不同年齡族群單、雙腳坐站測試與肌肉量、下肢肌力之相關性：橫斷性研究

Abstract

目的：台灣邁入超高齡化社會，預防與延緩失能成了重要的議題。40歲過後的中年人，肌肉量大約每年以1%的速度流失，肌力每10年平均減少8%，出現行動緩慢、吃力，影響往後的功能性表現、行動能力與生活品質。中年人應提早預防肌力退化，但缺乏合適的檢測工具。坐站測試 (sit-to-stand, STS) 為評估下肢功能性肌力的重要工具，然而傳統雙腳坐站測試缺乏針對較年輕族群的驗證，可能不足以挑戰高功能族群，能否篩檢中年人早期肌力衰退仍有待釐清。故本研究旨在比較不同年齡族群5次雙腳與單腳坐站測試之表現差異，並探討坐站表現指標與肌肉量、下肢肌力之相關性與預測能力。方法：本研究採橫斷式觀察設計，招募50位20到69歲健康、可獨立坐站的受試者 (39位女性，平均年齡44.8 ± 14.3歲)，每10歲為區間分為五組 (20、30、40、50及60歲組)。受試者接受身體組成、5次雙腳坐站、5次單腳坐站和下肢徒手最大肌力測試。坐站過程中除採計完成次數和時間外，另以測力板量測尖峰地面反作用力 (peak ground reaction force, peak GRF) 與發力率 (rate of force development, RFD) 等動力學指標。結果：所有年齡組皆可完成5次雙腳坐站，而單腳坐站完成次數隨年齡增加而下降。雙腳坐站完成時間與RFD隨年齡增加而衰退，但組間無顯著差異，而雙腳坐站peak GRF (含經體重標準化) 隨年齡顯著下降且具有顯著組間差異。單腳坐站的完成時間和peak GRF (含經體重標準化) 皆呈現顯著年齡組間差異，但單腳RFD與年齡無顯著相關。分析與肌肉量相關性，單、雙腳坐站完成時間與肌肉量皆無顯著相關；反之，單、雙腳peak GRF與RFD均與多項肌肉量指標呈中度至高度正相關，當中單腳peak GRF與骨骼肌質量指數SMI的相關性最高 (ρ = .818, p < .001)。迴歸分析顯示，peak GRF對肌肉量指標具有高度且顯著的線性預測力，且單腳peak GRF之解釋力優於雙腳 (雙腳R2 = .621- .654；單腳R2 = .679- .755)。下肢徒手肌力與單、雙腳坐站完成時間呈低至中度負相關，雙腳坐站之peak GRF (含經體重標準化) 與下肢肌力呈中至高度正相關，但單腳坐站之peak GRF與肌力相關性較弱，惟其RFD與所有下肢肌力變項呈高度正相關。迴歸預測方面，單腳RFD可有效預測髖伸直肌力 (R² = .529，q < .001)，雙腳坐站則無任何指標可達到解釋 ≥ 50%肌力變異的模型。結論：本研究顯示，雙腳與單腳坐站測試各具評估優勢，時間指標在較年輕族群的辨識能力有限，若要提升中年早期肌肉功能衰退的篩檢，應加入測力板的動力學指標。Peak GRF (尤其單腳) 最能反映並預測肌肉量，而單腳RFD可預測下肢徒手肌力。建議未來在功能評估與臨床篩檢中，結合不同坐站型式與力學指標，以提升社區與臨床對早期肌肉功能衰退之偵測效能。

Purpose: As Taiwan enters a super-aged society, preventing and delaying disability has become a critical public health issue. After the age of 40, muscle mass declines at an approximate rate of 1% per year, while muscle strength decreases by an average of 8% per decade, leading to slower movement, increased physical effort, and subsequent impairments in functional performance, mobility, and quality of life. Early prevention of muscle strength decline in midlife is therefore essential; however, appropriate screening tools remain limited. The sit-to-stand (STS) test is widely used to evaluate functional lower-limb strength, yet the conventional double 5-times STS has been insufficiently validated in younger and higher-functioning populations and may not be challenging enough for high-functioning individuals. Its ability to detect early strength decline in midlife remains unclear. Therefore, this study aimed to compare performance differences in 5-times single- and double-leg STS tests across different age groups and to examine the associations and predictive capacity of STS performance indicators for muscle mass and lower-limb manual muscle strength. Methods: This cross-sectional observational study recruited 50 healthy adults aged 20-69 years (39 females; mean age 44.8 ± 14.3 years), who were stratified into five age groups by decade (20s, 30s, 40s, 50s, and 60s). Participants underwent assessments of body composition, five-times double-leg STS, five-times single-leg STS, and maximal lower-limb manual muscle test using handheld dynamometry. During the STS tasks, completion repetitions, time and kinetic parameters were recorded, including peak ground reaction force (peak GRF) and rate of force development (RFD) were measured using force plates. Results: All age groups were able to complete five repetitions of the double-leg STS, whereas the number of completed repetitions during the single-leg STS declined with increasing age. Double-leg STS completion time and RFD showed age-related declines but did not differ significantly between age groups. In contrast, double-leg STS peak GRF (both absolute and body-weight-normalized) declined significantly with age and demonstrated significant between-group differences. For the single-leg STS, completion time and peak GRF (absolute and normalized) showed significant age-group differences, whereas single-leg RFD was not significantly associated with age. Regarding associations with muscle mass, completion time for both double- and single-leg STS was not significantly associated with any muscle mass index; conversely, both double- and single-leg peak GRF and RFD demonstrated moderate to strong positive correlations with multiple muscle mass indices, with the strongest association observed between single-leg peak GRF and skeletal muscle mass index (SMI) (ρ = .818, p < .001). Regression analyses further showed that peak GRF had strong and significant linear predictive power for muscle mass, and single-leg peak GRF explained more variance than double-leg (double-leg R² = .621- .654; single-leg R² = .679- .755). Lower-limb manual muscle test showed weak-to-moderate negative correlations with double- and single-leg STS completion time. Double-leg STS peak GRF (absolute and normalized) showed moderate to strong positive correlations with lower-limb muscle strength, whereas single-leg peak GRF exhibited weaker associations. Notably, single-leg RFD demonstrated strong positive correlations with all lower-limb muscle strength. In regression models, single-leg RFD significantly predicted hip extensor strength (R² = .529, q < .001), whereas no double-leg STS indicator explained ≥ 50% of the variance in strength. Conclusions: This study demonstrates that double- and single-leg STS offer complementary assessment advantages, and time-based indicators have limited discriminatory ability in high-functioning individuals. To enhance screening for early muscle functional decline in midlife, force plate should be incorporated. Peak GRF, particularly single-leg STS, best reflects and predicts muscle mass, while single-leg RFD predicts lower-limb strength. Future functional assessments and screening may benefit from integrating different STS modalities with kinetic measures to improve the early detection of muscle functional deterioration in community and clinical settings.