Prithvi Shah

Lower extremity skeletal muscle function in persons with incomplete spinal cord injury

Study design:A cross-sectional study design.Objectives:To characterize and specifically quantify impairments in muscle function after chronic incomplete spinal cord injury (SCI).Setting:University of Florida, Gainesville, FL, USA.Methods:Voluntary and electrically elicited contractile measurements were performed and voluntary activation deficits were quantitatively determined in the knee extensor and ankle plantar flexor muscle groups in 10 individuals with chronic incomplete SCI (C5-T8, ASIA C or D) and age-, gender-, height- and body weight matched healthy controls.Results:Persons with incomplete-SCI were able to produce only 36 and 24% of the knee extensor torque and 38 and 26% of the plantar flexor torque generated by noninjured controls in the self-reported less-involved and more-involved limbs, respectively (P<0.05). In addition, both indices of explosive or instantaneous muscle strength, torque200 (absolute torque reached at 200 ms) and the average rate of torque development (ARTD) were dramatically reduced in the ankle plantar flexor and knee extensor muscle groups in persons with incomplete-SCI. However, the deficit in instantaneous muscle strength was most pronounced in the ankle plantar flexor muscles, with an 11.7-fold difference between the torque200 measured in the self-reported more involved limb and a 5-fold difference in the less-involved limb compared to control muscles. Voluntary activation deficits ranged between 42 and 66% in both muscle groups. Interestingly, electrically elicited contractile properties did not differ between the groups.Conclusion:The resultant impact of incomplete-SCI is that affected muscles not only become weak, but slow to develop voluntary torque. We speculate that the large deficit in torque200 and ARTD in the ankle plantar flexors muscles of persons with incomplete-SCI may limit locomotor function. The results presented in this study provide a quantitative and sensitive assessment of muscle function upon which future research examining rehabilitation programs aimed at restoring muscle function and promoting functional recovery after incomplete-SCI may be based.

Resistance training and locomotor recovery after incomplete spinal cord injury: a case series.

Study design:Longitudinal intervention case series.Objective:To determine if a 12-week resistance and plyometric training program results in improved muscle function and locomotor speed after incomplete spinal cord injury (SCI).Setting:University research setting.Methods:Three ambulatory individuals with chronic (18.7±2.2 months post injury) motor incomplete SCI completed 12 weeks of lower extremity resistance training combined with plyometric training (RPT). Muscle maximum cross-sectional area (max-CSA) of the knee extensor (KE) and plantar flexor (PF) muscle groups was determined using magnetic resonance imaging (MRI). In addition, peak isometric torque, time to peak torque (T 20–80), torque developed within the initial 220 ms of contraction (torque220) and average rate of torque development (ARTD) were calculated as indices of muscle function. Maximal as well as self-selected gait speeds were determined pre- and post-RPT during which the spatio-temporal characteristics, kinematics and kinetics of gait were measured.Results:RPT resulted in improved peak torque production in the KE (28.9±4.4%) and PF (35.0±9.1%) muscle groups, as well as a decrease in T20–80, an increased torque220 and an increase ARTD in both muscle groups. In addition, an increase in self-selected (pre-RPT=0.77 m/s; post-RPT=1.03 m/s) and maximum (pre-RPT=1.08 m/s; post-RPT=1.47 m/s) gait speed was realized. Increased gait speeds were accompanied by bilateral increases in propulsion and hip excursion as well as increased lower extremity joint powers.Conclusions:The combination of lower extremity RPT can attenuate existing neuromuscular impairments and improve gait speed in persons after incomplete SCI.

Locomotor Training and Muscle Function After Incomplete Spinal Cord Injury: Case Series

Abstract Background/Objective: To determine whether 9 weeks of locomotor training (LT) results in changes in muscle strength and alterations in muscle size and activation after chronic incomplete spinal cord injury (SCI). Study Design: Longitudinal prospective case series. Methods: Five individuals with chronic incomplete SCI completed 9 weeks of LT. Peak isometric torque, torque developed within the initial 200 milliseconds of contraction (Torque200), average rate of torque development (ARTD), and voluntary activation deficits were determined using isokinetic dynamometry for the knee-extensor (KE) and plantar-flexor (PF) muscle groups before and after LT. Maximum muscle crosssectional area (CSA) was measured prior to and after LT. Results: Locomotor training resulted in improved peak torque production in all participants, with the largest increases in the more-involved PF (43.9% ± 20.0%), followed by the more-involved KE (21.1% ± 12.3%). Even larger improvements were realized in Torque200 and ARTD (indices of explosive torque), after LT. In particular, the largest improvements were realized in the Torque200 measures of the PF muscle group. Improvements in torque production were associated with enhanced voluntary activation in both the KE and ankle PF muscles and an increase in the maximal CSA of the ankle PF muscles. Conclusion: Nine weeks of LT resulted in positive alterations in the KE and PF muscle groups that included an increase in muscle size, improved voluntary activation, and an improved ability to generate both peak and explosive torque about the knee and ankle joints.

Non-invasive assessment of lower extremity muscle composition after incomplete spinal cord injury

Study Design:Cross-sectional study.Objective:(1) To quantify intramyocellular lipid (IMCL) content of the soleus muscle. (2) To assess the T2 relaxation rates in the lower extremity skeletal muscles in persons with incomplete spinal cord injury (SCI).Setting:Academic Institution, Florida.Methods:Eight subjects (42±10 years old; 70±12 kg; 176±10 cm) with chronic (17±9 months post injury) motor SCI (C4-T12; ASIA C or D) and eight matched healthy controls were tested. Localized unsuppressed proton spectroscopy (H-MRS) was performed to estimate total lipid content and individual lipid components; IMCL and extramyocellular lipid (EMCL) from the soleus muscle. T2-weighted imaging of lower extremity muscles yielded muscle T2 rates.Results:The IMCL content of the soleus muscle was 3.3 times higher in the patient group as compared to controls (P=0.002; 0.0401 (0.0234–0.0849) versus 0.0123 (0.0090–0.0175)). Similarly, EMCL measures were 4.5 times higher as compared to the controls (P=0.002). Significant differences were observed in the T2 relaxation times of the soleus and gastrocnemius muscles (P<0.05).Conclusion:The increased levels of IMCL might interfere with the glucose uptake in skeletal muscle; potentially predisposing persons with incomplete SCI to the development of peripheral insulin resistance. Marked elevations in the T2 relaxation times of the locomotor muscles are reflective of an altered muscle composition.