Weeks Of Progressive Resistance Training Research Articles

Effects of progressive resistance training on the contractile function of permeabilized single muscle fibers from the vastus lateralis muscle of older women

The purpose of this study was to determine the effects of 12 weeks of progressive resistance training with shortening contractions on the function of permeabilized single muscle fibers obtained from biopsies of vastus lateralis (VLT) muscle of older women (n=16, 70–85 yrs). Ten fast (type IIa) and ten slow (type I) fibers were analyzed from each pre- and post-training VLT biopsy. Each fiber was analyzed for cross-sectional area (CSA), specific force (sFo), and normalized power (nPmax). Following 12 weeks of training, the slow fibers from trained VLT did not differ in any of the parameters measured compared with fibers from pre-trained VLT. In contrast, the fast fibers responded to the 12 week training protocol by having a 9% increase in mean sFo (P=0.001) and a 10% increase in mean nPmax (P=0.04). CSA of the fast fibers was unaffected by the training protocol. In conclusion, 12 weeks of progressive resistance training with shortening contractions improved the contractile function of the fast fibers obtained from the VLT muscles of old women. Supported by the Michigan Life Sciences Corridor.

Progressive resistance training temporarily alters hamstring torque–angle relationship

To examine the effects of eccentric and concentric progressive resistance training on muscle torque-angle relationship, 30 young adults were randomly allocated into three groups of 10, control (CTL), eccentric training (ECC) and concentric training (CON). The ECC and CON groups performed seven sessions over 3 weeks of progressive resistance training of the right hamstrings muscle, using a standard barbell and a leg curl machine. Torque-angle relationship was measured before and 4, 11 and 18 days after the end of training. Voluntary isometric torque was recorded at seven test angles, with the subject prone (20-80 degrees; 0 degrees is full extension). In the CON group, the angle of peak isometric torque increased from 46.0 +/- 5.2 degrees pre-training to 53.0 +/- 14.9 degrees on day 4 following training (P<0.05). In the ECC group, peak torque was increased over baseline on days 4 and 11 post-training, particularly at extended knee angles (P<0.05). The angle at which peak torque occurred was decreased on day 4 (50.0 +/- 8.2 degrees pre-training, 29.0 +/- 7.4 degrees on day 4) and on day 11 (both P<0.01), but was similar to baseline 18 days after training. ECC therefore induced a temporary change in torque-angle relationship.

Age-related differences in rapid muscle activation after rate of force development training of the elbow flexors

In young adults, improvements in the rate of force development as a result of resistance training are accompanied by increases in neural drive in the very initial phase of muscle activation. The purpose of this experiment was to determine if older adults also exhibit similar adaptations in response to rate of force development (RFD) training. Eight young (21-35 years) and eight older (60-79 years) adults were assessed during the production of maximum rapid contractions, before and after four weeks of progressive resistance training for the elbow flexors. Young and older adults exhibited significant increases (P<0.01) in peak RFD, of 25.6% and 28.6% respectively. For both groups the increase in RFD was accompanied by an increase in the root mean square (RMS) amplitude and in the rate of rise (RER) in the electromyogram (EMG) throughout the initial 100 ms of activation. For older adults, however, this training response was only apparent in the brachialis and brachioradialis muscles. This response was not observed in surface EMG recorded from the biceps brachii muscle during either RFD testing or throughout training, nor was it observed in the pronator teres muscle. The minimal adaptations observed for older adults in the bifunctional muscles biceps brachii and pronator teres are considered to indicate a compromise of the neural adaptations older adults might experience in response to resistance training.

Cytokine Levels After Eight Weeks of Progressive Resistance Training in Multiple Sclerosis Patients

1057 Multiple sclerosis (MS) is an autoimmune disease characterized by elevated levels of inflammatory cytokines. Recently, exercise training has been found to modulate the concentration of circulating inflammatory markers. PURPOSE: To determine whether eight weeks of progressive resistance training would alter resting cytokine levels in MS individuals. METHODS: Six ambulatory MS patients (age = 46 ± 11 yrs) volunteered for twice weekly training sessions. The resistance training exercises included knee flexion, knee extension and plantar flexion. The resistance was increased by 2–5% when the subjects were able to complete 15 repetitions in consecutive sessions. Blood was obtained by venipuncture in fasting subjects before and after the 8-week experimental period. Blood samples were stored at −80°C until analysis. Pro- and anti-inflammatory cytokines were analyzed with ELISA kits. RESULTS: Resting pro-inflammatory cytokine levels of interleukin (IL)-2 decreased 4% after training, but it was not statistically significant (4.72 ± 1.2 pg/ml vs. 4.5 ± 1.2 pg/ml, p>0.05); tumor necrosis factor-alpha decreased 10% (5.16 ± 1.32 pg/ml vs. 4.16 ± 1.32 pg/ml, p>0.05) and interferon-gamma decreased 20% (77.8 ± 30.4 pg/ml vs. 42.6 ± 17.2 pg/ml, p = 0.12), but they were not significantly different from baseline. Resting anti-inflammatory levels of IL-4 and IL-10 decreased after training (31% and 17%, respectively), but were not statistically significant (p>0.05). CONCLUSIONS: Eight weeks of resistance training may influence resting levels of both pro- and anti-inflammatory cytokines in individuals with MS. The impact of exercise-induced cytokine changes on MS disease progression remains unclear and warrants further investigation. Supported by the National Multiple Sclerosis Society

Cytokine Levels After Eight Weeks of Progressive Resistance Training in Multiple Sclerosis Patients

Cytokine Levels After Eight Weeks of Progressive Resistance Training in Multiple Sclerosis Patients

Cardiovascular Risk Modification After Resistance Training in Subjects with Multiple Sclerosis

2095 Multiple sclerosis (MS) is an inflammatory autoimmune disease characterized by central nervous system demyelination. Individuals with MS are predisposed to reduced levels of voluntary physical activity, hastening the development of cardiovascular disease, thereby warranting early detection and intervention strategies. Recently, C-reactive protein (CRP) has been used as a biomarker for cardiovascular risk with levels of greater than 3 mg/L reflective of high risk. PURPOSE: To determine whether progressive lower body resistance training would alter cardiovascular risk biomarkers in overweight MS patients. METHODS: Six relapsing remitting MS patients (age: 47.3 ± 4.7, mean ± SE) with self-reported Expanded Disability Status Scores (EDSS) ranging from (1.5–5.5) completed twice weekly resistance training sessions for eight consecutive weeks. Fasting blood samples were obtained by venipuncture before and after the strength training intervention. Pre-post tests were computed using a paired t-test. RESULTS: Significant reductions in CRP were observed (4.94 ± 0.58 vs. 3.58 ± 0.38 mg/L, p<0.01) after 8 weeks of resistance training. However, total cholesterol (173 ± 11.3 vs. 160.1 ± 9.1 mg/dL, p = 0.07), and high-density lipoproteins remained unchanged as a result of training (46.0 ± 2.8 vs. 46.6 ± 3.6 mg/dL, p>0.05). Interleukin-6 levels tended to decrease from pre-training (5.06 ± 1.3 pg/mL) vs. post-training (3.72 ± 0.82 pg/mL, p = 0.07). Body mass index (BMI) decreased significantly from pre-training (28.27 ± 2.8) vs. post training (27.9 ± 2.8 kg/m2, p = 0.04). CONCLUSIONS: Eight weeks of progressive resistance training lowers levels of CRP (28%), self reported EDSS score (16.9%), and BMI (1.3%) and may contribute to cardiovascular risk reduction MS patients. Further studies with larger sample sizes are warranted. Supported by the National Multiple Sclerosis Society

Maintenance of whole muscle strength and size following resistance training in older men.

Following a progressive resistance training (PRT) program of 3 days per week, we sought to examine how effective a resistance training maintenance program of 1 day per week would be to preserve muscle strength and size in older men. Each subject's whole muscle strength (1 repetition maximum, or 1RM) and whole muscle size (determined by computed tomography scan) were measured before (T1) and after (T2) 12 weeks of PRT and again following 6 months (T3) of training (TR) or detraining (DT). During the 12-week PRT, older men (N = 10; age 70 +/- 4 years) trained their knee extensors 3 days per week at 80% of their 1RM. The maintenance program consisted of older men (n = 5; TR; 75 +/- 1 years) who completed 3 sets of 10 repetitions at 80% of their 1RM 1 day per week (this was equivalent to a single training session that was performed 3 days per week during the 12-week PRT). The other group of older men (n = 5; DT; 69 +/- 1 years) resumed their normal lifestyle (no regular physical activity) following the 12-week PRT. From T1 to T2, muscle strength increased (p <.05) 45% (66 +/- 10 to 94 +/- 10 kg) in the TR group and 53% (50 +/- 6 to 74 +/- 7 kg) in the DT group. From T2 to T3, whole muscle strength of the TR group was unchanged (96 +/- 11 kg), whereas strength decreased (p <.05) in the DT group by 11% (66 +/- 6 kg). Muscle size demonstrated a similar pattern with a 7% increase (p <.05) in both groups from T1 to T2. No change in muscle size was found in the TR group from T2 to T3, whereas the DT group had a 5% reduction (p <.05). These data indicate that resistance training 1 day per week was sufficient to maintain muscle strength and size in these older men following a 12-week PRT program. Furthermore, the men who resumed their normal lifestyle (no regular physical activity) experienced significant losses in muscle strength and size.

IMPACT OF HIGH VELOCITY POWER TRAINING ON STRENGTH &amp; POWER IN OLDER WOMEN

Peak power declines more precipitously than strength with age and is a reliable measure of impairment and a strong physiologic predictor of functional performance in advancing age. yet no published studies have demonstrated the reversibility of low muscle power in the elderly. Therefore, we conducted a randomized trial comparing standard slow velocity progressive resistance training (PRT) to high velocity power training (HVPT) in older women with self-reported disability. Thirty women (73 ± 1 yrs, 68.4 ± 9.5 kg, BMI = 30.1 ± 1.1) were randomized into 16 weeks of PRT, or HVPT. Training was performed 3 times per wk. and subjects completed 3 sets (8–10 reps.) of knee extension (KE) and leg extension (LE) exercises at 70% of the 1 RM. LE training force and total work was similar between groups (p > 0.05). However, HVPT generated significantly higher power during training sessions compared to PRT (442 W vs. 108 W, p < 0.001). Although LE 1 RM muscle strength increased (P < 0.001) similarly in both groups as a result of the training, peak power increased significntly more in HVPT than in PRT (3.582 W/kg vs. 1.857 W/kg, p < 0.001). Furthermore, HVPT at 70% of the 1 RM reslted in a significantly greater improvement in LE baseline peak power at 40, 50, 60, 75, 80, 85, and 90% of the 1 RM compared to PRT (p < .05). The improved LE peak power spanning a wide range of external resistances suggests that HVPT may have a more advantageous influence on strength, power, and function compared to more traditional PRT in the elderly.

Progressive resistance training in neuromuscular patients. Effects on force and surface EMG

In a randomized clinical trial the efficacy of strength training was studied in patients with myotonic dystrophy ( n=33) and in patients with Charcot-Marie-Tooth disease ( n=29). Measurements were performed at the start and after 8, 16 and 24 weeks of progressive resistance training. Surface electromyography (SEMG) of proximal leg muscles was recorded during isometric knee extension at maximum voluntary contraction (MVC) and at 20, 40, 60 and 80% of MVC. Changes in MVC, maximum electrical activity and torque–EMG ratios (TER) were calculated. Fatigue was studied by determining the changes in endurance and in the decline of the median frequency ( F med) of the SEMG during a sustained contraction at 80% MVC. These parameters showed no significant changes after the training in either of the diagnostic groups. Only the Charcot-Marie-Tooth training group showed a gradual significant increase in mean MVC over the whole training period (21%). After 24 weeks, the increase in mean RMS was similar (25%), but this was mainly due to a sharp rise during the first 8 weeks of training (20%). The findings indicate that the initial strength increase was due to a neural factor, while the subsequent increase was mainly due to muscle hypertrophy.

Changes in power with resistance training in older and younger men and women.

Muscle power diminishes with increasing age and inactivity. The capacity for older adults to increase muscle power with resistance exercise has not been examined; therefore, we examined the influence of progressive resistance training (PRT) on muscle power output in 17 men and women aged 56-66 years, and compared their responses to 15 men and women aged 21-30 years. All subjects performed 12 weeks of PRT at a workload equivalent to 80% of the one repetition maximum (1RM). All training and assessments of 1RM and power were made on Keiser pneumatic resistance machines. Subjects performed five exercises, three sets per exercise, twice weekly. Muscle power was measured (isotonically) at resistances equivalent to 40, 60, and 80% of the 1RM, on the knee extension and arm pull machines. All subjects increased arm pull power similarly at 40 and 60% of 1RM, independent of age or sex. There was not a significant increase in arm pull power at 80% of 1RM. Older and younger subjects also had similar absolute increases in leg extensor power at 40 and 60% of 1RM, but men responded with greater absolute gains than women at these percentages (p < .05). The increase in leg extensor power at 80% of 1RM was similar in all groups. Older and younger subjects increased strength similarly in all exercises except the left knee extension. Independent of age, men increased strength more than women in all exercises except the double leg press. These data demonstrate that individuals in their sixth decade can still improve muscle power (and strength); however, men may realize greater absolute gains than women.

FEASIBILITY OF INCREASING LEAN BODY MASS IN HIV-INFECTED ADULTS USING PROGRESSIVE RESISTANCE TRAINING.

1041 Wasting is a major cause of disability and mortality in HIV infection. Treatments for wasting include growth hormone and testosterone therapy, but these are expensive and have potentially severe side effects. We examined the capacity of progressive resistance training (PRT) to increase lean body mass(LBM) in adults with HIV infection. Eighteen adults with HIV infection (14 M, 4 F; 9 African-American, 8 Caucasian, 1 Native-American; mean age 41, range 32-47; mean CD4 count 202 mm-3, mean BMI 24.6 kg/m2.; risk factors for HIV: IVDU 9, MSM 8, Unknown 1) completed 8 weeks of PRT using compressed air resistance equipment (Keiser Co., Fresno, CA). Subjects trained three times per week at 80% of 1-repetition maximum, performing 3 sets of 8 repetitions/machine. Body composition was measured by dual-energy x-ray absorptiometry (DXA; Hologic QDR 2000). After 8 weeks of PRT, mean strength(summed over leg extension, leg press, chest press, and lateral pull) increased by (mean ± SD) 50.7 ± 12.1%. There was an increase in body weight of 1.0 ± 2.7 kg (p < 0.2). LBM increased by 1.7 ± 1.9 kg (p < 0.004), while body fat declined by 0.7 ± 2.7 kg (p < 0.3). These data indicate that LBM can be increased in HIV (+) adults using a short-term, high-intensity PRT program.

STRENGTH AND POWER CHANGES FOLLOWING RESISTANCE TRAINING IN OLDER AND YOUNGER WOMEN 435

It has been shown that older individuals can improve or maintain muscular strength and power by resistance training; however, it is unclear how the magnitude of their responses to resistance training compare to those of younger individuals. Therefore, we measured upper and lower body strength (one repetition maximum (1RM)) and power in eight older women (OW, 60.4 ± 1.3 yrs) and nine younger women (YW, 25.9 ± 1.2 yrs) before and after 12 weeks of progressive resistance training (RT; 2 d/wk, 3 sets/exercise/d) performed at 80% of the 1RM. Fat-free mass was similar (43.1 ±2 vs. 43.1 ±1 kg) in OW and YW. All RT, 1RM and power measurements were made on Keiser pneumatic resistance equipment. Below are the changes (mean ± SE) in 1RM and power at 80% of 1RM in two muscle groups after 12 weeks of RT:Table Regardless of age, all of the women (n=17) increased upper and lower body strength and power with RT (p<0.05). Increases in left knee extensor strength, upper body strength, and upper and lower body power were similar between OW and YW; however, OW increased right knee extensor strength less than YW. These data demonstrate that older and younger women have a similar capacity for improving upper and lower body muscular strength and power.