1. Intraclass Correlation Coefficients
Bryanne Bellovary1, Caitlin Glendenning1, Alexander R. Wolfe1, Erich J. Petushek1,2, Sarah K. Leissring1,
Mitchell L. Stephenson1, Erika Purdy1, Bailey M. Hagner1, Randall L. Jensen, FACSM1.
1Northern Michigan University, Marquette, MI. 2Michigan Technological University, Houghton, MI
Comparison of Isotonic and Isokinetic Measurements of Extension/Flexion Strength and Quadriceps-Hamstring Ratio.
American College of Sports Medicine
Annual Meeting 2012
San Francisco, California USA
Abstract
Isokinetic dynamometry assessment is considered the gold standard for quantifying quadriceps-hamstring ratio (Q/H), but at significant financial cost. Isotonic strength equipment such as flexion and extension weight machines are less expensive and may be a valid alternative for assessing Q/H. PURPOSE: To assess the relationship between 5 RM knee extension/flexion load and maximum Q/H torque ratios assessed using isotonic and isokinetic resistance machines, respectively. METHODS: 21 Division II women soccer players (Mean ± SD Age = 19.9 ± 1.0 years; Height = ± 7.2 cm; Mass = 63.0 ± 7.1 kg) were assessed for strength measures of the right leg. Knee extension/flexion strength was assessed using isotonic weight machines. Following appropriate warm up sets and two minutes rest, a 5 RM was attempted for each knee extension and flexion. Resistance was increased kg per set after 2 minutes rest until 5 RM was attained. A Biodex System 4.0 isokinetic dynamometer was used to assess peak torque of knee extension/flexion at 300 degrees/s. A self-selected 5 rep warm up was performed, followed by one minute rest; 10 reps were then performed at maximum. A Paired T-test and Intraclass Correlation analysis were used to compare knee extension/flexion strength and Q/H between the two measurement protocols. RESULTS: Neither leg extension or leg flexion were different between the isotonic weight machine and the Biodex. Mean values for the flexion conditions were ± 8.89 kg for weight machine and ± 9.46 Nm for the Biodex; the extension conditions had mean values of ± kg and Nm respectively. The Biodex Q/H was ± while the weight machine ratio was ± Intraclass Correlation Coefficients between the two pairs were r = for the flexion pair, r = for the extension pair, and r = for Q/H. CONCLUSION: Due to a significant difference and moderate correlation between measurement protocols, isotonic weight machines should not be used to determine Q/H ratio. Variations in speed, range of motion and number of repetitions completed reps may all have influenced the differences between isotonic and isokinetic measurements.
Figure 1. Northern Michigan University’s Biodex System 4.0 (left) and extension/flexion weight machine (right)
METHODS
Twenty-one Division II women soccer players (Mean ± SD Age = 19.9 ± 1.0 years; Height = ± 7.2 cm; Mass = 63.0 ± 7.1 kg) were assessed for strength measures of the right leg. Knee extension/flexion strength was assessed using isotonic weight machines (extension/flexion machine, Sorinex, Following appropriate warm up sets and two minutes rest, a 5 RM was attempted for each knee extension and flexion. Resistance was increased kg per set after 2 minutes rest until a 5 RM was attained based off of Baechle & Earle (2008) protocol for estimating 1-RM. A Biodex System 4.0 isokinetic dynamometer (Biodex Medical Systems; Shirley, New York) was used to assess peak torque of knee extension/flexion at 300 degrees/s. A self-selected 5 repetition warm up was performed, followed by one minute rest; 10 repetitions were then performed at maximum. A Paired T-test and Intraclass Correlation analysis were used to compare knee extension/flexion strength and Q/H between the two measurement protocols. During both the isokinetic dynamometry and 5 RM extension/flexion strength tests, subjects were verbally encouraged to perform maximally.
RESULTS
Neither leg extension or leg flexion were different between the isotonic weight machine and the Biodex. Mean values for the flexion conditions were ± 8.89 kg for the weight machine and ± 9.46 Nm for the Biodex; the extension conditions had mean values of ± kg and ± 9.71 Nm respectively. The Biodex Q/H ratio was ± while the weight machine ratio was ± Intraclass Correlation Coefficients between the two pairs were r = for the flexion pair, r = for the extension pair, and r = for Q/H.
DISCUSSION-CONCLUSION
Due to a significant difference and only moderate correlation between measurement protocols, isotonic weight machines using five repetition maximum to estimate 1-RM should not be used to determine Q/H ratio. Knapik et al. noted that some studies found lower relationships among isotonic and isokinetic strength tests due to not accounting for posture of the subjects and range of motion while performing the tests.3 Another point mentioned by Söderman & Lindström is that isotonic tests provide approximate values compared to isokinetic values which are more exact values.4 With this approximation already in a 1-RM test, to estimate a 1-RM by using a five repetition maximum protocol would have yielded more variations and so potentially leading to the significant difference and only moderate correlation, as found in the present study. Until isotonic weight machines can yield more exact values, quadriceps-hamstring ratios should continue to be measured using one-repetition maximum testing if done isotonically.
INTRODUCTION
Isokinetic dynamometry assessment is considered the gold standard for quantifying quadriceps-hamstring ratio (Q/H).5 Dynamometry is generally applied to validate other strength assessment procedures,5 but at a significant financial cost. A possible alternative for strength evaluation for Q/H could be the 1-RM test which is the most used assessment of dynamic strength, since it is a practical method, low cost and relatively safe for most populations.1 The correlations between 1-RM testing and dynamometry are generally high, implying the validity of 1-RM testing for strength assessment.5 1-RM testing has also been shown to be a reliable method for the assessment of muscle strength in both the young and elderly.4 It should be noted however, isokinetic dynamometry provides more exact values for muscle strength compared to isotonic weight machines, which yield more approximate values.4 With literature referencing the validity and reliability of 1-RM testing and its high correlation with dynamometry, isotonic strength equipment such as flexion and extension weight machines may be a valid alternative for assessing Q/H.
Américo et al. used the 1-RM test in the measurement of Q/H.1 Baechle & Earle state that a common strategy when using assistant exercises, such as knee extension/flexion exercises, multiple-RM testing should be used and then estimate the 1-RM.2 Although Wong et al.6 used squat testing, a core exercise, they found that a 6-RM squat load was an accurate means of predicting training loads. It might be possible to perform a 5-RM submaximal protocol with knee extension/flexion weight machines in the present study to accurately estimate 1-RM. Therefore, the purpose of this study was to assess the relationship between 5 RM knee extension/flexion load and maximum Q/H torque ratios assessed using isotonic and isokinetic resistance machines, respectively.
Table 1: Mean strength values for flexion and extension and : Quadriceps – hamstring ratio (Q/H) on the Biodex System 4.0 and the weight machine
Flexion
Extension
Q/H
Biodex
58.90 ± 9.46 Nm Nm
0.782 ± 0.152
Weight Machine
64.88 ± 8.89 kg
77.98 ± kg
0.850 ± 0.158
REFERENCES
1. Américo, S. P. F., Vinícius de Souza, V., Guimarães, C. Q. & Rolla, A. F. L. (2011). Use of 1-RM Test in the Measurement of Knee Flexors and Extensors Ratio in Young Adults. Revista Brasileira de Medicina do Esporte. 17(2):
2. Baechle, T. R. & Earle, R. W. (2008). Essentials of Strength Training and Conditioning Third Edition. National Strength and Conditioning Association. Human Kinetics
3. Knapik, J. J., Wright, J. E., Mawdsley, R. H. & Braun, J. M. (1983). Isokinetic, Isometric and Isotonic Strength Relationships. Archives of Physical Medicine and Rehabilitation. 64(2):
4. Söderman, K. & Lindström, B. (2010). The relevance of using isokinetic measures to evaluate strength. Advances in Physiotherapy. 12:
5. Verdijk, L. B., Van Loon, L., Meijer, K. & Savelberg, H. H. C. M. (2009). One-repetition maximum strength test represents a valid means to assess leg strength in vivo in humans. Journal of Sports Sciences. 27(1):
6. Wong, D. P., Tan, E. C. H., Chaouachi, A., Carling, C., Castagna, C., Bloomfield, J. & Behm, D. G. (2010). Using Squat Testing to Predict Training Loads for Lower-Body Exercises in Elite Karate Athletes. Journal of Strength and Conditioning Research. 24(11):
Table 2: Intraclass Correlation Coefficients between the Biodex System 4.0 and the weight machine for flexion, extension and quadriceps to hamstring ratio (Q/H)
Intraclass Correlation Coefficients
Flexion
0.745
Extension
0.874
Q/H
0.663
ACKNOWLEDGEMENT: Sponsored in part by University Scholars and Student Travel Grants from Northern Michigan University