Test Battery Designed to Quickly and Safely Assess Diverse Indices of Neuromuscular Function After Unweighting

Abstract

Adequately describing the functional consequences of unweighting (e.g., bed rest, immobilization, spaceflight) requires assessing diverse indices of neuromuscular function (i.e., strength, power, endurance, central activation, force steadiness). Additionally, because unweighting increases the susceptibility of muscle to damage, testing should consider supplementary safety features. The purpose of this study was to develop a test battery for quickly assessing diverse indices of neuromuscular function. Commercially available exercise equipment was modified to include data acquisition hardware (e.g., force plates, position transducers) and auxiliary safety hardware (e.g., magnetic brakes). Ten healthy, ambulatory subjects (31 ± 5 years, 173 ± 11 cm, 73 ± 14 kg) completed a battery of lower- and upper-body neuromuscular function tests on 3 occasions separated by at least 48 hours. The battery consisted of the following tests, in order: (1) knee extension central activation, (2) knee extension force steadiness, (3) leg press maximal strength, (4) leg press maximal power, (5) leg press power endurance, (6) bench press maximal strength, (7) bench press force steadiness, (8) bench press maximal power, and (9) bench press power endurance. Central activation, strength, rate of force development, maximal power, and power endurance (total work) demonstrated good-to-excellent measurement reliability (SEM = 3-14%; intraclass correlation coefficient [ICC] = 0.87-0.99). The SEM of the force steadiness variables was 20-35% (ICC = 0.20-0.60). After familiarization, the test battery required 49 ± 6 minutes to complete. In conclusion, we successfully developed a test battery that could be used to quickly and reliably assess diverse indices of neuromuscular function. Because the test battery involves minimal eccentric muscle actions and impact forces, the potential for muscle injury has likely been reduced.

Low-Budget Instrumentation of a Conventional Leg Press to Measure Reliable Isometric-Strength Capacity

“…The comparison of absolute values of maximum strength remains difficult because kinematics of force transmission can differ substantially between leg-press devices. Mean maximum-strength values of 1334 N in young healthy women show good validity compared with the values of Müller et al 1 and Spiering et al 4 RFD can be expressed as in the case at hand with the maximum rate of force rise at the beginning of contraction, it can be depicted as the maximum or mean rate of force rise in different time windows starting at contraction onset, 2,6 or it can be derived from a certain range of percentage of maximum strength during force rise (eg, 10-40% of measured maximum force). 10 Since no clear consensus exists, comparison between protocols is impaired.…”

“…Nevertheless, the current ICC results for RFD (.93) are in line with published 2-legged measurement (.94). 4 Taking the test-retest variability and the bias (and LoA) into account, percentage and absolute values might serve as an indication for interpretations of true intervention effects (Table 1).…”

“…This would allow widespread quality control of training or rehabilitation interventions. 4 Muscle strength, defined as the capability of the neuromuscular system to generate force, is required for daily life tasks and is essential for athletic performance. Evaluation of muscle strength must be reliable to appraise effects of training or rehabilitation.…”

Physiological and Functional Alterations after Spaceflight and Bed Rest

“…In this study, the twitch interpolation method was used to assess neuromuscular drive during knee extensions and details of the test in this study have been described previously ( 21 ). In this test, subjects sat in a modified knee extension device (NT-1220; Nautilus, Inc., Vancouver, WA) equipped with a load cell (Transducer Techniques, Temecula, CA) and customized for isometric strength testing.…”

Maximal strength training: the impact of eccentric overload

“…RFD was calculated as ⌬force/⌬time in the time intervals 0 -30, 0 -50, 0 -100, 0 -150, and 0 -200 ms, where 0 ms denotes the onset of concentric force production, along with maximal RFD in the steepest part of the force-time curve. In leg press 1RM and RFD, an ICC of 0.99 and 0.94, respectively, has been documented (Spiering et al 2011).…”