefit from strength training approaches aimed at increasing gait speed. They concluded that maximal work was a better indicator of the function of a muscle group than peak moment, as moment must be maintained throughout the ROM and over time. In another study Morrissey [26] suggested that total work may be a better indicator for muscle function than peak moment since peak moment may not reflect the ability of the knee joint to emit force throughout the range of motion after injury. Iossifidou and Baltzopoulos concluded that work depended on the range of motion and added information about muscle and joint function throughout an identified range of motion when compared with peak moment [27]. Both work and peak moment have been found to be reliable measures of muscle performance [28].

Another parameter that needs to be considered is power which indicates how quickly a muscle can produce force. Knee power may better reflect the capacity of muscle to manage knee loads than peak moment. For example, the role of knee extensor strength on the incidence of radiographic knee OA is controversial. In the Multicenter Osteoarthritis Study, knee extensor strength did not predict incident radiographic evidence of knee OA 30 months later [29]. There are studies in the healthy-aging literature that have shown muscle power to be a stronger predictor of functional performance than strength [30, 31, 32]. With aging, the knee extensors show ample losses of power [33]. The authors assumed that the mean and overall values were more accurate in estimating the actual muscular performance as opposed to the peak moment values alone which virtually shows only a maximum performance during a repetition and by itself may not adequately reflect the trend of growth in a range of motion. Peak moment (PM), total work (TW) and average power (AP), are relevant measures of muscle performance [25] and they will be useful as an evaluation tool of the knee joint.

At the same time, the isokinetic assessment is more expensive than a simple hop test. Aditionally, some researchers consider it a poor reflection of functional ability [3, 18] since a single joint assessment of individual muscle groups may not adequately address patients’ functional ability, particularly in sports. Open kinetic chain (OKC) training alone cannot adequately prepare the patient to return to a dynamic functional level. Since both methods are valuable for their own merit it would be of clinical value to know the correlation between performance in the functional tests and flexors’ and extensors’ muscle group isokinetic strength test. Although hop tests are reported to test components of strength, power, and balance, to our knowledge the extent to which deficits on a single-leg hop test correlate with any of these factors has not been thoroughly investigated [6]. Understanding these relationships would improve the clinical usefulness in detecting imbalances and deficits in preseason screening and after injury [6].

Some studies have shown a lack of strong correlation between isokinetic and functional measures [34, 35] with some researchers showing fair and moderate to good correlations [22, 23, 34], while others show little or no correlations [3, 36, 37]. These differences may emerge from the variety of the pathological conditions evaluated, since these correlations have been shown in patients with conditions like anterior cruciate ligament reconstruction [23, 38] with patellofemoral pain syndrome [39], knee osteoarthritis [40], total knee replacement [41, 42] etc. Differences in the results may also stem from differences in methodologies, in the selected individual populations evaluated, the test methods, equipment, etc. If the literature is divided between small and large correlations it would be important to have a firm ground for a clinical decision making in order to facilitate the use of the hop tests as a standardized performance based outcome measure. Specifi-cally, further information regarding not only the peak moment but also average power and total work is necessary to accurately plan rehabilitation programmes and to more confidently make clinical decisions about individual patients.

Isokinetic testing supplemented by the hop tests can create a better approach to the patient’s assesment. Moreover, in the lack of an isokinetic device, a strong correlation between the two would suggest that hop tests can provide the clinician with an important hindsight of the condition of the patient.

The aim of the urrent study was therefore to explore the correlations among isokinetic knee flexors and extensors strength-related variables normalized to bodyweight (BW): mean peak moment to body weight – MPM/BW; total work to body weight – TW/BW; average power to body weight - AP/BW and three functional hop tests.

2. Methods

2.1 Subjects

Twenty-five individuals, 25 men [mean age $=$ 23.68 $\pm$ 3.8 years; mean height $=$ 175.4 $\pm$ 7.7 cm; mean mass $=$ 73.44 $\pm$ 11.83 kg) participated in this study (Table 1). Subjects’ history were free of any hip, knee, ankle, or back injuries that required treatment by a physician. The study protocol carried out in accordance with the Code of Ethics of the World Medical Association (Declaration of Helsinki) and approved by the Ethics Committee of the Technological Educational Institute of Central Greece [School of Health Sciences 118/02-10-2018). A signed informed consent was obtained from all participants before their enrolment in the study as well as the rights of subjects were protected.

Table 1
Anthropometric data and the descriptive statistics [mean, standard deviation, range] for the 25 participants

	Discriptive statistics
Characteristics [ $N=$ 25]	Range	Min	Max	Mean	SD
Body weight [kg]	47.9	52.2	100.1	73.44	11.83
Body height [cm]	26	162	188	175.44	7.77
Age [years]	12	18	30	23.68	3.80

2.2 Functional assessment

Subjects were allowed a 5 minutes warm-up session on a Monark stationary bicycle and self-stretching of the quadriceps, hamstrings, gastrocnemius and soleus muscles. Measures of functional performance included three hop tests: the single hop for distance [SHD), the triple hop for distance (THD) and the single timed hop test (STH, 2, 8, 14, 43). The first extremity tested was randomly selected. Each functional test was performed two times by each leg. Subjects were asked to perform with maximal effort and therefore use of arm swing was not discouraged [44].

Table 2
Descriptive statistics [mean, standard deviation, range] for all functional data in dominant limbs

	Discriptive statistics
Characteristics [ $N=$ 25]	Range	Min	Max	Mean	SD
SHD/BW	278.320	123.709	402.029	207.233	57.375
THD/ $\Sigma$ B	570.050	489.810	1059.860	708.015	135.156
STH/ $\Sigma$ B	2.868	1.548	4.416	2.750	0.713

Min: Minimum, Max: Maximum; SD: Standard deviation; SHD: Single Hop for Distance; THD: Triple Hop for Distance ; STH: Single Timed Hop.

The SHD was performed to determine the distance hopped in a single hop on one leg. The participant was standing on the dominant limb, was hopping as far as possible, and was landing on the same limb [2, 14]. The subject was required to land on one leg. Failure to land on the supporting limb resulted in a rehop [34]. The THD measured the total distance hopped on the dominant limb in three consecutive straight hops [14]. The STH test assesses the time required to cover a distance of 6 m using large forceful one-legged hopping motions. The investigator was standing at the finish line with a standard stopwatch. Time was recorded to the nearest 1/100s [2, 14, 43].

2.3 Isokinetic assessment

Isokinetic assessment was conducted in the Human Performance and Rehabilitation Laboratory of the University on a Biodex System 3 pro (Biodex Systems, Inc, Corporation, Shirley, NY, USA) isokinetic dynamometer. Subjects performed concentric contractions at 60, 180 and 300 ${}^{\circ}$ /s. Knee flexors and extensors were selected for analysis because of their significant contribution to functional activities. Contractions were performed through a range of motion from 0 ${}^{\circ}$ to 90 ${}^{\circ}$ of knee flexion (full extension defined as 0 ${}^{\circ}$ ), and all limbs were gravity compensated. Testing order progressed from the slowest to the highest speeds. Subjects completed five maximal repetitions at 60 ${}^{\circ}$ /s, followed by a 60-second recovery, then completed ten maximal repetitions at 180 ${}^{\circ}$ /s and 30 maximal repetitions at 300 ${}^{\circ}$ /s. To ensure maximal effort, standardized verbal encouragement was provided to all subjects.

Table 3
Descriptive statistics of normalized to BW isokinetic parameters of PM, TW and AP at 60 ${}^{\circ}$ /s, 180 ${}^{\circ}$ /s and 300 ${}^{\circ}$ /s in dominant limbs

	60 ${}^{\circ}$ /s		180 ${}^{\circ}$ /s		300 ${}^{\circ}$ /s
	EXT	FLEX	EXT	FLEX	EXT	FLEX
MPM/BW [%]
Range	2.022	1.165	1.890	9.635	0.997	19.647
Min	1.890	0.726	1.633	9.084	1.116	19.195
Max	3.912	1.891	3.523	18.719	2.113	38.842
Mean	2.815	1.195	2.038	13.841	1.539	30.306
SD	0.434	0.245	0.382	2.415	0.268	4.808
TW/BW [%]
Range	9.635	6.938	14.615	12.887	19.647	16.410
Min	9.084	5.548	8.965	4.197	19.195	9.684
Max	18.719	12.486	23.580	17.085	38.842	26.094
Mean	13.841	8.595	18.972	11.777	30.306	17.159
SD	2.415	1.894	3.015	2.955	4.808	4.465
AP/BW [%]
Range	1.404	11.780	1.424	16.115	1.993	1.290
Min	1.175	0.705	2.677	0.970	1.448	0.668
Max	2.579	12.486	4.101	17.085	3.441	1.958
Mean	1.798	1.575	3.227	2.482	2.394	1.246
SD	0.320	2.298	0.369	3.092	0.437	0.344

Min: Minimum; Max: Maximum; SD: Standard deviation; EXT: Extension; FLEX: Flexion; MPM/BW $=$ mean peak moment to body weight [%]; TW/BW $=$ total work to body weight [%]AP/BW $=$ average power to body weight [%].

2.4 Statistical analysis

The collected data were processed by using the Statistics Package for Social Sciences (SPSS Version 21.0; IBM Corporation, NY, USA). Descriptive statistics (mean, standard deviation, median, minimum and maximum) were computed for all variables derived from the isokinetic tests as well as all the functional testing data. Before the processing of the data, isokinetic test values and also functional testing values were normalized to Body Weigth (BW). Since our sample tested was less than 50 individuals, Shapiro-Wilk test was carried out to assess normality distribution of the variables [45, 46]. Pearson product-moment correlation coefficients medothology for parametric data and the Spearman’s rank-order correlation coefficients for the non-parametric data were carried out to determine the relationship between the three normalized to BW functional performance measures (SHD, THD, STH) and isokinetic parameters of the quadriceps and hamstrings muscle group. The following criteria were used to rank the $r$ values: 0.00 to 0.25 indicated little or no correlation, 0.25 to 0.50 suggested a fair degree of correlation, 0.50 to 0.75 showed a moderate to good relationship, and values over 0.75 indicated a very good to excellent correlation [47]. A $p$ value $<$ 0.05 was considered to be significant in the above statistical tests.

3. Results

The anthropometric data and the descriptive statistics (mean, standard deviation, range) for the 25 participants are presented in Table 1. Table 2 presents the mean, standard deviation and range for all functional data and Table 3 presents descriptive statistics (mean, standard deviation, range) of all isokinetic variables for the dominant limbs. Correlations between normalized to BW functional tests and isokinetic parameters are presented in Table 4. Observing each functional test individually, the results show that with regard to the SHD/BW test, the only correlation found was a positive fair correlation ( $r=$ 0.419, $p=$ 0.037) with extensors’ MPT/BW at 180 ${}^{\circ}$ /s (Table 4).

Table 4
Correlations between normalized to BW functional tests and isokinetic parameters

	MPM/BW [%]						TW/BW [%]						AP/BW [%]
	60 ${}^{\circ}$ /s		180 ${}^{\circ}$ /s		300 ${}^{\circ}$ /s		60 ${}^{\circ}$ /s		180 ${}^{\circ}$ /s		300 ${}^{\circ}$ /s		60 ${}^{\circ}$ /s		180 ${}^{\circ}$ /s		300 ${}^{\circ}$ /s
	$r$	$p$	$r$	$p$	$r$	$p$	$r$	$p$	$r$	$p$	$r$	$p$	$r$	$p$	$r$	$p$	$r$	$p$
Extensors
SHD/BW	0.219	0.292	0.419	0.037	0.229	0.270	0.296	0.151	0.211	0.312	0.073	0.728	0.378	0.062	0.348	0.088	0.035	0.870
THD/BW	0.293	0.155	0.585	0.002	0.405	0.044	0.247	0.234	0.408	0.043	0.411	0.041	0.345	0.092	0.659	0.000	0.403	0.046
STH/BW	$-$ 0.385	0.057	$-$ 0.192	0.357	$-$ 0.179	0.393	$-$ 0.406	0.044	$-$ 0.363	0.074	$-$ 0.179	0.393	$-$ 0.408	0.043	$-$ 0.281	0.174	$-$ 0.233	0.262
Flexors
SHD/BW	$-$ 0.013	0.951	0.145	0.488	0.100	0.634	0.269	0.193	0.206	0.323	0.165	0.432	0.118	0.575	0.212	0.310	0.087	0.679
THD/BW	0.312	0.129	0.472	0.017	0.298	0.147	0.232	0.264	0.432	0.031	0.425	0.034	0.072	0.734	0.528	0.007	0.368	0.070
STH/BW	$-$ 0.432	0.031	$-$ 0.196	0.349	$-$ 0.238	0.252	$-$ 0.377	0.063	$-$ 0.295	0.152	$-$ 0.335	0.101	$-$ 0.436	0.029	$-$ 0.295	0.152	$-$ 0.423	0.035

SHD: Single hop for distance; THD: Triple hop for distance; STH: Single timed hop; BW: Body Weight; IROM: Isokinetic ROM; AP/BW $=$ average power to body weight [%]; MPM/BW $=$ mean peak moment to body weight [%]; TW/BW $=$ total work to body weight [%].

Regarding the THD/BW test, positive moderate to good correlations were found in extensors’ MPM/BW ( $r=$ 0.585, $p=$ 0.002) and AP/BW ( $r=$ 0.659, $p=$ 0.000) at 180 ${}^{\circ}$ /s and in flexors’ AP/BW ( $r=$ 0.528, $p=$ 0.007) at 180 ${}^{\circ}$ /s. Positive fair correlations were found in extensors’ TW/BW ( $r=$ 0.408, $p=$ 0.043) at 180 ${}^{\circ}$ /s and positive fair correlations in extensors’ MPM/BW ( $r=$ 0.405, $p=$ 0.044), in TW/BW ( $r=$ 0.411, $p=$ 0.041), and also in AP/BW ( $r=$ 0.403, $p=$ 0.046) at 300 ${}^{\circ}$ /s. Aditionally, positive fair correlations with flexors’ MPM/BW ( $r=$ 0.472, $p=$ 0.017) at 180 ${}^{\circ}$ /s and TW/BW ( $r=$ 0.425, $p=$ 0.034) at 300 ${}^{\circ}$ /s, were found (Table 4).

In the STH/BW test, negative fair correlations were found with extensors’ TW/BW ( $r=$ $-$ 0.406, $p=$ 0.044) and also AP/BW ( $r=$ $-$ 0.408, $p=$ 0.043) at 60 ${}^{\circ}$ /s. Aditionally, there was negative fair correlations with MPM/BW ( $r=$ $-$ 0.432, $p=$ 0.031) and AP/BW ( $r=$ $-$ 0.436, $p=$ 0.029) at 60 ${}^{\circ}$ /s as well as AP/BW ( $r=$ $-$ 0.423, $p=$ 0.035) at 300 ${}^{\circ}$ /s (Table 4).

4. Discussion

This study investigated whether the use of 3 para-meters of isokinetic evaluation i.e., AP, MPM and TW normalized to body weight, would yield a correlation between functional and isokinetic strength testing. The authors hypothesized that since participants have to control their body weight when performing the functional tests, the three isokinetic variables if they are expressed in terms of BW they will show an even greater correlation with function.

4.1 Single hop distance test

Although many studies investigated the effect of isokinetic muscle strength on the SHD performance, the examination of the correlation of the SHD with isokinetic parameters in the literature, is divided. Anderson et al. [36] measured athletes and Lephart et al. [3] and Sekiya et al. [37] examining anterior cruciate ligament-insufficient athletes, both found low correlations between PT at 60 ${}^{\circ}$ /s and 180 ${}^{\circ}$ /s with vertical jump. Barber et al. [2] found a correlation between isokinetic quadriceps weakness at 60 ${}^{\circ}$ /s and lower hop scores. Pincivero et al. [22] evaluated the relationship between isokinetic flexors and extensors PT at 60 ${}^{\circ}$ /s and 180 ${}^{\circ}$ /s and the SHD test. They found low to moderate correlations between the SHD test and the isokinetic variables for the flexors and the extensors at both angular velocities.

However, when Greenberger and Paterno [34] examined the relationship between the quadriceps at 240 ${}^{\circ}$ /s and SHD, they found a strong correlation for the dominant limb ( $r=$ 0.782). English et al. [35] evaluated 30 healthy subjects, 18–30 years old, isokinetically and functionally. The isokinetic evaluation was performed at 60 ${}^{\circ}$ /s, while functional perfomance was evaluated by the SHD test. They concluded that functional tests such as the SHD can be used to assess the functional performance of the knee muscles.

Our results show that a single hop for distance score incorporating the body weight of the individual does not represent any of the 3 isokinetic strength para-meters examined. A single joint assessment of the knee may not address patients’ functional ability adequately. If some researchers need more data on this particular hop test they will have to evaluate specific pathological conditions.

4.2 Triple hop distance test

For the triple hop distance THD test our results showed moderate to good correlations at 180 ${}^{\circ}$ /s angular velocity with all 3 isokinetic values at both flexors and extensors. At 300 ${}^{\circ}$ /s our results showed fair and moderate to good correlations with all 3 isokinetic values only for the quadriceps muscle. There were no correlations at the slower angular velocity of 60 ${}^{\circ}$ /s. It seems that the higher-velocity quadriceps strength assessment is more in line with the functional demands for rapid strength development of the quadriceps during the THD.

The results of this study support previously cited research which documented a correlation between knee muscle strength [mean peak moment – MPM] and the triple hop for distance test. Selistre et al. [48] examined the relationship between extensor moment with the performance in triple hop distance in professional soccer players and the only statistically significant correlation was at 180 ${}^{\circ}$ /s ( $r=$ 0.43). Hamilton et al. [6] found the triple hop distance test in healthy indivi-duals to be strongly correlated ( $r=$ 0.74–0.76) to an athlete’s lower extremity strength and power as measured at 180 ${}^{\circ}$ /s. However, unlike our results, Hamilton et al. [6] found correlations also at 60 ${}^{\circ}$ /s ( $r=$ 0.70–0.75). Rogers et al. [49] on the same path, found a correlation r values between 0.501 and 0.542 of the THD test with strength and power.

For the THD are interesting the differences in the correlations between the angular velocities of 60 ${}^{\circ}$ /s, 180 ${}^{\circ}$ /s and 300 ${}^{\circ}$ /s. At the 300 ${}^{\circ}$ /s we found correlations only at the extensors and at 60 ${}^{\circ}$ /s no correlations. In different speeds different muscle groups are important.

4.3 Single timed hop test

At the STH test we measure time and not distance. The results revealed moderate to good correlations of the extensors of the knee at 60 ${}^{\circ}$ /s angular velocity, at isokinetic measurements represented by the TW and AP. It is interesting to note that this positive relationship was not demonstrated at faster speeds of 180 ${}^{\circ}$ /sec and 300 ${}^{\circ}$ /sec (with only one exception) during knee extension or flexion movements and only occurred at the 60 ${}^{\circ}$ /sec test speed.

Although isokinetic dynamometer Biodex System 3 used in this study is able to calculate isokinetic variables at higher than 300 ${}^{\circ}$ /s, which could be more indicative to muscular performance, based on the study by Drouin et al. [18] concerning the validity of the results of isokinetic variables at speeds higher than 300 ${}^{\circ}$ /s we decided not to use them.

It was also thought that it would be difficult for participants, a large percentage of whom were not engaged in sports activities, to generate moment within the limits of isokinetic ROM at such high speeds. None of the assessed angular velocities appear to be more indicative to functional performance. Although the ’300 ${}^{\circ}$ /s’ has been recognized as knee velocity during normal gait [50], in our study this speed was not fast enough to simulate the joint velocity during the functional tests. The fact that we found a moderate to good correlation at the 60 ${}^{\circ}$ /s is an indication that the focus on training must not rely on fast speeds only but should include a spectrum of speeds.

5. Conclusion

Due to their high reliability, hope tests constitute a group of useful tool for clinicians in order to build and also assess rehabilitation programs. On the other hand, according to our results, hop tests could not substitute isokinetic parameters such as Mean Peak Moment, Total Work and Average Power because of the moderate correlations between the functional hop values (CKC evaluation) and the isokinetic parameters (OKC evaluation). Thus it seems that isokinetics should be used in conjunction with the functional tests for a more objective evaluation of knee muscular performance. A combination of OKC and CKC evaluation can provide better information for functional assessment and performance of the knee muscles, and for the proper organization of a muscle strength and function restoration program.

5.1 Limitations

As a correlational study, the present study involves some limitations. Generally, correlational studies present a relationship between two variables but cannot prove that one variable causes a change in another. The correlation is not equal to a causal relationship and therefore researchers must be cautious when they make causation claims [56]. Another notable limitation involves the criteria used to rank correlation coefficient values. A signifficant r value does not automatically establish a strong relationship between two variables [51] and therefore a scoring system for $r$ values had to be selected. In our study we used one classification system [47]. However, other studies have used different systems that present variations in classification [40, 52, 53, 54, 55]. Being unaware of the subtle differences may this have clinical implicatons. Finally, on the technical side, the use of a manual stop watch should be replaced by electronic means to add validity to the findings.

Footnotes

Acknowledgments

We would like to thank all the participants who took part in this study.

Conflict of interest

No benefits in any form have been or will be received form a commercial party/grant body related directly or indirectly to the subjects of this study. The authors in this research report no conflict of interest. This study does not involve any external research grant support.

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Knee isokinetic test scores and functional hop tests findings: Are they related?

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSION:

Keywords

1. Introduction

2. Methods

2.1 Subjects

Table 1 Anthropometric data and the descriptive statistics [mean, standard deviation, range] for the 25 participants

Table 2 Descriptive statistics [mean, standard deviation, range] for all functional data in dominant limbs

Table 3 Descriptive statistics of normalized to BW isokinetic parameters of PM, TW and AP at 60 ∘ /s, 180 ∘ /s and 300 ∘ /s in dominant limbs

3. Results

Table 4 Correlations between normalized to BW functional tests and isokinetic parameters

4.1 Single hop distance test

4.2 Triple hop distance test

4.3 Single timed hop test

5. Conclusion

5.1 Limitations

Footnotes

Acknowledgments

Conflict of interest

References

Table 1
Anthropometric data and the descriptive statistics [mean, standard deviation, range] for the 25 participants

Table 2
Descriptive statistics [mean, standard deviation, range] for all functional data in dominant limbs

Table 3
Descriptive statistics of normalized to BW isokinetic parameters of PM, TW and AP at 60 ${}^{\circ}$ /s, 180 ${}^{\circ}$ /s and 300 ${}^{\circ}$ /s in dominant limbs

Table 4
Correlations between normalized to BW functional tests and isokinetic parameters