Impact of Unilateral Handbag Loads on Spine–Hip Kinematics and Paraspinal Muscle Activities: A PCA-Based Analysis

Abstract

Unilateral handbag carriage is a common practice in daily life, which imposes asymmetric demands on the trunk. This study examined the resulting kinematic and muscular adaptations during walking in 22 healthy male adults who carried a unilateral 5 kg handbag. Principal component analysis (PCA) was used to analyze spine–hip kinematics and paraspinal EMG, and its robustness was confirmed through component stability and sensitivity analyses. Load carriage significantly altered both kinematics (Pillai's trace = 0.978, p < 0.001) and muscular activations (Pillai's trace = 0.745, p < 0.001). Six kinematic and two muscular principal components (PC) explained 95% of the variance. Kinematic adaptations to load were driven by axial rotation at L3–L4 (31.0% contribution), lateral bending at T8–T9 (36.5% contribution), and flexion/extension at L3–L4 (73.9%), particularly in PCs 2, 4, and 5. Muscular changes were dominated by increased activation in the longissimus (d = 1.493, p < 0.001) and iliocostalis (d = 0.663, p = 0.02) on the side contralateral to the carried bag, and reflected in PCs 1 and 2. Complementary univariate analyses confirmed reduced thoracolumbar mobility and elevated contralateral paraspinal activation ( adjusted p < 0.05). Together, these findings demonstrate an integrated compensatory strategy adjustment under asymmetric load. The robustness of the methodology was confirmed via PC jackknife and bootstrap analyses; however, the findings are based on healthy young male participants under a fixed 5 kg load, acknowledging limited generalizability.

Keywords

• unilateral load carrying
• spine–hip kinematics
• paraspinal muscles
• multivariate analysis
• principal components

Tek Taraflı El Çantası Taşınmasının Omurga–Kalça Kinematiği ve Paraspinal Kas Aktiviteleri Üzerine Etkisi: PCA Tabanlı Bir Analiz

Abstract

Tek taraflı el çantası taşımak, günlük yaşamda yaygın bir uygulamadır ve gövde üzerinde asimetrik talepler oluşturur. Bu çalışma, tek taraflı 5 kg’lık bir el çantasını taşıyan 22 sağlıklı erkek yetişkinin yürüyüşü sırasında ortaya çıkan kinematik ve kas uyumlarını incelemiştir. Temel bileşen analizi (PCA), omurga–kalça kinematiği ve paraspinal EMG verilerini çözümlemede kullanılmış; yöntemin sağlamlığı bileşen kararlılığı ve duyarlılık analizleriyle doğrulanmıştır. Yük taşıma, hem kinematikleri (Pillai’s trace = 0.978, p < 0.001) hem de kas aktivasyonlarını (Pillai’s trace = 0.745, p < 0.001) anlamlı şekilde değiştirmiştir. Altı kinematik ve iki kas temelli temel bileşen (PC), toplam varyansın %95’ini açıklamıştır. Kinematik uyumlar, özellikle L3–L4 düzeyinde aksiyel rotasyon (%31.0 katkı), T8–T9 düzeyinde lateral fleksiyon (%36.5 katkı) ve L3–L4 düzeyinde fleksiyon/ekstansiyon (%73.9 katkı) ile yönlendirilmiş, bu etkiler özellikle PC2, PC4 ve PC5’te belirgin olmuştur. Kas değişiklikleri, taşınan çantanın karşı tarafındaki longissimus (d = 1.493, p < 0.001) ve iliocostalis (d = 0.663, p = 0.02) kaslarında artan aktivasyonla baskın hale gelmiş ve bu değişimler PC1 ve PC2’de yansımıştır. Tamamlayıcı tek değişkenli analizler, torakolomber hareketliliğin azaldığını ve karşı taraf paraspinal aktivasyonunun arttığını (düzeltilmiş p < 0.05) doğrulamıştır. Bu bulgular, asimetrik yük altında bütünleşik bir telafi edici strateji ayarlanmasının ortaya çıktığını göstermektedir. Yöntemin sağlamlığı, PC jackknife ve bootstrap analizleri ile doğrulanmıştır; ancak bulgular, sabit 5 kg yük altında test edilen sağlıklı genç erkek katılımcılarla sınırlıdır ve genellenebilirliğin kısıtlı olduğu kabul edilmektedir.

Keywords

• tek taraflı yük taşıma
• omurga–kalça kinematiği
• paraspinal kaslar
• çok değişkenli analiz
• temel bileşenler

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