Stephen J. Kinzey

The Effect of a Simulated Knee Joint Effusion on Postural Control in Healthy Subjects

OBJECTIVE To determine the effects of a simulated knee joint effusion on center of pressure (COP) path and mean power frequency (MPF) during standing. DESIGN Quasi-experimental design. SETTING Sports injury research laboratory in a university setting. PARTICIPANTS Twenty healthy volunteers, 10 of whom (age, 20.1+/-2.4y; height, 168.0+/-8.1cm; weight, 70.4+/-13.3kg) were assigned to an effusion group and 10 of whom (age, 25+/-3.8y; height, 169.4+/-8.9cm; weight, 74.7+/-7.7kg) were assigned to a control group. INTERVENTIONS COP data were collected before and after a 60-mL injection of sterile saline into the knee joint space. MAIN OUTCOME MEASURES COP path and mediolateral and anteroposterior MPF. RESULTS COP path decreased after the effusion (pre-effusion mean, 92.2+/-21.9cm; posteffusion mean, 77.27+/-23.0cm). No change was found within the control group for COP path (P>.05). No differences were detected before or after joint effusion when the MPF was examined (P>.05). CONCLUSIONS Possible explanations for the improved postural control after the effusion include additional somatosensory feedback, an augmented neural drive to the soleus, and/or increased capsular tension.

Acute Effects of a Single Bout of Resistance Exercise on Postural Control in Elderly Persons

Many elderly persons are engaging in resistance exercise to counter muscle atrophy due to aging. Here, the acute effects of resistance exercise on postural control mechanisms were examined. Postural control was quantified by mean square center-of-pressure displacements were calculated utilizing force vectors in accordance with previously developed equations. Stabilogram-diffusion plots utilized the displacements as data points after curve-fitting techniques were applied. Two regions, representing the open-loop and closed-loop postural control mechanisms, are shown by the plots and separated at the critical point, which represents the shift in control mechanisms. 21 older adults (age M = 71.2, SD = 3.84, range 66–81 years) performed three sets of 10–12 repetitions for six resistance exercises for the lower extremity until fatigue. Immediately after exercise, postural stability was reduced. This was represented by a shift of the critical point to the right, indicating an increase in open-loop control. Since resistance training has an acute negative effect on postural control, it is advised to assist elderly clients carefully and immediately after resistance training.

Excess postexercise oxygen consumption following acute aerobic and resistance exercise in women who are lean or obese.

&NA; Crommett, A.D., and S.J. Kinzey. Excess postexercise oxygen consumption following acute aerobic and resistance exercise in women who are lean or obese. J. Strength Cond. Res. 18(3):410–415. 2004.—Seventeen women were divided into lean (19.5 ± 0.5 years; 22.2 ± 0.6 kg·m‐2) and obese (20.4 ± 0.5 years; 34.9 ± 2.1 kg·m‐2) groups. On completion of a submax cycle ergometer test and 10‐repetition maximum (10RM) of 5 exercises on a Smith machine, subjects returned for 2 exercise sessions during menses. Session 1 consisted of performing 3 sets of 10 repetitions at 70% of the predetermined 10RM for the following exercises: squat, calf raises, bench press, upright row, and shoulder press. Session 2 consisted of cycling at 60–65% SymbolO2max for a duration that would expend the same number of calories as the resistance session. Postexercise respiratory exchange ratio and EPOC magnitude/duration were similar for both groups. These findings indicate that women who are lean or obese will respond similarly to exercise at similar relative intensities and that aerobic and resistance exercise of equal caloric expenditure will elicit similar EPOC responses. Symbol. No caption available.

Kinetic Comparison of Free Weight and Machine Power Cleans

Jones, RM, Fry, AC, Weiss, LW, Kinzey, SJ, and Moore, CA. Kinetic comparison of free weight and machine power cleans. J Strength Cond Res 22(6): 1785-1789, 2008-The purpose of this investigation was to compare the kinetic characteristics of the power clean exercise using either free weight or machine resistance. After familiarization, 14 resistance trained men (mean ± SD; age = 24.9 ± 6.2 years) participated in two testing sessions. During the initial testing session, one-repetition maximum performance (1RM) was assessed in either the free weight or machine power clean from the midthigh. This was followed by kinetic assessment of either the free weight or the machine power clean at 85% of 1RM. One week after the initial testing session, 1RM performance, as well as the subsequent kinetic evaluation, were performed for the alternate exercise modality. All performance measures were obtained using a computer-interfaced FiTROdyne dynamometer (Fitronic; Bratislava, Slovakia). Maximum strength (1RM) and average power were significantly greater for the free weight condition, whereas peak velocity and average velocity were greater for the machine condition (p < 0.05). Although peak power was not different between modalities, force at peak power (free weights = 1445 ± 266 N, machine = 1231 ± 194 N) and velocity at peak power (free weights = 1.77 ± 0.28 m·s−1, machine = 2.20 ± 0.24 m·s−1) were different (p < 0.05). It seems that mechanical limitations of the machine modality (i.e., lift trajectory) result in different load capacities that produce different kinetic characteristics for these two lifting modalities.