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Background : Previous investigators have reported that long term eccentric cycling increases muscle size and strength in a variety of populations. The joint-specific strategies used to absorb power during eccentric cycling, however, have not been identified. The purpose of this investigation was to determine the extent to which ankle, knee, and hip joint actions absorb power during eccentric cycling. Methods : Eight active males resisted the reverse moving pedals of an isokinetic eccentric ergometer (60rpm) while targeting 20% of their maximum concentric cycling power. Pedal reaction forces and joint kinematics were recorded with an instrumented pedal and instrumented spatial linkage system, respectively. Joint powers were calculated using inverse dynamics; averaged over complete crank revolutions and over extension and flexion phases; and differences were assessed with a one-way ANOVA. Findings : Ankle, knee, and hip joint actions absorbed 10 (SD 3)%, 58 (SD 8)%, and 29 (SD 9)% of the total power, respectively, with 3 (SD 1)% transferred across the hip. The main power absorbing actions were eccentric knee extension (−139 (SD 21) watts), eccentric hip extension (−51 (SD 31) watts), and eccentric hip flexion (−25 (SD 6) watts). Interpretation : Eccentric cycling was performed with a combination of knee and hip joint actions which is consistent with submaximal concentric cycling. These data support and extend previous work that eccentric cycling improves knee extensor function and hip extensor muscle cross sectional area. Such information may allow clinicians to take even greater advantage of eccentric cycling as a rehabilitation modality. [Copyright &y& Elsevier]

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]

Isometric strength loss following damaging eccentric exercise (Edam) has been widely studied but changes in functional (maximal power, Pmax) and perceptual (rating of perceived exertion, RPE) responses have received less attention. Our objective was to establish the time course of alterations in Pmax and RPE following Edam. Eight trained cyclists performed 5 minutes of eccentric cycling with their right leg (damage) and concentric cycling with their left leg (control). Single-leg Pmax was assessed with inertial load cycling. RPE in response to a standard submaximal cycling task was assessed with a Borg scale. Measures were assessed at 7 time points (pre, 0, 24, 48, 72, 96, 120 hrs post). Repeated measures ANOVA indicated a significant main effect for time. Pmax decreased (0-72 hrs post) and RPE increased (0-96 hrs post) in the damaged leg (p<0.05). In two cyclists, we also examined power produced at the ankle, knee, and hip. We observed that knee power decreased by 177 watts whereas hip power increased by 111 watts at 120 hrs post (preliminary data). Thus, although Pmax and RPE recovered, that recovery was partially due to compensation by other less damaged muscles. [ABSTRACT FROM AUTHOR]

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]

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]

Previous investigators have reported velocity-dependent strength loss for single-joint actions following acute eccentric exercise. The extent to which velocity influences recovery of multi-joint function is not well documented. Our main purpose was to compare alterations in maximal cycling power produced across a range of pedaling rates following eccentric exercise. An additional purpose was to determine the extent to which changes in rating of perceived exertion (RPE) associated with submaximal cycling reflect changes in maximal cycling power. Eighteen cyclists performed baseline trials of maximal and submaximal single-leg concentric cycling immediately before and 24 and 48 h after acute submaximal single-leg eccentric (151 ± 32 W, 487 ± 107 s) and concentric (148 ± 21 W, 488 ± 79 s) cycling trials. Maximum cycling power (apex of power-pedaling rate relationship; P (max)) was assessed using inertial-load cycling, and powers produced at 65, 110 and 155 rpm were also analyzed. Compared to baseline, P (max) was reduced (11-13%) at 24-48 h in the eccentric leg (P < 0.001). Power produced at 65, 110 and 155 rpm was reduced by similar relative magnitudes (11-15%) at 24-48 h in the eccentric leg. RPE increased (15-18%) at 24-48 h in the eccentric leg (P < 0.001). Magnitudes of relative changes in RPE did not differ from those for P (max). There were no alterations in the concentric leg. Our results indicated a global, rather than velocity-specific, reduction in neuromuscular function. Such a global reduction does not support the notion of fiber-type specific damage from eccentric exercise. The similar relative changes in RPE and P (max) suggest that increased exertion may reflect the need to recruit additional motor units to produce the same submaximal power. [ABSTRACT FROM AUTHOR]