Scott H. Leggett

Injuries and adherence to walk/jog and resistance training programs in the elderly.

To evaluate the effects of 26 wk of aerobic and resistance training on the incidence of injury and program adherence in 70- to 79-yr-old men and women, 57 healthy volunteers (25 males, 32 females) were randomly assigned to a walk/jog (W/J, N = 21), strength (STREN, N = 23), or control (CONT, N = 13) group. Walk/jog training was for 30-45 min, 3 d.wk-1 with intensity equal to 40-70% heart rate max reserve (HRmax reserve) during the first 13 wk, and 75-85% HRmax reserve for weeks 14-26. STREN training consisted of one set (10-12 repetitions) each of 10 variable resistance exercises performed to volitional fatigue. Forty-nine of the original participants completed the training program. Walk/jog training increased VO2max from 22.5 to 27.1 ml.kg-1.min-1 (P less than or equal to 0.05) while STREN and CONT showed no change. STREN improved significantly in chest press and leg extension strength (P less than or equal to 0.05) while W/J and CONT showed no change. Adherence to training was 20/23 (87%) and 17/21 (81%) in STREN and W/J, respectively. One repetition maximum (1-RM) strength testing resulted in 11 injuries in the 57 subjects (19.3%) while STREN training resulted in only two injuries in 23 subjects (8.7%). Walk training during weeks 1-13 resulted in one injury in 21 subjects (4.8%). Eight of 14 subjects (57%) who began jogging intervals at week 14 incurred an injury: two of eight (25%) of the men and all of the women (6 of 6). All W/J training injuries were to the lower extremity.(ABSTRACT TRUNCATED AT 250 WORDS)

Lumbar strengthening in chronic low back pain patients. Physiologic and psychological benefits.

The effects of exercise for isolated lumbar extensor muscles were examined in 54 chronic low-back pain patients. Subjects were randomly assigned to a 10-week exercise program (N =31) or a wait-list control group (N = 23). Results indicated a significant increase in isometric lumbar extension strength for the treatment group and a significant reduction in reported pain compared with the control group (P 0.05). Treated subjects reported less physical and psychosocial dysfunction whereas the control group increased in pain, and physical and psychosocial dysfunction. There were no concomitant changes in reported daily activity levels. These results show that lumbar extension exercise is beneficial for strengthening the lumbar extensors and results in decreased pain and improved perceptions of physical and psychosocial functioning in chronic back pain patients. However, these improvements were not related to changes in activities or psychological distress.

Effect of training frequency and specificity on isometric lumbar extension strength

To investigate the effects of training frequency and specificity of training on isolated lumbar extension strength, 72 men (age = 31 +/- 9 years) and 42 women (age = 28 +/- 9 years) were tested before and after 12 weeks of training. Each test involved the measurement of maximum voluntary isometric torque at 72 degrees, 60 degrees, 48 degrees, 36 degrees, 24 degrees, 12 degrees, and 0 degrees of lumbar flexion. After the pretraining tests, subjects were randomly stratified to groups that trained with variable resistance dynamic exercise every other week (1X/2 weeks, n = 19), once per week (1X/week, n = 22), twice per week (2X/week, n = 23) or three times per week (3X/week, n = 21); a group that trained isometrically once per week (n = 14); or a control group that did not train (n = 15). Analysis of covariance showed that all training groups improved their ability to generate isometric torque at each angle measured when compared with controls (P less than 0.05). There was no statistical difference in adjusted posttraining isometric torques among the groups that trained (P greater than 0.05), but dynamic training weight increased to a lesser extent (P less than 0.08) for the 1X/2 weeks group (26.6%) than for the groups that trained 1X/week, 2X/week, and 3X/week (37.2 to 41.4%). These data indicate that a training frequency as low as 1X/week provides an effective training stimulus for the development of lumbar extension strength. Improvements in strength noted after isometric training suggest that isometric exercise provides an effective alternative for developing lumbar strength.

Quantitative assessment of full range-of-motion isometric lumbar extension strength.

The purpose of this study was to evaluate the reliability and variability of repeated measurements of isometric (IM)lumbar extension (LB EXT) strength made at differnt joint angles. Fifty-six men (age, 29.4 ± 10.7 years) and 80 women (age, 24.3 ± 9.1 years) completed IM LB EXT strength tests on 3 separate days (D1, D2, and D3). On D1 and D2, subjects completed two tests (T1 and T2) separated by a 20-to 30-minute rest interval. For each test, IM LB EXT strenth was measured at 72, 60, 48, 36, 24, 12, and 0° of lumbar extension. Mean IM strength values, within-day reliability coefficients, and test variability over the seven angles improved from D1 to D2 (D1: mean, 160.0 to 304.1 N · m, r=0.78 to 0.96, SEE = 37.6 to 46.9 N · m; D2: mean, 176.3 to 329.1 N · m, r = 0.94 to 0.98, SEE = 29.0 to 34.4 N · m). Mean strength values leveled off by D3 (174.5 to 317.0 N · m). The most reliable test results showed that the IM LB EXT strength curves were linear and descending from flexion to extension and ranged from 235.8 ± 85.2 to 464.9 ± 150.7 N · m for men (extension to flexion) and from 134.6 ± 53.2 to 237.3 ± 71.9 N. m for women. Lumbar extension strength was clearly greatest in full flexion, which is in contrat to previously reported results. One practice test was required to attain the most accurate and reliable results. These data indicate that repeated measures of IM LB EXT strength are highly reliable and can be used for the quantification of IM LB EXT strength through a range of motion.

Effect of resistance training on lumbar extension strength

Development of a new testing machine, which stabilizes the pelvis, allowed us to evaluate the lumbar extensor muscles before and after training. Fifteen healthy sub jects (29.1 ± 8 years of age) trained 1 day per week for 10 weeks and 10 healthy subjects (33.7 ± 16 years of age) acted as controls. Training consisted of 6 to 15 repetitions of full range of motion variable resistance lumbar extension exercise to volitional fatigue and periodic maximal isometric contractions taken at seven angles through a full range of motion. Before and after the 10 week training period, subjects completed a maximum isometric strength test at seven angles through a 72° range of motion (0°, 12°, 24°, 36°, 48°, 60°, and 72° of lumbar flexion). The training group significantly improved in lumbar extension strength at all angles (P ≤ 0.01). The result at 0° (full extension) showed an increase from 180.0 ± 25 Nm to 364.1 ± 43 Nm (+102%) and at 72° (full flexion) from 427.4 ± 44.1 to 607.4 ± 68 (+42%) Nm. Results from the control group showed no change (P ≥ 0.05). The mag nitude of gain shown by the training group reflects the low initial trained state of the lumbar extensor muscles. These data indicate that when the lumbar area is iso lated through pelvic stabilization, the isolated lumbar extensor muscles show an abnormally large potential for strength increase.

Effect of training on the relationship between maximal and submaximal strength.

The purpose of this study was to evaluate the validity of a dynamic seven to 10 repetition maximum (7-10 RM) test to estimate maximal knee extension strength (1-RM) in untrained and trained subjects. Thirty-three men and 25 women (25 +/- 5 yr) were randomly assigned to a group that trained two or three times.wk-1 for 18 wk (N = 47) or a control group (N = 11). Training included one set of 7-10 repetitions to volitional fatigue on a Nautilus knee extension machine. Prior to (T1) and after training (T2) dynamic strength was evaluated by 1-RM and 7-10 RM tests. The 7-10 RM test consisted of one set of variable resistance knee extension exercise performed to volitional fatigue with a weight that allowed 7-10 repetitions. The training group improved their 1-RM and 7-10 RM strength (by 31.7 and 51.4%, respectively) (P < or = 0.01) while the control group did not change. Training increased relative 7-10 RM strength (68.4% of 1-RM at T1 and 79.1% of 1-RM at T2) (P < or = 0.01). The relationship between the 7-10 RM weight and 1-RM at T1 was linear: 1-RM = 1.554 (7-10 RM weight)-5.181; R2 = 0.89; SEE = 9.3 kg. Application of this equation following training resulted in a systematic overprediction (p < or = 0.01) of 1-RM (21.2 kg) in trained subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between myoelectric activity, strength, and MRI of lumbar extensor muscles in back pain patients and normal subjects.

Eight normal individuals and eight patients with chronic back pain were evaluated. They undertook a treatment program lasting 8 weeks, with two exercise sessions each week. Myoelectric activity, lumbar extensor strength, and cross-sectional magnetic resonance imaging appearance of the lumbar paraspinal extensor muscles was assessed at the beginning and end of the program. Initial baseline and final extensor strength measurements were done isometrically at seven points through full range. Surface myoelectric activity was monitored during both flexion and extension exercise. Subsequently, electromyographic (EMG) signals were analyzed for mean frequency (MPF) and amplitude (RMS). An average functional improvement of 65% and reduction of pain complaint of 41% occurred in the eight patients with chronic low back pain. Extensor strength improved an average of 48% contrasted to 6% for the normal subjects. Four patients who showed severe fatty infiltration in the extensors had a decrease in the degree of infiltration and no change in muscle mass. Changes in fatty infiltration did not correlate with strength changes. The dynamic EMG changes documented a decrease in amplitude (RMS) and a smaller decrease in frequency (MPF) for the same resistance when used at the beginning and end of the program. Structural changes in the muscles are not always needed to achieve strength gains or symptomatic improvement.

Specificity of limited range of motion variable resistance training.

The present study evaluated the effect of limited range of motion (ROM) variable resistance training on full ROM strength development. Twenty-eight men and 31 women were randomly assigned to one of the three training groups (A, B, AB) or a control group (C). A, B, and AB performed variable resistance bilateral knee extension exercise 2 (N = 25) or 3 (N = 19) d.wk-1 for 10 wk with an amount of weight that allowed one set of 7-10 repetitions. Group A trained in a ROM limited to 120 degrees to 60 degrees of knee flexion. Group B trained in a ROM limited to 60 degrees to 0 degrees of knee flexion. Group AB trained full ROM. Prior to and immediately following training, isometric knee extension strength was evaluated at 9 degrees, 20 degrees, 35 degrees, 50 degrees, 65 degrees, 80 degrees, 95 degrees, and 110 degrees of knee flexion with a Nautilus knee extension tensiometer. Reliability coefficients for repeated measurements of isometric strength at multiple joint angles were high (r = 0.86-0.95, P less than 0.01; SEE = 23.1-37.2 N.m). Compared to the control group, all training groups improved in isometric strength (P less than 0.01 at each angle tested except for group A at 9 degrees and 20 degrees of knee flexion and group B at 95 degrees of flexion. Isometric strength gains for group AB were similar throughout the full ROM. Isometric strength gains for the limited ROM trained groups were greater in the trained ROM than in the untrained ROM (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of reduced frequency of training and detraining on lumbar extension strength

To investigate the effect of reduced frequency of training and detraining on lumbar extension strength, 50 subjects (34 men, aged 34 ± 11yrs; and 16 women, aged 33 ± 11yrs) were recruited from ongoing strength training programs. Initial training consisted of 10 or 12 weeks of variable resistance lumbar extension strength exercise to volitional fatigue 1, 2 or 3 times a week. After the initial training, subjects reduced the frequency of training to once every 2 weeks (n = 18) or once every 4 weeks (n = 22) for 12 weeks. Only the frequency of training was changed; the mode, volume, and intensity of exercise remained constant for both reduced frequency of training groups. An additional ten subjects terminated training and acted as controls (detraining group). Isometric lumbar extension strength was evaluated at seven angles through a 72 degree range-of-motion before training, after training, and after reduced frequency of training or detraining. Analysis of variance with repeated measures indicated that lumbar extension strength improved P ≤ 0.05) for all groups after the initial to or 12 weeks of training. After 12 weeks of training, the once every 2 weeks and once every 4 weeks groups showed no significant reduction in lumbar extension strength at any angle tested, whereas the detraining group demonstrated an average 55% reduction in strength. These findings indicate that isometric lumbar extension strength can be maintained for up to 12 weeks with a reduced frequency of training as low as once ovary 4 weeks when the intensity and the volume of exercise are maintained.

Frequency and volume of resistance training : effect on cervical extension strength

Quantification of cervical extension (CERV EXT) strength is complicated by the inability to stabilize the torso and isolate the CERV EXT muscles. A newly developed machine designed to stabilize the torso and isolate the CERV EXT muscles was used to evaluate the effect of frequency and volume of resistance training on CERV EXT strength. Fifty men (age, 26 +/- 9 years; height, 174 +/- 16 cm; weight, 74 +/- 9 kg) and 28 women (age, 30 +/- 9 years; height, 152 +/- 32 cm; weight, 62 +/- 7 kg) volunteered to participate. Subjects were randomly stratified to one of four training groups or a control group (CONT, n = 19) that did not train. Each training group exercised for 12 weeks as follows; once per week using one set of dynamic exercise (DYN 1x/wk, n = 14), once per week using one set of DYN and one set of maximal isometric (IM) exercise at eight angles through a 126 degrees-range of CERV EXT (DYN-IM 1x/wk, n = 16), DYN 2x/wk (n = 19), or DYN-IM 2x/wk (n = 10). Maximal IM torque was measured at eight angles initially and after 12 weeks of training. All training groups improved CERV EXT strength (p < or = 0.05) at all angles tested compared to the CONT except for DYN once per week at 0 degree of CERV flexion. A greater increase in strength was found when the groups that trained two times a week were compared to those that trained once per week.(ABSTRACT TRUNCATED AT 250 WORDS)