Subject factors influencing blood flow restriction in the arm at low cuff pressures.

BACKGROUND: Limb circumference predicts the pressure needed for complete occlusion. However, that relationship is inconsistent at moderate pressures typical of effective blood flow restriction (BFR) training. The purpose of this study was to investigate the influence of subject factors on BFR at low restriction pressures in the arm. METHODS: Fifty subjects had arm anthropometrics assessed by peripheral quantitative computed tomography (pQCT), sum of skinfold thickness (sumSKF) and Gulick tape (Gulick tape circumference [Gulick Circ.]) at cuff level. Blood flow (BF) was measured with ultrasound at baseline and five restrictive pressures (20, 30, 40, 50 and 60 mmHg). Relationships between subject characteristics and BFR were assessed using Pearson's correlations and hierarchical regression. RESULTS: BF decreased (p < 0.05) at each incremental pressure. Regression models including percent muscle composition (%Muscle), pQCT circumference and systolic blood pressure (SBP), were significant at all five pressures (R2 = 0.18-0.49). %Muscle explained the most variance at each pressure. Regression models including sumSKF, Gulick Circ. and SBP, were significant at 30-60 mmHg (R2 = 0.28-0.49). SumSKF explained the most variance at each pressure. CONCLUSIONS: At low pressures (20-60 mmHg), there is considerable variability in the magnitude of BFR across individuals. Arm composition factors (muscle and fat) explained the greatest variance at each cuff pressure and may be the most important consideration when using BFR protocols.

Blood Flow Restriction Training: Implementation into Clinical Practice.

To improve muscular strength and hypertrophy the American College of Sports Medicine recommends moderate to high load resistance training. However, use of moderate to high loads are often not feasible in clinical populations. Therefore, the emergence of low load (LL) blood flow restriction (BFR) training as a rehabilitation tool for clinical populations is becoming popular. Although the majority of research on LL-BFR training has examined healthy populations, clinical applications are emerging. Overall, it appears BFR training is a safe and effective tool for rehabilitation. However, additional research is needed prior to widespread application.

Efficacy of Blood Flow-Restricted Low-Load Resistance Training For Quadriceps Strengthening in Men at Risk of Symptomatic Knee Osteoarthritis.

BACKGROUND: Greater quadriceps strength has been associated with lower risk of symptomatic knee osteoarthritis (OA) in older adults. However, factors that confer elevated risk of knee OA (eg, sedentary lifestyle, obesity, and knee injury) also contribute to a reduced tolerance of resistance training programs at ≥60% 1-repetition maximum (1RM). Therefore, the current study assessed whether concurrent application of blood flow restriction (BFR) to low-load resistance training is an efficacious and tolerable means of improving quadriceps strength in men at risk of symptomatic knee OA. METHODS: Men older than age 45, with a history of knee injury or elevated body mass index (BMI), were randomized to low-load resistance training (30% 1RM) either with or without concurrent BFR. Isotonic double-leg press strength and isokinetic knee extensor strength were assessed before and after 4 weeks of training 3 times/wk. Knee pain (Knee Osteoarthritis Outcome Score) was assessed for tolerance. RESULTS: Of the 42 men (mean age 56.1 ± 7.7 years) who were randomized, 41 completed the program. There were no significant intergroup differences in age, BMI, knee pathology, or muscle strength at baseline. Although leg press 1RM improved in both control and BFR groups, there were no significant intergroup differences in primary or secondary measures of muscle strength. The BFR was not associated with worsening of knee pain, but there was a significant improvement in knee pain in the control group. CONCLUSIONS: In comparison with training without BFR, addition of BFR to 30% 1RM resistance training for 4 weeks did not confer significantly greater increases in leg press or quadriceps strength in older men with risk factors for symptomatic knee OA.

Efficacy of blood flow-restricted, low-load resistance training in women with risk factors for symptomatic knee osteoarthritis.

OBJECTIVE: To assess whether concurrent blood flow restriction (BFR) during low-load resistance training is an efficacious and tolerable means of improving quadriceps strength and volume in women with risk factors for symptomatic knee osteoarthritis (OA). DESIGN: Randomized, double-blinded, controlled trial. SETTING: Exercise training clinical research laboratory. PARTICIPANTS: Women over age 45 years with risk factors for symptomatic knee OA. METHODS: Participants were randomized to either low-load resistance training (30% 1RM) alone (control) or with concurrent BFR and completed 4 weeks of 3 times per week leg-press resistance training. Those randomized to BFR wore a cuff that progressively restricted femoral blood flow over the weeks of training. Intergroup differences in outcome measures were compared using regression methods, while adjusting for BMI. MAIN OUTCOME MEASURES: Isotonic bilateral leg press strength, isokinetic knee extensor strength, and quadriceps volume by magnetic resonance imaging were assessed before and after participation. Secondary measures included lower limb muscle power (leg press and stair climb). Knee pain was assessed to determine tolerance. RESULTS: Of 45 women who consented to study participation, 40 completed the program. There were no significant intergroup differences in baseline characteristics except that body mass index was lower in the BFR group (P = .0223). Isotonic 1RM improved significantly more in the BFR group (28.3 ± 4.8 kg) than in the control group (15.6 ± 4.5 kg) (P = .0385). Isokinetic knee extensor strength scaled to body mass increased significantly more in the BFR group (0.07 ± 0.03 nm/kg) than in the control group (-0.05 ± 0.03 nm/kg) (P = .0048). Changes in quadriceps volume, leg press power, and knee-related pain did not significantly differ between groups. CONCLUSIONS: Addition of BFR to a 30% 1RM resistance training program was effective in increasing leg press and knee extensor strength in women at risk for knee OA, in comparison with the same program without BFR.

Effects of quadriceps and hamstrings proprioceptive neuromuscular facilitation stretching on knee movement sensation.

Stretching before competition has traditionally been thought to benefit performance; however, recent evidence demonstrating reduced muscle force and power immediately after stretching suggests otherwise. We hypothesized that knee joint position sense would be diminished immediately after proprioceptive neuromuscular facilitation (PNF) stretching to the hamstrings and quadriceps. Eighteen subjects (aged 18-30 years) were seated with their dominant foot attached to a motorized arm with the knee flexed at 135 degrees . To block external cues, the subjects wore a blindfold, earplugs, and headphones providing white noise. The knee was displaced in either the flexion or the extension direction at a velocity of 0.4 degrees .s, and subjects pressed a button when they sensed motion. The knee was returned to 135 degrees , and the test was repeated for a total of 10 trials. The PNF group received PNF stretching to the hamstrings and quadriceps of the dominant leg. The SHAM group had the dominant leg passively moved within each subject's functional range of motion. The ability to detect knee movement was retested in the PNF and SHAM groups. Pre- and posttest latencies between movement onset and subject response were analyzed. Results indicated that the PNF group had significantly increased latencies after stretching (from 2.56 +/- 0.83 to 3.46 +/- 1.90 seconds) compared with the SHAM group (3.93 +/- 2.40 to 3.72 +/- 2.15 seconds). It is concluded that PNF stretching of the hamstrings and quadriceps may acutely diminish sensitivity to knee movement. For coaches and trainers, these findings are consistent with previous reports of loss in muscle force and power immediately after stretching, suggesting that stretching just before competition may diminish performance.

Effects of strength training on the incidence and progression of knee osteoarthritis.

OBJECTIVE: Quadriceps weakness is a risk factor for incident knee osteoarthritis (OA). We describe a randomized controlled trial of effects of lower-extremity strength training on incidence and progression of knee OA. METHODS: A total of 221 older adults (mean age 69 years) were stratified by sex, presence of radiographic knee OA, and severity of knee pain, and were randomized to strength training (ST) or range-of-motion (ROM) exercises. Subjects exercised 3 times per week (twice at a fitness facility, once at home) for 12 weeks, followed by transition to home-based exercise after 12 months. Assessments of isokinetic lower-extremity strength and highly standardized knee radiographs were obtained at baseline and 30 months. RESULTS: Subjects in both groups lost lower-extremity strength over 30 months; however, the rate of loss was slower with ST than with ROM. Compared with ROM, ST decreased the mean rate of joint space narrowing (JSN) in osteoarthritic knees by 26% (P = not significant). However, the difference between ST and ROM groups with respect to frequency of knee OA progression in JSN consensus ratings was marginally significant (18% versus 28%; P = 0.094). In knees that were radiographically normal at baseline, JSN >0.50 mm was more common in ST than in ROM (34% versus 19%; P = 0.038). Incident JSN was unrelated to exercise adherence or changes in quadriceps strength or knee pain. CONCLUSION: The ST group retained more strength and exhibited less frequent progressive JSN over 30 months than the ROM group. The increase in incident JSN >0.50 mm in ST is unexplained and requires confirmation.

Motivational factors influencing older adults diagnosed with knee osteoarthritis to join and maintain an exercise program.

In order to provide successful interventions to increase physical activity among inactive older adults, it is imperative to understand motivational factors influencing exercise. The authors present data from 191 (baseline) and 125 (12-month) community-dwelling men and women with mean ages of 68.71 (7.47) and 67.55 (7.55) years, respectively, from a strength-training trial. Approximately 53% had diagnosed knee osteoarthritis. Using a Likert scale, participants self-reported their degree of motivation from personal, social, and environmental factors. Using multivariate analyses, the authors evaluated demographic and clinical correlates of motivational factors to join and continue with exercise. The following results were reported: Knee osteoarthritis was positively related to motivation from an organized exercise opportunity and from efficacy/outcome expectations, and knee pain was positively related to motivation from social support and experience with the exercise task. Understanding these motivators might help in targeting recruitment efforts and interventions designed to increase physical activity in older adults with lower extremity arthritis.

Acute effects of The Stick on strength, power, and flexibility.

The Stick is a muscle massage device used by athletes, particularly track athletes, to improve performance. The purpose of this project was to assess the acute effects of The Stick on muscle strength, power, and flexibility. Thirty collegiate athletes consented to participate in a 4-week, double-blind study, which consisted of 4 testing sessions (1 familiarization and 3 data collection) scheduled 1 week apart. During each testing session subjects performed 4 measures in the following sequence: hamstring flexibility, vertical jump, flying-start 20-yard dash, and isokinetic knee extension at 90 degrees x s(-1). Two minutes of randomly assigned intervention treatment (visualization [control], mock insensible electrical stimulation [placebo], or massage using The Stick [experimental]) was performed immediately prior to each performance measure. Statistical analyses involved single-factor repeated measures analysis of variance (ANOVA) with Fisher's Least Significant Difference post-hoc test. None of the variables measured showed an acute improvement (p < or = 0.05) immediately following treatment with The Stick.