Can Muscle Power Be Estimated From Thigh Bulk Measurements? A Preliminary Study

Transcription

1 Journal of Sport Rehabilitation, 1999, O 1999 Human Kinetics Publishers, Inc. Can Muscle Power Be Estimated From Thigh Bulk Measurements? A Preliminary Study Eric Maylia, John A. Fairclough, Leonard D.M. Nokes, and Michael D. Jones The purpose of this study was to assess whether measurements of thigh bulk taken with a tape measure would give an indication of muscle power. Eleven male patients, all undergoing unilateral menisectornies, performed exercises of the quadriceps and hamstring muscles during concentric loading at 60 /s. The patients were tested three times over a 12-week period: one day before the operation and 2 and 12 weeks after the operation. Thigh girth was recorded, using a conventional plastic tape measure, 10 cm from the top of the patella in each of the three test sessions. The results of this study demonstrated that muscle power cannot be predicted from thigh girth measurements. Key Words: isokinetics, menisectomy, quadriceps, hamstrings The concept of isokinetic exercise was developed by James Perrin and introduced in the scientific literature by Hislop et al. (1) and Thistle et al. (5). Isokinetic devices are commonly used to obtain measurements for physical therapy clinical practice. Isokinetic machines allow individuals to exert as much force and angular movement as they can generate up to a preset velocity, and they can be used to quantify a muscle group's ability to generate torque, or force (4). They can also be used as a rehabilitation tool by restoring the muscle group's preinjury level of strength. The main objective of this study was to analyze results taken from patients undergoing unilateral menisectomies to see if any correlation could be found between muscle power and thigh bulk. This in turn would allow muscle power to be predicted from measuring thigh girth with a tape measure, which would be very useful in the clinical field because not all clinicians have access to expensive dynamometers to monitor muscle power. Eric Maylia, Leonard D.M. Nokes, and Michael D. Jones are with the Medical Engineering Research Unit, Cardiff School of Engineering, University of Wales Cardiff, P.O. Box 917, Cardiff, Wales, CF2 IXH, UK. John A. Fairclough is with the Department of Orthopaedics and Trauma, Cardiff Royal Infirmary, Cardiff, Wales, CF2 lxh, UK.

2 Estimating Muscle Power 51 Our second objective was to analyze the statement made by Lesmes et al. in 1978 that "increases in strength resulting from isokinetics frequently occur in the absence of increases in muscle cross sectional girth and hypertrophy" (2). Subjects Method Studies were done on I1 males between 22 and 53 years of age, all undergoing unilateral menisectomies (Table 1). Before testing, the patients were informed of the procedure and risks of the study and then signed an informed consent form. Instrumentation ABritish Standard 100-cm plastic tape measure was used in this study to measure thigh bulk. A KIN/COMTM 125E dynamometer was used to measure knee extensor and flexor peak forces at a velocity of 60'1s. Sessions Measurements were taken 1 day before the operation, 2 weeks postoperation, and 12 weeks postoperation. The first postoperation test was set at 2 weeks on the advice given by the clinician as to when the patients would be able to perform isokinetic exercises on the operated leg. The second postoperation test was set at 12 weeks because it was thought that if the appropriate physiotherapy regime had been followed, Table 1 Heights and Weights of Patients Patient Height (m) Weight (kg) Mean

3 52 Maylia, Fairclough, Nokes, and Jones the patients should be back to preinjury fitness. Three physiotherapists were used throughout the study, all following the same postoperative physiotherapy regimes in terms of frequency, duration, and exercises (see the appendix for more details). Each test session took place on the same day of the week and at approximately the same time of day in an attempt to ensure consistent activity levels. Measurement of Thigh Girth Procedure The thigh girth was marked 10 cm from the top of the patella. The site was measured three times in succession using the technique described by Lohman et al. (4), and the average of the three measurements was used as the final value (3). Isometric Measurements All patients were briefed on the operation of the testing device and how to provide maximum effort during testing. The subjects were seated upright on the dynamometer bench with a strap around the waist, chest (underneath the arms), and across the mid-thigh of the leg being tested. The mechanical arm of the dynamometer was aligned with the subject's lower leg on the side that was being tested. A shin pad, attached to the distal end of the mechanical arm 25 cm from the center of rotation, was secured to the subject's limb. The axis of the knee was placed in line with the axis of rotation of the dynamometer. Each limb was weighed before testing by the KINICOM's automatic limb-weighing system; this was to correct for the gravitational effect on torque. The tests were first carried out on the uninvolved limb and then on the involved limb. The subjects were instructed to perform three submaximal (approximately 50% of maximum force) repetitions of knee extension and flexion at 60 /s between the angles of 15 and 75". The subjects then performed three maximal repetitions at 60 /s. This was to allow the subject to become familiar with the testing equipment and as a general warm-up before starting the test. After the warm-up, the subject was given a 45-s rest before being asked to perform five maximal repetitions at the same velocity and between the same angles as in the warm-up. These data were recorded and stored on a computer. Results The results obtained from the 11 patients were tabulated and are shown in Tables 2-5. The four tables show (a) thigh girth measured and force produced on the injured and uninjured quadriceps (Tables 2 and 3) and (b) thigh girth measured and force produced on the injured and uninjured hamstrings (Tables 4 and 5). The measurements that were taken 1 day before the operation were defined as Stage 1, those taken 2 weeks after the operation were defined as Stage 2, and

4 Estimating Muscle Power Table 2 Leg Strength and Thigh Girth of Quadriceps on Injured Legs, Pre- and Postoperative Measurement Stage Patient 1 (pre-op.) 2 (post-op.) 3 (post-op.) Note. A dash indicates that the patient did not return for Stage 3 of the study. those taken after 12 weeks were defined as Stage 3. Note that Patients 3,4, and 6 did not return for the third test session. Injured Leg Discussion Quadriceps. Looking at the data for Patient 1 (Table 2), a thigh girth of approximately 55 cm was noted at Stages 1,2, and 3, but the muscle force ranged from approximately 580 to 940 N, a difference of 360 N. This trend is also demonstrated by Patient 5, who had a thigh girth of approximately 61 cm over the 12-week period but showed a muscle force ranging from 260 to 800 N. This large change in force but no

5 54 Maylia, Fairclough, Nokes, and Jones Table 3 Leg Strength and Thigh Girth of Quadrieeps on Uninjured Legs, Pre- and Postoperative Measurement Stage Patient 1 (pre-op.) 2 (post-op.) 3 (post-op.) Girth (em) Note. A dash indicates that the patient did not return for Stage 3 of the study. change in thigh girth can be attributed to a number of reasons; for example, the patients were experiencing pain prior to the operation, or the patients were still unfamiliar with the equipment. In this case it was caused by the patients' experiencing pain prior to operation. After surgery, it can be seen that muscle power increased but thigh girth remained the same. Between Stages 1 and 2, Patient 4 demonstrated a decrease of over 2 cm in thigh girth but an increase of approximately 40 N in force. This could be because of a decrease in fat or a decrease in swelling postoperation. Patients 7 and 8 at Stage 3 had the same thigh gxth of 54 cm and forces of approximately 920 and 1035 N, respectively. Looking at these particular results, we can conclude that it is not possible to predict quadriceps muscle power from only measuring thigh gwth in the injured leg of a patient. These results also reiterate the statement made by Lesmes that an increase in muscle power does not necessarily mean an increase in thigh bulk (2).

6 Estimating Muscle Power Table 4 Leg Strength and Thigh Girth of Hamstrings on Injured Legs, Pre- and Postoperative Measurement Stage Patient I (pre-op.) 2 (post-op.) 3 (post-op.) Note. A dash indicates that the patient did not return for Stage 3 of the study. Analyzing the results obtained from Patients 9 and 10 (Table 2), we see that they show an increase in both muscle power and thigh girth over the 12-week testing period. This is at variance with the work of Lesmes (2). Comparing these two patients, we can see that the force varied considerably even though the thigh girth remained approximately the same-hence, muscle power cannot be predicted from thigh girth when comparing results between patients. Hamstrings. For the majority of patients, the same trends can be seen in Table 4 as were seen in Table 2; that is, it is not possible to predict muscle power from thigh girth on the injured leg. These results also reiterate the statement by Lesmes (2). However, in analyzing the results from Patients 9 and 10 (Table 4), we can see that the strength of the hamstrings increased at the same time that an increase of thigh girth was noted. This could mean that muscle power could be

7 56 Maylia, Fairclough, Nokes, and Jones Table 5 Leg Strength and Thigh Girth of Hamstrings on Uninjured Legs, Pre- and Postoperative Measurement Stage Patient 1 (pre-op.) 2 (post-op.) 3 (post-op.) 1 Note. A dash indicates that the patient did not return for Stage 3 of the study. predicted from thigh girth for these individual patients. However, the results actually show that, although both these patients had increased thigh girth and muscle power, the thigh girths for both patients were similar (55 and 54 cm, respectively, on average), but their muscle power varied greatly (576 and 474 N, respectively, on average). Therefore, Patient 10's muscle power could not have been predicted using the thigh girth measurement and corresponding it to that of Patient 9, and vice versa. Table 5 shows that the values of muscle power for the uninjured hamstrings of Patients 9 and 10 did not correspond to their thigh girths, so the hypothesis that increases in thigh girth and muscle power correspond does not hold true. Therefore, it is unlikely that it is possible to predict muscle power from thigh girth for these two patients.

8 Estimating Muscle Power 57 Uninjured Leg Quadriceps. From Table 3, it can be seen that Patients 5 and 8 maintained approximately the same individual thigh girth but had varying values for force. For example, throughout the study Patient 5 had an almost continuous thgh grrth of approximately 61 cm, but the values of muscle force ranged from approximately 590 N (Stage 1) to 920 N (Stage 3). This is corroborated by the results for Patient 8, who had a thigh girth of approximately 53 cm throughout the study but whose muscle force ranged from 1,032 N (Stage 1) to 1,275 N (Stage 3). There were a number of patients who showed an increase in force over the 12-week testing period but showed no increase in thigh girth; this corresponds with the statement made by Lesmes and implies that muscle force cannot be predicted from thigh girth (2). Hamstrings. In Table 5, we see that Patient 1 showed an increase in force and thigh girth between Stages 1 and 2 but then a decrease in force and thigh girth between Stages 2 and 3. Hence, for this patient it may be possible to predict muscle power from Patient 3 also showed an increase in thigh guth and muscle power between Stages 1 and 2, but unfortunately this patient did not return at Stage 3, so these results are inconclusive. The other patients all had similar but very different muscle force values. From the small sample size, the results imply that muscle power cannot be predicted from thigh girth, and they also agree with the statement made by Lesmes (2). However, a larger trial needs to be undertaken to further test the hypothesis. Conclusion Because this research was carried out on a small sample, a larger trial needs to be undertaken to validate these preliminary findings. Judging from the small sample size, there appears to be no correlation between muscle power and thigh girth individually or as a group. Reasons for this could include the possibility that increases in thigh girth were caused by a number of factors, for example, swelling and an increase in subcutaneous fat, as opposed to an increase in muscle mass. It could also be due to the wide variation in the subjects used in this study; for example, they participated in different sporting activities, were of different ages, and so on. With reference to the statement made by Lesmes (2), "increases in strength resulting from isokinetics frequently occur in the absence of increases in muscle cross sectional girth and hypertrophy," the results show that this statement holds true for the majority of patients in this small study. A more detailed study looking at individual sports groups-for example, 100-m runners only or football players only-may show a correlation between muscle power and muscle bulk. Further study may involve the use of skinfold measurements taken at the same position on the thigh as those of thigh girth. This would then resolve in a set of equations, as in calculating % body fat from skinfolds, that could be used to predict muscle power without using a dynamometer.

9 References Maylia, Fairclough, Nokes, and Jones 1. Hislop, H., and J.J. Pemn. The isokinetic concept of exercise. Phys. Ther. 47: , Lesmes, G.R., D.L. Costill, E.F. Coyle, and W.J. Fink. Muscle strength and power changes during maximal isokinetic training. Med. Sci. Sports Exerc. 10: , Lohman, T.G., A.F. Roche, and R. Martorell (Eds.). Anthropometric Standardization Reference Manual (abridged ed.). Champaign, IL: Human Kinetics, Pemn, D.H. Isokinetic Exercise arzddssessment. Champaign, IL: Human Kinetics, Thistle, H.G., H.J. Hislop, M. Moffroid, and E.W. Lohman. Isokinetic contraction: A new concept of resistive exercise. Arch. Phys. Med. Rehab. 48: , Appendix A Physiotherapy Each patient received the same physiotherapy regimes during this study. The patients were first shown how to undertake the exercises described in Table A1 on the next page. After 2 weeks the patients performed isokinetic exercises on a dynamometer. All patients undertook submaximal repetitions of knee extensions and flexion at 60'1s between the angles of 15 and 75".

10 Estimating Muscle Power Table A1 Exercise Regime Name of exercise Exercised muscle group Description of exercise Number of repetitions Hip and knee Hip and knee Close chain Hip and knee Hip and knee Passive range of motion knee flexion Strengthening wall sides Sitting VMO selfbiofeedback Strengthening: hamstring sets Quad set in slight flexion Sit down on the floor against a wall. With towel around around heel, gently pull upward with towel until stretch is felt. Leaning on wall, slowly lower buttocks toward floor until thighs are parallel to floor. Hold for 10 s. Tighten thigh muscle as you return to starting position. Sitting, place one hand on thigh muscle just above knee, inside, other hand on thigh muscle just below hip, outside. Contract thigh muscle so inside of thigh is tight and outside is relaxed. Hold for 10 s. Sit, with legs flat, on the floor or a table. With foot turned inward, tighten muscles on back of thigh by pulling heel down into floor or table. Hold for 8 s. Sitting on the floor with legs outstretched, place a rolledup towel underneath the knee, gently tense muscle on top of thigh. Hold for 10 s. Do 8 reps.1set. Do 3 setslsession. Do 2 sessionslday. Repeat 3 times. Do 3 sessionslday. Do 8 reps. Do 3 sessionslday. Repeat 3 times. Do 3 sessionslday. Do 8 reps. Do 3 setslsession. Do 3 sessionslday.