Reliability and Agreement of Intramuscular Coherence in Tibialis Anterior Muscle

Abstract

BackgroundNeuroplasticity drives recovery of walking after a lesion of the descending tract. Intramuscular coherence analysis provides a way to quantify corticomotor drive during a functional task, like walking and changes in coherence serve as a marker for neuroplasticity. Although intramuscular coherence analysis is already applied and rapidly growing in interest, the reproducibility of variables derived from coherence is largely unknown. The purpose of this study was to determine the test-retest reliability and agreement of intramuscular coherence variables obtained during walking in healthy subjects.Methodology/Principal FindingsTen healthy participants walked on a treadmill at a slow and normal speed in three sessions. Area of coherence and peak coherence were derived from the intramuscular coherence spectra calculated using rectified and non-rectified M. tibialis anterior Electromyography (EMG). Reliability, defined as the ability of a measurement to differentiate between subjects and established by the intra-class correlation coefficient, was on the limit of good for area of coherence and peak coherence when derived from rectified EMG during slow walking. Yet, the agreement, defined as the degree to which repeated measures are identical, was low as the measurement error was relatively large. The smallest change to exceed the measurement error between two repeated measures was 66% of the average value. For normal walking and/or other EMG-processing settings, not rectifying the EMG and/or high-pass filtering with a high cutoff frequency (100 Hz) the reliability was only moderate to poor and the agreement was considerably lower.Conclusions/significanceOnly for specific conditions and EMG-processing settings, the derived coherence variables can be considered to be reliable measures. However, large changes (>66%) are needed to indicate a real difference. So, although intramuscular coherence is an easy to use and a sufficiently reliable tool to quantify intervention-induced neuroplasticity, the large effects needed to reveal a real change limit its practical use.

A pilot study assessing reliability and age‐related differences in corticomuscular and intramuscular coherence in ankle dorsiflexors during walking

“…The same was observed for intraMC in the older adult group, whereas in young adults, intraMC showed fair reliability. This latter result matches closely with the previous results of intraMC (with regard to the magnitude of reliability and agreement estimates), which considered the same lower limb muscle (i.e., tibialis anterior) with younger adults but during gait performed on a treadmill (van Asseldonk et al, 2014). This indicates that intraMC has potential in experimental contexts aimed at exploring corticospinal control of gait dynamics provided that young adults and tibialis anterior muscles are the targets of an intervention and that swing phase of gait is the…”

“…One of the two pairs of bipolar electrodes was placed over the left tibialis anterior (TA) muscle, while the other was over the right TA muscle. In each pair, one sensor was placed proximally (TAprox) while the other was placed distally (TAdist) with respect to the muscle belly and according to previously described anatomical landmarks (de Bruin, Patt, Ringli, & Gennaro, ; Jensen et al, , ; Spedden et al, ; van Asseldonk et al, ). The interelectrode distance (electrodes’ center‐to‐center) was set to ~ 2 cm and the distance between bipolar configurations in each leg was ∼11 cm (σ: ∼2 cm; range: ∼7 cm to ∼14 cm), to reduce the risk of cross‐talk as well as the recording of muscle activity from overlapping motor unit areas (Hansen et al, ).…”

“…The obtained coherence was transformed to magnitude‐squared coherence by squaring the coherence estimation and it was considered significant if it exceeded a confidence limit (CL) with a probability of 95% (α = 0.05) and related to the number of segments used for the calculation of the coherence estimate by the following equation (Rosenberg, Amjad, Breeze, Brillinger, & Halliday, ):where N denotes the number of segments, represented by the number of heel strikes multiplied by the number of tapers used in the multi‐tapered spectral analysis. Although either a standard consensus or common practice in coherence analysis pipelines and procedures is lacking, a statistical test to infer on significant coherence estimates can be useful to control the inherent variability in coherence estimates related to the number of segments (e.g., number of heel strikes) used in the analysis (van Asseldonk et al, ) as well as avoiding spurious coherence values (Rosenberg et al, ). This method is widely used in literature on corticospinal control of gait (Jensen et al, , ; Petersen et al, ; Spedden et al, , ) as well as in studies on CMC using motor/low‐level force tasks (Chakarov et al, ; Kristeva, Patino, & Omlor, ; Omlor, Patino, Hepp‐Reymond, & Kristeva, ).…”

“…Despite the large body of studies employing CMC and in-traMC, to our knowledge, only few studies have investigated test-retest reliability of CMC (Pohja, Salenius, & Hari, 2005;Witham, Riddle, Baker, & Baker, 2011). Furthermore, solely one study assessed this during active gait, but employing only intraMC (van Asseldonk, Campfens, Verwer, Putten, & Stegeman, 2014). Studies on CMC reliability during walking seem not to be present.…”

Identification of connectivity in human motor control: exciting the afferent pathways

“…In the perturbed task, significant CMC was found on several non-stimulus frequencies as well; the likelihood of finding significant CMC at some harmonics of the stimulus frequencies (8,12 and 42Hz) was even comparable to the likelihood of finding CMC at the stimulus frequencies: more than 50% of the subjects had CMC on at least one of these frequencies. The CMC at non-stimulus frequencies may represent CMC generated by the same intrinsic mechanisms as in an unperturbed task.…”