在辦公室或教室坐一整天,難免渾身僵硬,肩頸腰背酸痛。即使下班或下課後拼命運動,也很難抵消久坐帶來的不舒服。

除瞭難受,長時間的靜坐還會使人容易長胖,患2型糖尿病、腫瘤及心血管疾病的風險也升高[1]。知道久坐有害後,越來越多的人開始嘗試別的姿勢,甚至隨之出現瞭專供站立辦公的設備,比如可升降桌子、筆記本支架、可調高度的屏幕支架等。

用瞭這些設備,人們可以做到每天坐著的時間平均縮短1.3小時,站立時間增加1.4小時[1]。看似成效顯著,但別忘瞭減少久坐隻是手段,大傢改變姿勢目的是減少久坐帶來的健康危害、緩解身體的僵硬酸痛、預防打瞌睡或通過增加消耗來減肥。由坐到站,能不能實現這些目標?

站得那麼累,怎麼還算“久坐”

想知道站立是否有利,還得先看久坐為什麼有害。實際上,久坐行為的危害不在於“坐”,而在於很低的能量消耗。

其實不管你是坐、靠、躺還是站,無論在工作、玩遊戲或者坐車,隻要清醒狀態下能量消耗低於靜坐的1.5~2倍,都屬於久坐行為[1]。

對於多數人來說,僅僅站起來不能使能量消耗超出久坐范圍,也不能增加運動量[3, 4]。既然脫離不瞭久坐行為,站立的好處也存在疑問。

腰痛可能有效,其他不一定

為瞭健康站起來的人可能對下面的消息很失望:多數研究中,堅持間斷站立辦公數月時間,並不能明顯改善健康人的血壓、血糖及血脂水平,僅肥胖者的血糖水平可能有所好轉[1, 5]。

有人聽瞭會說“我站來又不是為瞭防病,隻是因為一直坐著太難受”。對於緩解身體僵硬酸痛,坐站交替可能優於久坐,特別是對於慢性腰痛的人[6, 7]。絕大多數人會都在一生中某個階段經歷腰痛,長時間靜坐可能加重癥狀[8]。在久坐辦公間歇適當站立,會使部分人的腰痛癥狀明顯減輕。

雖然站立可能緩解腰痛,但對肩頸、上肢不適及酸痛的作用有限[4, 9-11],還要親身嘗試才能知道對個人是否有效。對於下肢,站立姿勢反而比坐位更容易引起酸痛。

站立緩解酸痛的效果不一致,也與大傢姿勢不同有關。頸部、軀幹及下肢正確排列才能減輕疲勞,如果過度低頭、彎腰或始終將重心放在某一條腿上反而不舒服。

站立使我清醒?

除瞭身體僵硬酸痛,上班時的困倦也讓人難以抵抗。很多人看到支架上標註的“提高效率,活力加倍”,而期望站立如咖啡一般提神醒腦。

其實多數研究中,人們坐著與站著時的困倦程度及情緒並沒有明顯區別[12, 13]。少數人站立後感覺更有活力並且心情更好,另一些人站起來反而比持續坐著更疲勞[14, 15]。

既然不能提神醒腦,對於多數人來說,站與坐時的工作效率也沒有明顯區別 [16, 17]。當然瞭,上課犯困時被拎起來罰站聽講,是個例外。

減肥,還是別指望瞭

除瞭提高工作效率,站立辦公設備的宣傳裡還常有“消除贅肉”。確實一般人站著比坐著消耗能量稍多,但兩者差異並不大[18]。相對於坐著,站立1小時能量消耗隻多出4.2~10千卡[1],即使每天站立累計4小時,多消耗的熱量還抵不上兩小塊巧克力。

另外還有少數人非常擅長站,靜止站立時能量消耗甚至低於坐著。因此,嘗試用站代替坐來減肥的研究,都沒有得出站立瘦身的結果 [19-21]。

站久瞭還不如坐著

站著的獲益不是很確定,但久站的危害人們早就體會到瞭。早年間,很多工人都需要整日站著工作,不能坐下或來回走動。他們不僅飽受腰痛、腳痛、下肢靜脈曲張、腿腳水腫的折磨,女性還會因長時間站立增加早產及流產的風險[1]。

對於多數人,舒適的持續站立時間不超過15~30分鐘[22, 23]。如果為瞭減輕背部不適而站立,每次15分鐘就足夠瞭,持續站立時間過長反而難受[24]。

當靜止站立達到30分鐘時,小腿及足部的血流增多,疲勞、不適及疼痛的感覺開始出現[25]。已經存在外周血管疾病的人,應盡量避免連續站立30分鐘以上。如果工作需要連續站立2小時以上,可利用壓縮襪、地墊、鞋墊及坐站兩用凳子來緩解疲勞[25]。

多換姿勢,多活動

無論坐著還是站著,長時間的靜態姿勢都對健康不利並且導致身體酸痛不適。

想要改善身體僵硬及肌肉疲勞,關鍵在於經常變換姿勢,而不是長時間的持續站立[1]。對於減輕體重或久坐健康危害,進行比站立強度更大的活動,才有肯定的效果。

常年久坐不動的人,可以從工作中坐站交替及輕度體力活動開始,逐漸增加時間及活動強度。添置桌子或支架是途徑之一,多走動比靜靜站著更為有效[26]。

參考文獻

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作者:代天醫

編輯:odette