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Background and Purpose After total knee arthroplasty (TKA), persistent quadriceps muscle atrophy and weakness impairs physical function. Blood flow restriction (BFR) exercise is emerging as a potential method to improve muscle size and strength in clinical populations with orthopedic limitations. There are no randomized controlled studies documenting BFR exercise after TKA. This case report describes the use of home-based BFR exercise to increase quadriceps size, strength, and physical function after TKA. Case Description A 59-year-old man (6 months post-TKA) performed body weight and walking exercises with BFR 5×/wk for 8 weeks. Blood flow in the TKA leg was restricted using a thigh cuff inflated to 50% of limb occlusion pressure. Lean leg mass, vastus lateralis thickness, knee extensor strength, and physical function were measured at baseline (6 months post-TKA), posttraining (8 months post-TKA), and long-term follow-up (14 months post-TKA). Outcomes After training, lean leg mass, vastus lateralis thickness, and knee extensor strength in the TKA leg increased by 4%, 14%, and 55%, respectively. Compared with baseline, posttraining knee extensor strength symmetry (TKA/uninvolved leg) increased from 64% to 98%. The patient's performance improved for the 30-second chair stand, 40-m fast walk, and 6-minute walk tests. Increased quadriceps and physical function were maintained at the long-term follow-up. Discussion With enhanced quadriceps and physical function, the patient resumed independent physical activity. Muscle and strength gains surpassed those typically reported after TKA. Outcomes suggest that home-based BFR exercise was feasible, safe, and effective. BFR exercise after TKA is promising and warrants further research. [ABSTRACT FROM AUTHOR]

Quadriceps atrophy and weakness can persist for years after anterior cruciate ligament reconstruction (ACLR). We evaluated the effectiveness of a home-based blood flow restriction (BFR) exercise program to increase quadriceps size and strength several years after ACLR. Nine adults with ACLR (5±2 yrs post-surgery, ≤90% symmetry in quadriceps size and strength) and nine uninjured controls volunteered. ACLR participants exercised at home for 25 min, 5×/wk for 4 wks (single-leg knee extension, bodyweight half-squats, walking). Blood flow in only the involved leg was restricted using a thigh cuff inflated to 50% of limb occlusion pressure. Rectus femoris and vastus lateralis thickness and knee extensor strength were measured before and after training. Baseline and post-training symmetry (involved leg/uninvolved leg) indices were compared to uninjured controls. Rectus femoris and vastus lateralis thickness and knee extensor strength in the involved leg increased by 11±5%, 10±6%, and 20±14%, respectively (all P<0.01). Compared to baseline, post-training knee extensor strength symmetry increased from 88±4 to 99±5% (P<0.01) and did not differ from uninjured controls (99±5%, P=0.95). Implementation of BFR exercise at home was feasible, safe and effective. Results extend upon early post-operative application of BFR exercise for ACLR recovery and demonstrate that BFR can improve quadriceps function long after ACLR. [ABSTRACT FROM AUTHOR]

Introduction: Exercise with blood flow restriction (BFR) is emerging as an effective modality for improving muscular function in clinical and athletic populations. Selection of cuff pressure is critical because it should maximize metabolic stress without completely occluding blood flow or compromising user safety. It is unknown how cuff pressures determined at rest influence blood flow hemodynamics during exercise.Purpose: We evaluated changes in blood flow and tissue perfusion before, during, and after exercise with BFR.Methods: Ten males performed rhythmic handgrip exercise (30 contractions, 30% MVC) at 0%, 60%, 80%, 100%, and 120% of limb occlusion pressure (LOP). Brachial artery blood flow and tissue saturation were assessed using Doppler ultrasound and near-infrared spectroscopy, respectively.Results: At rest blood flow generally decreased with increased pressure (0% > 60% ≈ 80% > 100% ≈ 120% LOP). During 60% and 80% LOP conditions, blood flow increased during exercise from rest and decreased after exercise (all P < 0.05). Compared to 0% LOP, relative blood flow at 60% and 80% LOP decreased by 22-47% at rest, 22-48% during exercise, and 52-71% after exercise (all P < 0.05). Increased LOP decreased tissue saturation during exercise with BFR (P < 0.05). Heart rate, mean arterial pressure, and cardiac output did not differ across LOP.Conclusion: At pressures below LOP the cardiovascular system overcame the external pressure and increased blood flow to exercising muscles. Relative reductions in blood flow at rest were similar to those during exercise. Thus, the relative occlusion measured at rest approximated the degree of occlusion during exercise. Moderate cuff pressures increased metabolic stress without completely occluding blood flow. [ABSTRACT FROM AUTHOR]

We implemented a team-based activity in our exercise physiology teaching laboratory that was inspired from Abbott et al.'s classic 1952 Journal of Physiology paper titled "The physiological cost of negative work." Abbott et al. connected two bicycles via one chain. One person cycled forward (muscle shortening contractions, positive work) while the other resisted the reverse moving pedals (muscle lengthening contractions, negative work), and the cost of work was compared. This study was the first to link human whole body energetics with isolated muscle force-velocity characteristics. The laboratory activity for our students (n = 35) was designed to reenact Abbott et al.'s experiment, integrate previously learned techniques, and illustrate differences in physiological responses to muscle shortening and lengthening contractions. Students (11-12 students/laboratory section) were split into two teams (positive work vs. negative work). One student from each team volunteered to cycle against the other for ~10 min. The remaining students in each team were tasked with measuring: 1) O2 consumption, 2) heart rate, 3) blood lactate, and 4) perceived exertion. Students discovered that O2 consumption during negative work was about one-half that of positive work and all other physiological parameters were also substantially lower. Muscle lengthening contractions were discussed and applied to rehabilitation and sport training. The majority of students (>90%) agreed or strongly agreed that they stayed engaged during the activity and it improved their understanding of exercise physiology. All students recommended the activity be performed again. This activity was engaging, emphasized teamwork, yielded clear results, was well received, and preserved the history of classic physiological experiments. [ABSTRACT FROM AUTHOR]

During upper-body tasks, use of the lower body is important for minimizing physiological strain and maximizing performance. The lower body has an integral role during standing upper-body tasks, however, it is less clear if it is also important during seated upper-body tasks. We determined the extent to which the lower body influenced seated arm cranking performance. Eleven males performed incremental (40 + 20 W · 3 min-1) and short-duration maximal effort (5 s, 120 rpm) arm cranking trials with and without lower-body restriction. The lower body was restricted by securing the legs to the seat and suspending them off the floor. Upper-body peak oxygen consumption (VO2peak) and maximal power were determined. At the end of the incremental protocol, lower-body restriction reduced VO2peak by 14 ± 12 % (P < 0.01) compared to normal arm cranking. At greater submaximal stages (60-100 % isotime) heart rate, ventilation, RER, and arm-specific exertion increased to a greater extent (all P < 0.05) with lower-body restriction. During short duration maximal arm cranking, lower-body restriction decreased maximal power by 23 ± 9 % (P < 0.01). Results indicated that lower-body restriction limited aerobic capacity, increased physiological strain during high-intensity submaximal exercise, and compromised maximal power generating capacity. These results imply that use of the lower body is critical when performing seated arm cranking. Our findings have implications for exercise testing, training and rehabilitation. [ABSTRACT FROM AUTHOR]

Introduction: Eccentric leg cycling (cycle ergometry adapted to impose muscle lengthening contractions) offers an effective exercise for restoring lower-body muscular function, maintaining health, and improving performance in clinical and athletic populations.Purpose: We extended this model to the upper body and evaluated the effectiveness of a 7-week eccentric arm cycling (ECCarm) intervention to improve upper-body muscular function. We also explored whether ECCarm would alter arterial function.Methods: Participants performed ECCarm (n = 9) or concentric arm cycling (CONarm; n = 8) 3×/week while training intensity increased (5-20 min, 60-70% upper-body peak heart rate). Maximum elbow extensor strength, upper-body concentric power, and peripheral and central arterial stiffness were assessed before and after training.Results: During training, heart rates and perceived exertion did not differ between groups (~68% upper-body peak heart rate, ~12 Borg units, both P > 0.05), whereas power during ECCarm was ~2× that for CONarm (122 ± 43 vs. 59 ± 20 W, P < 0.01). Muscle soreness for ECCarm was greater than CONarm (P = 0.02), however, soreness was minimal for both groups (<0.50 cm). Following training, ECCarm exhibited greater changes in elbow extensor strength (16 ± 10 vs. 1 ± 9%, P = 0.01) and upper-body power (6 ± 8 vs. -3 ± 7%, P < 0.01) compared to CONarm. Peripheral and central arterial stiffness did not change for either group (both P > 0.05).Conclusion: Upper-body eccentric exercise improved dynamic muscular function while training at low exertion levels. Results occurred with minimal soreness and without compromising arterial function. ECCarm findings parallel eccentric leg cycling findings and indicate that eccentric cycle ergometry offers a robust model for enhancing upper-body muscular function. ECCarm could have applications in rehabilitation and sport training. [ABSTRACT FROM AUTHOR]

Introduction: Blood flow restriction (BFR) exercise has emerged as a method of increasing muscle size and strength with low intensity resistance training. While the cuff pressures used during BFR are typically a percentage of resting arterial occlusion pressure (AOP), the impact these cuff pressures have on blood flow during lower body exercise is unknown.Purpose: To determine how various cuff pressures impact blood flow and tissue perfusion during exercise.Methods: Eleven healthy male participants completed four sets of knee extension (30 reps per set at 30% max torque) with 0%, 60%, 80%, and 100% of arterial occlusion pressure (AOP) was applied to the proximal portion of the thigh. Femoral artery blood flow, tissue oxygenation, and central hemodynamics were continuously recorded before, during, and after exercise. Electromyography (EMG) amplitude was recorded from the vastus lateralis during exercise.Results: Blood flow increased during exercise compared to rest across all cuff pressures (p < 0.001), however compared to 0%, the absolute blood flow was reduced by 34 ± 17%, 45 ± 22%, and 72 ± 19% for 60, 80, and 100% AOP, respectively. Furthermore, each cuff pressure resulted in similar relative changes in blood flow before, during, and after exercise. During exercise, tissue saturation index (TSI) decreased as cuff pressure increased (p ≤ 0.005) with the exception of 80 to 100% AOP. Deoxyhemoglobin increased (p ≤ 0.001) with cuff pressure.Conclusion: Our data indicate that while BFR knee extension elicits an absolute hyperemic response at cuff pressures up to 100% resting AOP, the relative reductions in blood flow are consistent across rest, exercise and recovery. [ABSTRACT FROM AUTHOR]