Context Researchers have traditionally used motion capture to quantify discrete data points (peak values) during hop testing. However, these analyses restrict the evaluation to a single time point (ie, certain percentage of stance) and provide only a narrow view of movement. Applying more comprehensive analyses may help investigators identify important characteristics that are masked by discrete analyses often used to screen patients for activity. Objective To examine the utility of functional data analyses to reveal asymmetries that are undetectable using discrete (ie, single time point) evaluations in participants with a history of anterior cruciate ligament reconstruction (ACLR) who achieved clinical hop symmetry. Design Cross-sectional study. Setting Laboratory. Patients or Other Participants Fifteen participants with unilateral ACLR (age = 21 ± 3 years, time from surgery = 4 ± 3 years) and 15 control participants without ACLR (age = 23 ± 2 years). Intervention(s) Lower extremity biomechanics during the triple–hop-for-distance task for the ACLR and contralateral limbs of patients and a representative limb of control participants were measured. Main Outcome Measure(s) Peak sagittal-plane joint power, joint work, and power profiles were determined. Results Using discrete analyses, we identified lower peak knee power and work in the ACLR limb compared with the contralateral and control limbs ( P < .05) but were unable to demonstrate differences at the ankle or hip. Using functional data analyses, we observed asymmetries at the ankle, knee, and hip between the ACLR and contralateral or control limbs throughout stance ( P < .05), and it was revealed that these asymmetries stemmed from knee power deficits that were prominent during early loading. Conclusions Despite achieving hop-distance symmetry, the ACLR knees absorbed less power. Although this information was revealed using discrete analyses, underlying asymmetries at the ankle and hip were masked. Using functional data analyses, we found interlimb asymmetries at the ankle, knee, and hip. Importantly, we found that functional data analyses more fully elucidated the extent and source of asymmetries, which can be used by clinicians and researchers alike to aid in clinical decision making.

Context Researchers have traditionally used motion capture to quantify discrete biomechanical data points (peak values) during hop testing. However, these analyses provide a narrow view of movement as they restrict the evaluation to a single time point (i.e. certain percentage of stance). The application of more comprehensive analyses may identify important characteristics that are masked by discrete analyses often used to screen patients for activity. Objective To examine the utility of functional data analyses to reveal asymmetries that are undetectable by discrete (i.e. single time point) evaluations in those with a history of anterior cruciate ligament reconstruction (ACLR) who achieve clinical hop symmetry. Design Cross- sectional study. Setting Laboratory. Patients or Other Participants 15 subjects with unilateral ACLR (age=21±3yrs; time from surgery= 4±3yrs) and 15 healthy controls (age=23±2yrs) participated. Intervention(s) Lower extremity biomechanics were collected during the triple hop for distance task. Main Outcome Measure(s) Peak sagittal plane joint power, joint work, and power profiles were determined. Results Discrete analyses identified significantly lower peak knee power and work in the ACLR limb compared to contralateral and control limbs (p<0.05), but were unable to identify differences at the ankle or hip. Functional data analyses identified significant asymmetries at the ankle, knee, and hip between ACLR and contralateral or control limbs throughout stance (p<0.05) and revealed that these asymmetries stemmed from knee power deficits that were prominent during early loading. Conclusions Despite achieving hop distance symmetry, ACLR knees absorbed less power. While this information was revealed with the discrete (i.e. single time point) analyses, underlying asymmetries at the ankle and hip were masked. Functional data analyses identified inter-limb asymmetries at the ankle, knee, and hip throughout ground contact and more fully elucidate the extent and source of asymmetries that can be utilized by clinicians and researchers alike to guide clinical decision making.

Context Long-term eccentric exercise is known to promote muscle growth better than concentric exercise, but its acute effect on muscle is not well understood because of misinterpreted modeling and in situ and in vitro stretch protocols. Knowing if the initial bout of eccentric exercise promotes muscle growth and limits damage is critical to understanding the effect of this mode of exercise. Objective To directly evaluate the immediate effects of eccentric and concentric exercises on untrained muscle when fiber strains were physiological and exercise doses were comparable. Design Controlled laboratory study. Setting Laboratory. Patients or Other Participants A total of 40 skeletally mature male Long-Evans rats (age = 16 weeks, mass = 452.1 ± 35.2 g) were randomly assigned to an eccentric exercise (downhill walking, n = 16), concentric exercise (uphill walking, n = 16), or control (no exercise, n = 8) group. Intervention(s) Rats were exposed to a single 15-minute bout of eccentric or concentric exercise on a motorized treadmill and then were euthanized at 6 or 24 hours postexercise. We harvested the vastus lateralis muscle bilaterally. Main Outcome Measure(s) The percentage increase or decrease in protein abundance in exercised animals relative to that in unexercised control animals was evaluated as elevated phosphorylated p70 S6k relative to total p70 S6k . Fiber damage was quantified using immunoglobulin G permeability staining. One-way analysis of variance and post hoc Tukey tests were performed. Results Rats exposed to eccentric exercise and euthanized at 24 hours had higher percentage response protein synthesis rates than rats exposed to eccentric exercise and euthanized at 6 hours ( P = .02) or to concentric exercise and euthanized at 6 ( P = .03) or 24 ( P = .03) hours. We assessed 9446 fibers for damage and found only 1 fiber was infiltrated (in the concentric exercise group euthanized at 6 hours). Furthermore, no between-groups differences in immunoglobulin G fluorescent intensity were detected ( P = .94). Conclusions Incorporating eccentric exercise is a simple, universally available therapeutic intervention for promoting muscle recovery. A single 15-minute dose of eccentric exercise to a novice muscle can better exert an anabolic effect than a comparable dose of concentric exercise, with very limited evidence of fiber damage.