Sling-based infant carrying affects lumbar and thoracic spine neuromechanics during standing and walking

Optical Marker-Based Motion Capture of the Human Spine: A Scoping Review of Study Design and Outcomes

Biomechanical analysis of the human spine is crucial to understanding injury patterns. Motion capture technology has gained attention due to its non-invasive nature. Nevertheless, traditional motion capture studies consider the spine a single rigid segment, although its alignment changes during movement. Moreover, guidelines that indicate where markers should be placed for a specific exercise do not exist. This study aims to review the methods used to assess spine biomechanics using motion capture systems to determine the marker sets used, the protocols used, the resulting parameters, the analysed activities, and the characteristics of the studied populations. PRISMA guidelines were used to perform a Scoping Review using SCOPUS and Web of Science databases. Fifty-six journal and conference articles from 1997 to 2023 were considered for the analysis. This review showed that Plug-in-Gait is the most used marker set. The lumbar spine is the segment that generates the most interest because of its high mobility and function as a weight supporter. Furthermore, angular position and velocity are the most common outcomes when studying the spine. Walking, standing, and range of movement were the most studied activities compared to sports and work-related activities. Male and female participants were recruited similarly across all included articles. This review presents the motion capture techniques and measurement outcomes of biomechanical studies of the human spine, to help standardize the field. This work also discusses trends in marker sets, study outcomes, studied segments and segmentation approaches.

The Application of Surface Electromyography Technology in Evaluating Paraspinal Muscle Function

Surface electromyography (sEMG) has emerged as a valuable tool for assessing muscle activity in various clinical and research settings. This review focuses on the application of sEMG specifically in the context of paraspinal muscles. The paraspinal muscles play a critical role in providing stability and facilitating movement of the spine. Dysfunctions or alterations in paraspinal muscle activity can lead to various musculoskeletal disorders and spinal pathologies. Therefore, understanding and quantifying paraspinal muscle activity is crucial for accurate diagnosis, treatment planning, and monitoring therapeutic interventions. This review discusses the clinical applications of sEMG in paraspinal muscles, including the assessment of low back pain, spinal disorders, and rehabilitation interventions. It explores how sEMG can aid in diagnosing the potential causes of low back pain and monitoring the effectiveness of physical therapy, spinal manipulative therapy, and exercise protocols. It also discusses emerging technologies and advancements in sEMG techniques that aim to enhance the accuracy and reliability of paraspinal muscle assessment. In summary, the application of sEMG in paraspinal muscles provides valuable insights into muscle function, dysfunction, and therapeutic interventions. By examining the literature on sEMG in paraspinal muscles, this review offers a comprehensive understanding of the current state of research, identifies knowledge gaps, and suggests future directions for optimizing the use of sEMG in assessing paraspinal muscle activity.

The Combined Influence of Infant Carrying Method and Motherhood on Gait Mechanics

Postpartum mothers are susceptible to lumbopelvic pain which may be exacerbated by loading, like carrying their infant in arms and with baby carriers. Nulliparous women carrying infant mannequins may biomechanically mimic mother-infant dyad, but this has not been studied. The purpose of our study was to investigate biomechanical differences of 10 mothers carrying their infants and 10 nulliparous women carrying infant mannequins under 3 gait conditions: carrying nothing, carrying in arms, and carrying in a baby carrier (babywearing). Spatiotemporal gait parameters, peak ground reaction forces and impulses, and lower extremity and trunk kinematics were collected using motion capture and force plates and compared using a mixed 2 × 3 (parity × condition) analysis of variance (α ≤ .05). The largest differences occurred between carrying conditions: carrying in arms or babywearing increased vertical and anteroposterior ground reaction forces, trunk extension, ankle dorsiflexion, and hip and knee flexion. Kinematic differences were identified between arms and babywearing conditions. Together this suggests alterations in joint loading for both groups. Our study also contributes a novel understanding of postpartum health by demonstrating alterations in step time, anterior forces, and ankle and knee mechanics, suggesting that during gait, mothers carrying their own infants choose different propulsive strategies than nulliparous women carrying mannequins.

Effects of infant care posture and weight on static postural balance

BACKGROUND

Studies investigating postural balance during various infant care postures have not been reported yet.

OBJECTIVE

The aim of this study was to measure static postural balance when holding an infant dummy in-arms and carrying an infant dummy on back according to different infant dummy weights.

METHODS

Sixteen healthy young subjects participated in a balance test. Infant dummies with weights of 4.6 kg (1-month) and 9.8 kg (12-month) were used in this study. All subjects were asked to naturally stand on a force platform in two infant care postures (holding an infant in-arms and carrying an infant on one's back). Center of pressure (COP) was measured from the force platform. Quantitative variables were derived from the COP. Two-way repeated measure analysis of variance (ANOVA) was performed to determine main effects of infant care postures, infant weight, and their interactions on COP variables.

RESULTS

Back carrying a 12-month infant dummy had the greatest amplitude in all COP variables. Back carrying posture showed significantly greater mean distance and peak power, faster mean velocity, and wider COP area compared to holding posture (P< 0.05). There were significant weight effects of most COP variables mainly in AP direction (P< 0.01).

CONCLUSIONS

Our results could contribute to the prevention of musculoskeletal diseases or prevention of fall due to various infant care activities by developing an assisting device to improve postural balance.

Scoping Review of Biological and Behavioral Effects of Babywearing on Mothers and Infants

OBJECTIVE

To synthesize the evidence on the biological and behavioral effects of babywearing on mothers and infants.

DATA SOURCES

We searched PubMed, CINAHL, Embase, PsycINFO, Sociological Abstracts, SCOPUS, and Google Scholar for peer-reviewed, full-text research articles published in English in which researchers reported on the biological or behavioral effects of babywearing on mothers or infants.

STUDY SELECTION

We reviewed the titles and abstracts of 200 records and abstracted 80 for full-text review. Of these, 29 studies met the eligibility criteria and were included in the review.

DATA EXTRACTION

We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) and extracted the following data from the included articles: author(s), year of publication, setting, aim/purpose, design, description, sample, results/outcomes, and implications to practice.

DATA SYNTHESIS

We synthesized data from the included studies into the following eight themes: Increased Contact, Responsiveness, and Secure Attachment; Physiologic Effects; Biomechanics and Positioning; Facilitating and Empowering; Comfort; Maternal Benefits; Speech, Vocalizations, and Tempo; and Beliefs and Perceptions About Babywearing.

CONCLUSION

Babywearing may have a range of beneficial biological and behavioral effects on mothers and infants. The evidence, however, is insufficient to inform practice recommendations, and additional research is warranted.

Analysis of maximum joint moment during infant lifting-up motion

BACKGROUND: Infant care activities can induce musculoskeletal disease. However, little is known about the biomechanical joint load during lifting-up of an infant. OBJECTIVE: The aim of this study was to investigate normalized maximum moment during lifting-up of infant dummies weighing 4.6 kg, 7.6 kg, and 9.8 kg. METHODS: Six healthy young subjects participated in our study. All subjects performed lifting-up activities of dummies to shoulder height with their feet apart and natural postures in their comfortable speed. Three-dimensional reflective marker trajectories and ground reaction forces were used as input to calculate joint moments using a full body musculoskeletal model. Joint moments were normalized by each subject’s body mass. Friedman’s test was performed to compare mean differences of normalized joint moments for lifting up three dummy weights. RESULTS: Lumbar joint had the greatest normalized joint moment. Lumbar and hip extension moments were significantly increased with dummy weight (P< 0.05). In contrast, knee extension and ankle plantarflexion moment were not significantly affected by dummy weight (P> 0.05). CONCLUSIONS: These results indicate that the lumbar joint plays the most important role in infant lifting-up motion and that the load of lumbar and hip joint should be reduced when lifting a heavier infant. These results could contribute to the development of an effective lifting strategy and an assisting device for lifting an infant.

Infant carrying method impacts caregiver posture and loading during gait and item retrieval

BACKGROUND

Human babies are carried by their caregivers during infancy, and the use of ergonomic aids to wear the baby on the body has recently grown in popularity. However, the effects of wearing or holding a baby in-arms on an individual's mechanics during gait and a common object retrieval task are not fully understood.

RESEARCH QUESTION

What are the differences in: 1) spatiotemporal, lower extremity kinematics, and ground reaction force variables during gait, and 2) technique, center of mass motion, and kinematics during an object retrieval task between holding and wearing an infant mannequin?

METHODS

In this prospective biomechanics study, 10 healthy females performed over-ground walking and an object retrieval task in three conditions, holding: (1) nothing (unloaded), (2) an infant mannequin in-arms, and (3) an infant mannequin in a baby carrier. Mechanics were compared using repeated measures ANOVA.

RESULTS

During gait, greater vertical ground reaction force and impulse and braking force was found during the in-arms and carrier conditions compared to unloaded. Significant but small (<5°) differences were found between conditions in lower extremity kinematics. Increased back extension was found during carrier and in-arms compared to unloaded. Step length was the only spatiotemporal parameter that differed between conditions. During object retrieval, most participants used a squatting technique to retrieve the object from the floor. They maintained a more upright posture, with less trunk flexion and anteroposterior movement of their center of mass, and also did not try to fold forward over their hips during the two loaded conditions. Lower extremity kinematics did not differ between unloaded and carrier, suggesting that babywearing may promote more similar lower extremity mechanics to not carrying anything.

SIGNIFICANCE

Holding or wearing an infant provides a mechanical constraint that impacts the forces and kinematics, which has implications for caregivers' pain and dysfunction.