Reactive knee stiffness strategies between various conditioning histories
| Author(s) | Oates, David Craig, II | |
| Date Accessioned | 2015-08-19T12:03:28Z | |
| Date Available | 2015-08-19T12:03:28Z | |
| Publication Date | 2014 | |
| Abstract | Context: Optimizing joint stiffness through appropriate muscular activation is crucial for maintaining stability and preventing injury. Various conditioning techniques may serve to affect joint stability through mechanisms that may increase joint stiffness, or improve the ability to absorb loads. Understanding the strategies that individuals with varying conditioning histories regulate knee stiffness would be crucial for optimizing joint stability and preventing injury. Objective: To assess if knee stiffness strategies differ in various conditioning histories. Patients or Other Participants: 15 endurance (19.8±1.1 yrs, 65.9±8.8 kg, 176.6±8.6 cm), 12 power (20.3±1.3 yrs, 74.5±10.3 kg, 175.5±4.9 cm), and 15 control subjects (20.1±1.6 yrs, 79.0±12.8 kg, 177.0±4.3 cm). Interventions: Participants sat on a custom stiffness device that generated a 40° flexion perturbation to the knee and were instructed to maintain muscle contraction or relaxation, resist the perturbation, or reactively relax. Muscle activation was recorded through electromyography from quadriceps and hamstring muscles. Main Outcome Measures: Stiffness values (Nm/deg/kg) at short range (0-4°) and long range (0-40°), muscle activation amplitude (%MVIC) and timing (ms). Results: Passive short-range stiffness was greater in endurance athletes (0.057±0.012 nm/°/kg) than control group (0.047±0.008 nm/°/kg, p=0.021); while passive long-range stiffness was greater in power athletes (0.0020±0.001 nm/°/kg) than endurance athletes (0.0016±0.001 nm/°/kg, p=0.016). Active-reactive long-range stiffness was greater in endurance athletes (0.051±0.017 nm/°/kg) than control (0.033±0.011 nm/°/kg, p=0.001) and power (0.037±0.015 nm/°/kg, p=0.044) groups. Endurance athletes also displayed greater peak EMG in quadriceps during passive condition (p < 0.050) than power and controls. The endurance group had increased EMG area under the curve (AUC) for quadriceps than power and control groups during PRE time period (p < 0.050) for passive reactive condition. Conclusions: These findings indicate a power-based training history may help increase passive joint stiffness, while endurance-based training can improve reactive muscular characteristics. Both training groups displayed alterations in preparatory and reactive muscle activation and stiffness regulation, with either improving knee joint stability and preventing injuries. However, in cases of patients with increased laxity, endurance training may be beneficial to muscle tone and joint stiffness; conversely, power training may potentially facilitate the deactivation of certain muscles that negative affect joint stability. | en_US |
| Advisor | Swanik, Charles B. | |
| Degree | M.S. | |
| Department | University of Delaware, Department of Kinesiology and Applied Physiology | |
| Unique Identifier | 918940061 | |
| URL | http://udspace.udel.edu/handle/19716/16965 | |
| Publisher | University of Delaware | en_US |
| URI | http://search.proquest.com/docview/1665586042?accountid=10457 | |
| dc.subject.lcsh | Knee. | |
| dc.subject.lcsh | Knee -- Muscles. | |
| dc.subject.lcsh | Exercise. | |
| Title | Reactive knee stiffness strategies between various conditioning histories | en_US |
| Type | Thesis | en_US |