Multiple Strength Assessments to Evaluate Adaptations to High-Load and Low-Load Blood Flow Restricted Exercise

Abstract

Differences in muscle strength adaptations between high-load (HL) and low-load blood flow restricted (BFR) resistance training protocols may be due to the type of strength test performed (e.g isotonic, isokinetic and isometric). PURPOSE: To assess differences in isotonic, isometric and isokinetic strength adaptations in older adults following HL and BFR resistance training. METHODS: Thirty-six males and females (mean: 75.6+7.6 years, 1.67+.09 m, 74.3+13.2 kg) classified as being at risk of mobility limitations were randomly assigned to HL (70% 1-RM) or low-load BFR (30% 1-RM coupled with a vascular restriction) exercise for the knee extensors twice per week for 6 weeks. A control group performed light upper body resistance and flexibility training. Knee extension 10-RM to predict 1-RM strength, isometric maximum voluntary contraction (MVC) and isokinetic strength at 60[BULLET OPERATOR]s-1, 180[BULLET OPERATOR]s-1, and 300[BULLET OPERATOR]s-1were measured before and after 6-weeks of training. RESULTS: HL and BFR training increased predicted 1-RM strength 34% (P<.001) and 24% (P<.001) respectively, from baseline to 6-weeks of training. HL training produced a 16% increase in MVC (P=.002) while BFR training did not change (P=.91). No interventions, included the control, resulted in changes in isokinetic strength at the various speeds (P>.20). CONCLUSION: Strength improvements from HL resistance training carried over to other strength tests. This favorable adaptation did not occur following BFR exercise which may limit the effectiveness of this training program. Isotonic training does not carry over to isokinetic strength adaptations and therefore may be a drawback when implementing resistance training programs for older adults. Supported by NIH grant 1R15 A6040700-01A1.