Original ArticleIncreased Co-contraction Activity During Push-Off Phase of Walking in Healthy Women
Graphical abstract
Introduction
Knee-joint movement during walking is mainly controlled by the two foremost muscle groups of the thigh, hamstrings and quadriceps femoris (QF), which are considered antagonist groups for the motor task [1]. Hamstrings and QF are strictly involved in preserving stability of knee joint, together with tendons, cartilages and ligaments. However, injuries and/or disorders could affect each one of those structures, both in daily life conditions and during sport activities [2].
Muscular co-contraction is typically employed by human neuro-muscular system as a primary strategy for enhancing joint stiffness, postural balance, and motion accuracy in dynamic condition, such as walking [3], [4]. Thus, this physiological phenomenon is one of the main factors which contribute improving the whole walking stability and preventing joint lesions [3], [4], [5], [6]. Muscular co-contractions during walking have been widely investigated in both physiological and pathological context [3], [4], [5], [6], [7], [8], [9]. Recently, the present group of researchers presented for the first time a comprehensive analysis of thigh-muscle co-contraction throughout healthy-adult walking [5]. The study focused on processing the surface electromyographic (sEMG) signal in order to identify and quantify thigh-muscle co-contraction during healthy-adult walking, in terms of co-contraction intervals and frequency of co-contraction occurrence. Results, computed in a significant number of strides (nearly 15.000 strides in total), showed that QF/hamstrings co-contractions were detected very frequently (90% of strides) during weight acceptance and swing and more rarely during mid-stance (25% of strides). Identifying the frequency of occurrence, in addition to co-contraction timing, could be useful for deepening the clinical interpretation of the role of muscular co-contraction and control and stabilization of knee joint in clinical environment.
EMG-based studies in able-bodied adult subjects showed that co-contraction activity of lower-limb muscle during walking could be influenced by age and velocity [8], [10], [11], [12]. Recently, literature focused also on the effect of gender on that phenomenon. In particular, an increased occurrence of ankle-muscle co-contractions (gastrocnemius lateralis vs. tibialis anterior) was found in a population of 15 healthy females vs. 15 age-matched males, in presence of no significant alterations of co-contraction timing [13]. The higher occurrence of co-contraction in female population was quantified in the different gait phases: 115% increase in early stance, 60% in mid-stance, 134% in pre-swing, and 43% in swing. To the best of our knowledge, no data on the effect of gender on muscular co-contraction at knee joint are available in scientific literature, except for a preliminary attempt [14]. However, information in this regard should be considered for discriminating pathological from physiological behaviour typical of the female (or male) population. For instance, thigh-muscle co-contractions seem to play a role in the increased rate of knee sprain in females and could be also involved in the female higher risk of anterior cruciate ligament lesion [2].
Thus, the present study was designed to assess the possible gender-related differences in the co-contraction activity of QF vs. hamstring muscles in able-bodied adults, during straight walking at self-selected speed and cadence. To this aim, medial hamstrings (MH) were selected as representative muscles of hamstring group. Vastus lateralis (VL) and rectus femoris (RF) were chosen for QF group. sEMG signals from MH, VL and RF were processed in order to provide a reliable quantification of gender-related differences in terms of both co-contraction timing and frequency of occurrence, as suggested by the outcomes reported in [13]. Since co-contractions showed age dependency, age-matched subjects were recruited in order to avoid possible bias of age. To handle and describe the expected inter and intra subject variability of the muscular co-contraction, numerous strides (mean value of strides per subject) were included in the study.
Section snippets
Subjects
Thirty able-bodied volunteer subjects were retrospectively involved in the study. The whole population was split into two groups: F-group (15 females: ) and M-group (15 males, age: years). Table 1 summarizes the main characteristics of subjects (mean ±SD and range). Age-matched participants were carefully recruited in order to avoid possible bias of age. Exclusion criteria: necessity of aided walking, neuromuscular diseases, disorders in balance and previous surgical
Temporal gait parameters
An average value per subject (± standard deviation, SD) of strides (M-group) and strides (F-group) was analysed. Results were reported as mean value over right and left lower limbs. From the total of 16315 strides analysed, 1315 strides (8% of total strides) were rejected from the analysis because not following the H–F–P–S foot-floor-contact pattern and/or being outlier cycles relative to deceleration, reversing, and acceleration. The mean (±SD) duration of H, F, P and S phases
Discussion
The present study was designed to quantitatively assess gender-related differences in co-contraction patterns of QF and hamstring muscles in healthy adults, during walking at self-selected pace. In agreement with literature [21], [22], [23], thigh muscles revealed a high degree of variability in both male and female populations in terms of activation modalities assumed during walking and number of strides where each modality occurred. For each muscle, every subject adopted the same three main
Conclusion
The present study provides a reference frame for knee muscle co-contractions during walking, differentiated for women and men. The concomitant analysis of timing and frequency of co-contraction occurrences denotes a significant increase in females of QF/hamstrings co-contraction recruitment in push-off. This suggests a female attempt to augment the level of knee-joint stabilization in the final phase of single support when control of balance is thornier. Future studies are evoked in order to
Human and animal rights
The authors declare that the work described has been carried out in accordance with the Declaration of Helsinki of the World Medical Association revised in 2013 for experiments involving humans as well as in accordance with the EU Directive 2010/63/EU for animal experiments.
Informed consent and patient details
The authors declare that this report does not contain any personal information that could lead to the identification of the patient(s).
Funding
This work did not receive any grant from funding agencies in the public, commercial, or not-for-profit sectors.
Author contributions
All authors attest that they meet the current International Committee of Medical Journal Editors (ICMJE) criteria for Authorship.
CRediT authorship contribution statement
A. Strazza: Formal analysis, Writing - original draft. A. Mengarelli: Data curation, Investigation. F. Verdini: Investigation, Writing - review & editing. S. Cardarelli: Formal analysis, Software. A. Tigrini: Data curation, Visualization. C. Morbidoni: Software, Validation, Resources, Supervision. S. Fioretti: Resources, Supervision. F. Di Nardo: Conceptualization, Investigation, Methodology, Project administration, Writing - original draft.
Declaration of Competing Interest
The authors declare that they have no known competing financial or personal relationships that could be viewed as influencing the work reported in this paper.
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