Voluntary Movement Frequencies in Submaximal One- and Two-Legged Knee Extension Exercise and Pedaling

Abstract

Understanding of behavior and control of human voluntary rhythmic stereotyped leg movements is useful in work to improve performance, function, and rehabilitation of exercising, healthy, and injured humans. The present study aimed at adding to the existing understanding within this field. To pursue the aim, correlations between freely chosen movement frequencies in relatively simple, single-joint, one- and two-legged knee extension exercise were investigated. The same was done for more complex, multiple-joint, one- and two-legged pedaling. These particular activities were chosen because they could be considered related to some extent, as they shared a key aspect of knee extension, and because they at the same time were different. The activities were performed at submaximal intensities, by healthy individuals (n = 16, thereof eight women; 23.4 ± 2.7 years; 1.70 ± 0.11 m; 68.6 ± 11.2 kg). High and fair correlations (R-values of 0.99 and 0.75) occurred between frequencies generated with the dominant leg and the nondominant leg during knee extension exercise and pedaling, respectively. Fair to high correlations (R-values between 0.71 and 0.95) occurred between frequencies performed with each of the two legs in an activity, and the two-legged frequency performed in the same type of activity. In general, the correlations were higher for knee extension exercise than for pedaling. Correlations between knee extension and pedaling frequencies were of modest occurrence. The correlations between movement frequencies generated separately by each of the legs might be interpreted to support the following working hypothesis, which was based on existing literature. It is likely that involved central pattern generators (CPGs) of the two legs share a common frequency generator or that separate frequency generators of each leg are attuned via interneuronal connections. Further, activity type appeared to be relevant. Thus, the apparent common rhythmogenesis for the two legs appeared to be stronger for the relatively simple single-joint activity of knee extension exercise as compared to the more complex multi-joint activity of pedaling. Finally, it appeared that the shared aspect of knee extension in the related types of activities of knee extension exercise and pedaling was insufficient to cause obvious correlations between generated movement frequencies in the two types of activities.

Repeated Bout Rate Enhancement Is Elicited by Various Forms of Finger Tapping

“…Though, it is considered that control of rhythmic movement is similar in animals and humans ( Dimitrijevic et al, 1998 ; Zehr, 2005 ; Hansen, 2015 ). To increase our understanding, studies applying reflex modulation during, for example, arm cycling and pedalling ( Zehr et al, 2007 ; Hundza and Zehr, 2009 ), voluntary pedalling ( Sakamoto et al, 2007 ; Hansen and Ohnstad, 2008 ; Stang et al, 2016 ), and finger tapping ( Shima et al, 2011 ; Hansen et al, 2015 ; Mora-Jensen et al, 2017 ) have been performed. Such studies reflect that investigation of CPG-mediated voluntary rhythmic movement in humans is challenged by the restricted access to the spinal cord ( Dietz, 2003 ; Zehr, 2005 ).…”

The role of stride frequency for walk-to-run transition in humans

“…With regard to generation of locomotion in general as well as to the more specific focus of the present study, two considerations are of particular relevance. Initially, a common understanding of the generation of locomotion 17 , 18 as well as rhythmic movement in general 19 is that the spinal neural networks, termed central pattern generators (CPGs), play a key role. The CPGs are considered to mediate an organized pattern of motor activity in combination with adequate supraspinal descending and peripheral afferent influences.…”

Lower limb joint angle variability and dimensionality are different in stairmill climbing and treadmill walking

“…A linear relationship between the PSF during walking and the PSF during running in healthy individuals has been suggested to indicate that the two gait modalities share a common neural drive from the CPG [45]. Furthermore, a high correlation ( r = 0.94) has been observed between the freely chosen frequencies during knee extension exercise for each leg and fair correlation ( r = 0.71) has been observed between the freely chosen pedaling frequencies during one-legged cycling for each leg [46]. The authors of the aforementioned studies suggested that these significant correlations could indicate that the CPGs of the two legs share a common frequency generator or that separated frequency generators of each legs are attuned via interneuronal connections [46].…”

“…Furthermore, a high correlation ( r = 0.94) has been observed between the freely chosen frequencies during knee extension exercise for each leg and fair correlation ( r = 0.71) has been observed between the freely chosen pedaling frequencies during one-legged cycling for each leg [46]. The authors of the aforementioned studies suggested that these significant correlations could indicate that the CPGs of the two legs share a common frequency generator or that separated frequency generators of each legs are attuned via interneuronal connections [46]. Adopting a similar approach in the present study, where the PSF during stairmill climbing and the stepping frequency during walking at PWS were not significantly correlated, would suggest that control of the rhythmic muscle activation during these tasks does not share a common neural drive from the CPG.…”