低量高強度間歇訓練的生理適應

PHYSIOLOGICAL ADAPTATIONS TO LOW-VOLUME HIGH-INTENSITY INTERVAL TRAINING

低量高強度間歇訓練的生理適應

Martin J. Gibala

KEY POINTS

·         High-intensity interval training (HIIT) is generally characterized by repeated sessions of brief, intermittent exercise, typically at intensities that elicit ≥85% of peak oxygen uptake (VO₂peak), and interspersed by periods of rest or low-intensity exercise for recovery.
高強度間歇訓練(HIIT)通常指的是反覆性的短暫間歇性運動，通常是使用能誘發≥85%的攝氧峰值(VO₂peak/VO₂max)的運動強度，運動回合間穿插著休息或低強度的運動來幫助恢復

·         While long appreciated by endurance athletes as an integral component of training programs designed to maximize performance, short-term studies lasting up to several weeks in healthy persons of average fitness have established that HIIT per se is a potent stimulus to induce physiological adaptations that resemble changes typically associated with traditional endurance training, despite a lower total exercise volume and reduced training time commitment.
此種訓練方式長期受到耐力運動員的重視(因其對於設計來最大化運動表現的訓練計劃來說，是不可或缺的組件)，在針對一般體能水平的健康者持續數周的短期研究中已經證實HIIT本身對引發"通常與傳統耐力訓練相關的類似的生理適應變化"是一個強而有力的刺激(總訓練量比較低、投入的訓練時間也減少)

·         As little as six sessions of HIIT over 2 wk, using a protocol that entails only 2-3 min of all-out exercise within a training session that lasts ~20 min (i.e., repeated Wingate Tests), can increase skeletal muscle oxidative capacity, reduce non-oxidative energy provision during submaximal exercise and markedly improve performance during tasks that rely mainly on aerobic energy metabolism.
僅兩周共六次的HIIT訓練課，在持續大約20分鐘的訓練課中使用總合僅2-3分鐘的全力運動(指的是運動間歇期的時間加總，非指單一運動間歇回合就達2-3分鐘)即可增加骨骼肌的氧化能力、減少在次最大運動中的無氧能量供應，並顯著的增進"主要仰賴有氧能量代謝的任務"表現

·         While all-out HIIT protocols are very effective, other low-volume HIIT models that consist of relatively intense, but submaximal, constant-load efforts (e.g., 10 x 60 s at a fixed work intensity that elicits ~90% of maximal heart rate, interspersed by 60 s of recovery) have been shown to induce rapid physiological and performance adaptations similar to Wingate-based training.
全力以赴的HIIT訓練方式十分有效，其他那些由相對激烈但為次最大強度的恆定負荷努力(10個回合、每回合60秒在能誘發大約90%最大心跳率的固定做功強度下之運動，運動回合間穿插60秒的恢復)所組成的HIIT模型也被證實能誘發相似於Wingate-based訓練的快速生理與表現適應

·         The majority of low-volume HIIT studies conducted to date have utilized relatively short intervention periods (i.e., lasting up to several weeks) and future work involving long-term (i.e., months to years) interventions is needed to advance our mechanistic understanding of how manipulating the exercise stimulus translates into physiological remodeling, as well as identifying from a practical perspective the minimum “dose” of HIIT to maximize adaptation, given that lack of time remains the most commonly cited barrier to lack of regular exercise participation.

截至今日，大多數的低訓練量HIIT研究都是使用相對短的介入時間(持續數周)，在未來透過長期的介入的研究(月到年)來提升我們對「如何調控這些運動刺激對生理重塑的機制」，以及「從實際的視角來辨別最大化適應所需的最低HIIT劑量(因為缺乏時間仍然大眾缺乏規律運動的最大阻礙)」的了解

INTRODUCTION

Regular endurance training improves performance during tasks that rely mainly on aerobic energy metabolism, in large part by increasing the body’s ability to transport and utilize oxygen, and enhancing the capacity for the oxidative metabolism of substrates by working skeletal muscle (Saltin & Gollnick, 1983).

規律性的耐力訓練能增進"主要仰賴有氧能量代謝的任務"之表現，很大一部分是透過改善身體運輸與使用氧氣的能力，以及增進工作骨骼肌基質氧化代謝的能力(Saltin & Gollnick, 1983)

While less widely appreciated, high-intensity interval training (HIIT) is a potent stimulus to induce physiological adaptations that resemble, and indeed may be superior to, changes typically associated with traditional endurance training (Kubukeli et al., 2002; Ross & Leveritt, 2001).

而未引起廣泛重視的是：高強度間歇訓練(HIIT)是一個「對於誘發相似於一般與傳統耐力訓練相關之生理適應的變化」的強而有力刺激(事實上可能效果還更好) (Kubukeli et al., 2002; Ross & Leveritt, 2001)

Indeed, highly-trained endurance athletes have long incorporated HIIT as an integral component of training programs designed to maximize performance (Laursen & Jenkins, 2002). Recently, short-term studies lasting up to several weeks in healthy persons of average fitness have established that HIIT per se is a potent stimulus to induce physiological adaptations that resemble changes typically associated with traditional endurance training, despite a lower total exercise volume and reduced training time commitment (Burgomaster et al., 2005; Gibala et al., 2006; Little et al., 2010).

確實受高度訓練的運動員已經長期使用HIIT作為「設計來最大化表現的訓練計劃」中的重要組件(Laursen & Jenkins, 2002)

近期於一般體能水平健康者之短期研究(持續數周)已經證實HIIT本身對引發通常與傳統耐力訓練相關的類似的生理適應變化是一個強而有力的刺激(儘管總訓練量比較低、投入的訓練時間也減少) (Burgomaster et al., 2005; Gibala et al., 2006; Little et al., 2010).

This brief review highlights recent work that sheds new light on the potency of low-volume HIIT to induce rapid physiological remodeling and enhance the capacity for performance during tasks that rely mainly on aerobic energy metabolism. For a more comprehensive analysis, as well as the potential application of HIIT to different populations, the reader is referred to other recent reviews by the present author (Gibala et al., 2012, 2014) and others, including work that has specifically focused on those at risk for, or afflicted by, cardiometabolic disorders (Kessler et al., 2012; Weston et al., 2014). With regard to practical applications and training prescription, two other recent reviews (Buchheit & Laursen, 2013ab) consider in detail various aspects of HIIT programming, with a particular focus on athletic performance.

這篇簡短的概述彙整了近期那些揭示了低量的HIIT訓練能誘發迅速的生理重塑與增進主要依賴有氧能量代謝任務表現的潛力之研究

從更全面的分析與針對HIIT運用在不同族群上的潛力來看，以及，讀者們可以參考作者(Gibala et al., 2012, 2014)與其他包括特別聚焦在為代謝疾病所苦(或有風險)的族群之研究(Kessler et al., 2012; Weston et al., 2014)

關於實際上的運用與訓練處方開立，近期兩篇聚焦在運動表現上的研究有針對HIIT訓練計劃的不同面向進行詳細的討論(Buchheit & Laursen, 2013ab)

RESEARCH REVIEW – WHAT IS HIIT?研究回顧-HIIT是什麼？

High-intensity interval training (HIIT) is generally characterized by repeated sessions of brief, intermittent exercise, typically at intensities that elicit ≥85% of peak oxygen uptake (VO₂peak), and interspersed by periods of rest or low-intensity exercise for recovery.

高強度間歇訓練(HIIT)通常指的是反覆性的短暫間歇性運動，通常是使用能誘發≥85%的攝氧峰值(VO₂peak/VO₂max)的運動強度，運動回合間穿插著休息或低強度的運動來幫助恢復

A wide range of terms have been used to describe various interval training protocols, leading to many different acronyms and a general lack of standardization in the literature. A classification scheme was recently proposed in which the term “HIIT” is used to describe protocols in which the training stimulus is “near maximal” or the target intensity is between 80-100% of maximal heart rate, and “sprint interval training” (SIT) be used for protocols that involve “all -out” or “supramaximal” efforts, in which target intensities correspond to workloads greater than what is required to elicit maximal oxygen uptake or (VO₂peak) (Weston et al., 2014).

人們使用不同的術語來描述各式各樣的間歇訓練方法，產生許多不同的縮寫，在文獻中也缺乏一致性

最近提出了一個分類方案，HIIT這個詞用來描述訓練刺激是”接近最大”或目標強度是介在80%-100%最大心跳率之間的訓練方法，而衝刺間歇訓練(SIT)則是用來描述涉及”全力”或”超大”努力(所需的強度高過誘發最大攝氧量的強度)強度的訓練方法(Weston et al., 2014)

The term "HIIT" will be used exclusively in this review for simplicity, but the interested reader is referred to Weston et al. (2014) for further consideration. Similarly, there is no universal definition of what constitutes “low-volume” interval training, but we have generally considered this to be protocols in which the total amount of intense exercise performed during a training session is ≤10 min, i.e., the summed total duration of the hard efforts, excluding the recovery periods and any warm-up or cool-down (Gibala et al., 2014).

為了單純化，在此篇回顧中只會用HIIT這個詞，如果對更進一步資訊有興趣的讀者可以參考Weston et al. (2014)的研究

同樣的，目前對於什麼構成了”低量”間歇訓練也是沒有統一的定義，但我們一般認為所謂的”低量”指的是在單次訓練課中激烈運動執行的總量≤10分鐘(指的是運動間歇回合的總和時間，休息回合的時間、熱身、緩和都不算在內) (Gibala et al., 2014)

With respect to studies that have examined physiological adaptations to low-volume HIIT, one of the most common protocols employed is the Wingate Test, which involves 30 s of maximal cycling on a specialized ergometer, typically using a braking force or resistance that is equivalent to 7.5% of body mass.

關於那些檢測低量HIIT訓練的生理適應之研究，其中一個最常被使用的方式是Wingate測試(在特殊的測功器上進行30秒的最大強度單車運動，過程中使用的阻力/煞車力量一般約等同於7.5%的體重

The task is extremely demanding, and during a single effort subjects typically generate mean power output values that correspond to ~250-300% of what can be achieved during a standard incremental test to determine (VO₂peak). A single training session lasts ~20-25 min including brief warm-up and cool-down, with subjects typically performing 4-6 Wingate Tests separated by a few minutes of recovery (Burgomaster et al., 2005; Gibala et al., 2006).

這種方式是極度艱苦的，在單次的努力過程中，受測者一般可以產生出相當於在標準的漸增強度測試中最大攝氧量(VO₂peak)被誘發時之250%-300%的平均動力輸出

單一次的訓練課包含短暫熱身與緩和將持續大約20-25分鐘，受測者通常會操作4到6次Wingate測試(中間穿插幾分鐘的恢復  Burgomaster et al., 2005; Gibala et al., 2006)

Another common intervention employed in low-volume HIIT studies is repeated constant-load efforts performed at a high relative (but not all-out) work intensity; for example, ~10 60-s cycling efforts at 100% of the peak power output elicited during a ramp VO₂peak test, or an intensity that elicits ~90% of maximal heart rate, interspersed with a similar amount of recovery between efforts (Little et al., 2010). An overview of some common protocols employed in interval training studies is depicted in Figure 1.

另一個在低量HIIT訓練研究中常被使用的介入是在相對高的做功強度下(但不是全力)進行反覆的恆定負荷努力，舉例來說，大約10回合,運動60秒休息60秒的單車努力，使用的強度是在斜坡VO₂peak測試中，動力輸出峰值被誘發時的100%強度，或是在會誘發大約90%最大心跳率的強度(Little et al., 2010)

一些在間歇訓練研究中常被使用的方式的綜述呈現在下列圖1中

One of the most striking findings from low-volume HIIT studies is the dramatic improvement in exercise capacity during tasks that rely mainly on aerobic energy metabolism, despite the relatively small amount of total exercise training performed (Burgomaster et al., 2005; Gibala et al., 2006; Little et al., 2010).

在低量HIIT研究中其中一個最引人注目的發現是在”主要依賴有氧能量代謝的任務”的運動能力上有戲劇性的提升(儘管總訓練量是相對低的) (Burgomaster et al., 2005; Gibala et al., 2006; Little et al., 2010)

For example, Burgomaster et al. (2005) found that subjects doubled the length of time that exercise could be maintained at a fixed submaximal workload — from ~26 to 51 min during cycling at 80% of pre-training VO₂peak — after only six sessions of Wingate-based HIIT over 2 wk (Figure 2).

舉例來說，Burgomaster發現僅經過2周共6次的Wingate-based HIIT後，受測者在一個固定次最大做功負荷下可持續運動的時間延長為兩倍(在訓練前的80%VO₂peak強度下可維持的運動時間從26分鐘延長到51分鐘)(參考圖2)

The validity of this finding was bolstered by the fact that a control group showed no change in performance when tested 2 wk apart with no training intervention. Subsequent work confirmed that the same HIIT protocol improved performance during tasks that more closely resemble normal athletic competition, including laboratory time trials that simulated cycling races lasting from <2 min to <1 h (Gibala et al., 2006).

這個發現的效度受到了控制組(兩周中都沒有訓練介入)沒有出現表現上的改變之事實所支持

隨後的研究也證實同樣的HIIT訓練方法能增進更相似於正常運動競賽的工作中之表現(包含模擬<2分鐘至<1小時的自行車賽的實驗室時間試煉Gibala et al., 2006)

Obviously, the factors responsible for training-induced improvements in exercise capacity are complex and determined by numerous factors including both physiological (e.g., cardiovascular, ionic, metabolic, neural, respiratory) and psychological attributes (e.g., mood, motivation, perception of effort).

明顯的，因訓練而誘發在運動能力上之提升是受什麼因子所影響是很複雜的，且是由許多因子所決定的(包含生理性的：心血管、離子、代謝、神經、呼吸系統)以及心理性的：心情、動機、自覺費力程度)

The short-term studies cited above (Burgomaster et al., 2005; Gibala et al., 2006; Little et al., 2010) reported no measurable change in VO₂peak after 2 wk of low-volume HIIT, which suggests the improved exercise performance was primarily attributable to peripheral adaptations in skeletal muscle, as considered further below. Some studies have reported improvements in VO₂peak after as little as 2 wk of Wingate-based HIIT, although these were generally conducted on previously sedentary, less fit individuals (Whyte et al., 2010).

上述所引用的短期研究(Burgomaster et al., 2005; Gibala et al., 2006; Little et al., 2010)指出在兩周的低量HIIT訓練後VO2Peak並沒有發生可測量的明顯改變，這意味著運動表現提升主要可歸因於骨骼肌的周邊適應

有些研究指出在僅短短兩周的Wingate-based HIIT後即出現VO₂peak的改善，但是這些研究的受測者通常是先前是坐式生活型態、初始體能較差的(Whyte et al., 2010)

For a comprehensive overview in this regard, the interested reader is referred to several recent reviews including a meta-analysis (Bacon et al., 2013) that have considered VO₂peak trainability in response to HIIT.

關於此事的全面綜述，有興趣的讀者可以參考近期幾個回顧，包含了有深入討論因應HIIT訓練的VO₂peak可訓練性的綜合分析(Bacon et al., 2013)

PHYSIOLOGICAL ADAPTATIONS TO LOW-VOLUME HIIT低量HIIT的生理適應

Similar to traditional endurance or strength training, physiological adaptations to HIIT are highly dependent on the precise nature of the training stimulus, i.e., the frequency, intensity and volume of work performed. However, unlike the other two general categories of exercise training which primarily rely on either oxidative (endurance) or non-oxidative (strength) energy to fuel ATP provision, the bioenergetics of high-intensity exercise can differ markedly depending on the duration and intensity of each interval, the number of intervals performed and the nature and duration of recovery between efforts (Ross & Leveritt, 2001).

與傳統耐力或肌力訓練相似，HIIT的生理適應高度仰賴於訓練刺激的精確本性(我們所執行的訓練頻率、強度、量)

但是，不像前述兩種運動訓練主要仰賴有氧(耐力)或無氧(肌力)能量來保持ATP供應的一般分類，高強度運動的生物能量學會依每個間歇回合的持續時間與強度、進行的間歇回合數與休息回合的型態與持續時間而有明顯的不同(Ross & Leveritt, 2001)

For example, during a single 30-s all-out maximal cycling effort, approximately 20% of total energy provision is derived from oxidative metabolism (Parolin et al., 1999). However, if the exercise bout is repeated three times with four min recovery between bouts, the majority of ATP provision during the final bout is derived from oxidative metabolism (Parolin et al., 1999).

舉例來說，在單次30秒最大自行車努力的運動中，大約20%的總能量提供是來自有氧代謝(Parolin et al., 1999)，但若是運動回合進行三次，中間穿插著4分鐘的恢復回合，在最後一個回合中的大多數ATP能量供應則是來自有氧代謝(Parolin et al., 1999).

The increased contribution from oxidative metabolism during repeated high-intensity efforts is attributable to both an increased rate of oxygen transport and utilization and decreased ability to stimulate substrate phosphorylation through phosphocreatine hydrolysis and glycolysis (Parolin et al., 1999).

在反覆高強度努力中有氧代謝的貢獻提升是歸因於氧氣運輸與利用率的增加與透過磷酸肌酸水解與醣酵解來刺激基質磷酸化的能力下降(Parolin et al., 1999)

High-intensity intermittent exercise is therefore unique because cellular energy during an acute bout or a given training session can be derived primarily from non-oxidative or oxidative metabolism. Consequently, HIIT can elicit a broad range of physiological adaptations and the reader is referred elsewhere for a more comprehensive description of physiological adaptations to HIIT (Buchheit & Laursen, 2013ab; Kubukeli et al., 2002; Ross & Leveritt, 2001). The next sections briefly summarize some of the major metabolic and morphological adaptations to HIIT, again with a focus on recent studies that have examined rapid skeletal muscle remodeling after short-term, low-volume HIIT.

因為在一個急性回合或特定訓練課中的細胞能量可以主要從無氧或有氧代謝中被獲得，高強度間歇訓練於是變的獨特

因此，HIIT可以引起很廣的生理適應範圍，讀者們可以參考其他對HIIT生理適應有更詳細描述的研究(Buchheit & Laursen, 2013ab; Kubukeli et al., 2002; Ross & Leveritt, 2001)

下段將簡短的總結一些HIIT主要的代謝與形態學適應(仍同樣聚焦在近期有檢測在短期低量HIIT訓練後的快速骨骼肌重塑之研究)

Improved “sprint” or high-intensity exercise performance after HIIT is related in part to increases in the maximal activities of enzymes that regulate non-oxidative energy provision (e.g., glycogen phosphorylase, phosphofructokinase), increased muscle buffering capacity and ionic adaptations including increased sodium-potassium ATPase (Na⁺-K⁺-ATPase) content and function (Kubukeli et al., 2002; Ross & Leveritt, 2001).

在HIIT訓練後“衝刺”或高強度運動表現提升部分與以下因素有關(Kubukeli et al., 2002; Ross & Leveritt, 2001)：

1.            酶的最大活性(調節無氧能量供應的酶：糖原磷酸化酶、磷酸果糖激酶)增進

2.            肌肉緩衝能力的改善

3.            包括了鈉鉀幫浦的含量與功能增加的離子適應

In terms of muscle fiber composition, several studies have reported a bidirectional shift to type IIa (I -> IIa <- IIx), similar to the general trend observed after both endurance and strength training, although this is not a universal finding (Kubukeli et al., 2002; Ross & Leveritt, 2001).

在肌纖維組成的方面，許多研究指出二型肌纖維的雙向性轉變(I -> IIa <- IIx)與在耐力與肌力訓練後觀察到的一般趨勢相似，但是這並不是一個普遍的發現(Kubukeli et al., 2002; Ross & Leveritt, 2001)

HIIT does not have a major effect on muscle size, especially compared to heavy resistance training, although a few studies have reported modest but significant hypertrophy of both Type I and Type II fibers after many months of HIIT (Ross & Leveritt, 2001). In this regard, an acute bout of Wingate-based HIIT does not activate signaling pathways within skeletal muscle that are linked to fiber growth/hypertrophy (Gibala et al., 2009).

HIIT對肌肉尺寸並沒有重大影響(尤其是與重的阻力訓練相比時)，但是有些許研究指出在許多個月的HIIT訓練後於一型與二型肌纖維有限但達顯著的肌肉肥大(Ross & Leveritt, 2001)

關於此事，Wingate-based HIIT中的一個劇烈回合並沒有活化骨骼肌中連結肌纖維成長/肥大的訊號路徑(Gibala et al., 2009)

It has long been recognized that HIIT also has the potential to increase muscle oxidative capacity and performance during tasks that mainly rely on aerobic energy metabolism (Saltin and Gollnick, 1983). MacDougall et al. (1998) provided an example of the potency of Wingate-based HIIT when they reported an increased maximal activity of several mitochondrial enzymes after 7 wk of training protocol in which subjects performed 4-10 intervals per day, three times per week. Until recently, little was known regarding the early time course and minimum volume of training necessary to elicit rapid adaptations in skeletal muscle, or the effect of HIIT on substrate metabolism during tasks that mainly rely on aerobic energy provision.

HIIT也有著提升肌肉氧化能力與在主要仰賴有氧能量代謝任務中的表現(Saltin and Gollnick, 1983)是眾所皆知的

MacDougall提供一個Wingate-based HIIT訓練潛力的例子，他表示在七周的訓練後(受測者每天操作4-10個間歇、每周三次)提升了數個粒線體酶的最大活性

直到最近，關於初期的時間進程與能引起骨骼肌中的快速適應所需之最小訓練量，或在主要仰賴有氧能量供應的任務中HIIT對基質代謝的影響仍是鮮為人知的

In a series of studies, we examined rapid adaptations in oxidative energy metabolism and exercise capacity after short-term, Wingate-based HIIT as described above (Burgomaster et al., 2005, 2006, 2007; Gibala et al., 2006). The most unique aspect of this work was the very low training volume, equivalent to only <15 min of very intense exercise or <600 kJ of total work. All studies were performed on healthy college-aged men and women who were habitually active but not engaged in any sort of structured training program.

在一系列的研究中，我們檢驗了在短期、如上述提到(Burgomaster et al., 2005, 2006, 2007; Gibala et al., 2006)的Wingate-based HIIT訓練後之有氧能量代謝與運動能力的快速適應

這個研究最獨特的地方是非常低的訓練量，相當於不超過15分鐘的非常激烈運動(或<600kJ的總做功)

所有的研究都是以健康、大學生年紀、有運動習慣(但沒有參與任何一種有結構性的訓練計劃)的男女性來進行

We have consistently found an increased muscle oxidative capacity (assessed using the maximal activity or protein content of mitochondrial enzymes such as citrate synthase and cytochrome oxidase) ranging from <15-35% after six sessions of HIIT over 2 wk (Burgomaster et al., 2005, 2006, 2007).

我們一致的發現在2周內共六次的HIIT訓練課後(Burgomaster et al., 2005, 2006, 2007)肌肉氧化能力範圍從15~35%的提升(使用如檸檬酸合成酶與細胞色素氧化酶這種粒線體酶的最大活性或蛋白質含量來評估)

Surprisingly, only a few studies had previously compared changes in muscle oxidative capacity after interval versus continuous training in humans, with equivocal results (see references in Gibala et al., 2006). Moreover, the studies that examined muscle oxidative capacity after interval versus continuous exercise training had used a matched-work design in which total work was similar between groups.

有趣的是，先前僅有少數研究對比在人類身上於間歇與持續性訓練後肌肉氧化能力的改變，都有著模糊不清的結果(參考 Gibala et al., 2006)

此外，那些有檢驗對比在間歇訓練與持續性運動訓練後肌肉氧化能力的研究都使用相似總做功量(matched-work)的實驗設計

In our studies, we sought to compare changes in muscle oxidative capacity and exercise performance after low-volume sprint training and traditional high-volume endurance training, such that the two protocols differed markedly in terms of total training volume and time commitment.

在我們的研究中，我們旨在對比於低量衝刺訓練與傳統高量耐力訓練後肌肉中氧化能力與運動表現的改變(而這兩種訓練方式在總訓練量與投入的訓練時間方面而言有明顯的不同)

The sprint protocol consisted of six sessions of brief, repeated “all-out” 30-s cycling efforts, interspersed with a short recovery, over 14 d. The endurance protocol consisted of six sessions of 90–120 min of moderate intensity cycling exercise, with 1–2 d of recovery interspersed between training sessions.

衝刺方案由六次短暫、反覆性的全力30秒、中間穿插短的恢復時間的自行車努力訓練課所組成

耐力方案由六次的90-120分鐘中等強度自行車運動訓練課所組成，在訓練課間穿插1-2天的恢復

As a result, subjects in both groups performed the same number of training sessions on the same days with the same number of recovery days; however, total training time commitment was 2.5 and 10.5 h, respectively, for the sprint and endurance group, and training volume differed by 90% (630 versus 6500 kJ). The two diverse training protocols induced remarkably similar adaptations in exercise performance and skeletal muscle oxidative capacity, as reflected by the maximal activity of cytochrome c oxidase (Figure 3).

結果發現，兩組的受測者進行一樣多次的訓練課、在同一天進行訓練、有著一樣多天的恢復日，但有著不同的投入訓練時間(衝刺組2.5與耐力組10.5小時)，訓練量相差了90%(630kJ與6500kJ)

這兩種不同的訓練方案誘發在運動表現與骨骼肌氧化能力上顯著相似的適應(由細胞色素c氧化酶的最大活性反應出來)(圖三)

In addition to an increased skeletal muscle oxidative capacity after 2 wk of HIIT, we have also detected changes in carbohydrate metabolism that are normally associated with traditional endurance training, including an increased resting glycogen content and reduced rate of glycogen utilization during matched-work exercise (Burgomaster et al., 2006, 2007).

在兩周的HIIT訓練後除了骨骼肌氧化能力的提升之外，我們也觀察到在通常與傳統耐力訓練相關的醣類代謝之改變，包括了休息肝醣儲量的增加與在matched-work運動中肝醣使用率的下降(Burgomaster et al., 2006, 2007)

Selected markers of fatty acid metabolism, including the maximal activity of β-hydroxyacyl- CoA dehydrogenase (HAD) and the muscle contents of fatty acid translocase (FAT/CD36) or plasma membrane associated fatty acid binding protein (FABPpm), were unchanged after our short-term Wingate-based training intervention (Burgomaster et al., 2006, 2007), although we have demonstrated an increased HAD after 6 wk of this type of training.

在我們短期的Wingate-based訓練介入後(Burgomaster et al., 2006, 2007)，選定的脂肪酸代謝標誌物包括了Beta-HADH與肌肉脂肪酸轉位酶 (FAT/CD36)或FABPpm的含量都沒有改變，然而我們在六周此種型態的訓練後發現了HAD的增加

Talanian and co-workers (2007) showed that seven sessions of HIIT over 2 wk increased the maximal activity of HAD, the muscle protein content of FABPpm and whole-body fat oxidation during 60 min of cycling at 65% pre-training VO₂peak.

Talanian與他的研究夥伴指出在兩周共七次HIIT訓練課後即增加HAD的最大活性與肌肉蛋白中的FABPpm含量、以及在訓練前65% VO₂peak強度之60分鐘持續的單車運動過程中全身的脂肪氧化

A major discrepancy between the respective 2-wk training protocols was the nature of the HIIT stimulus. Subjects did not perform all-out sprints in the study by Talanian et al. (2007), however each training session consisted of 10 x 4-min bouts of cycling at ~90% of VO₂peak with 2 min of rest between intervals. Total training time commitment (~5 h) and exercise volume (~3000 kJ) over the 2-wk training period was thus substantially higher than in the studies that employed Wingate-based exercise training (Burgomaster et al., 2006, 2007).

在兩個不同的2周訓練方案之間重大的差異是來自HIIT刺激的本質

在Talanian的研究中，受測者並沒有操作全力衝刺，而是在每次的訓練課中由10回合強度在大約90% VO₂peak進行4分鐘，中間穿插兩分鐘的休息，兩周內投入的總訓練時間(~5 h)與訓練量(~3000 kJ)因此大大的高於其他使用Wingate-based運動訓練的研究(Burgomaster et al., 2006, 2007)

With respect to cardiovascular adaptations, 8 wk of low-volume HIIT has been reported to increase both left ventricular mass and stroke volume (Matsuo et al., 2014). Similar improvements in peripheral vascular structure and function, including popliteal artery distensibility and flow-mediated dilation, were reported after 6 wk of Wingate-based HIIT and traditional moderate-intensity continuous training (Rakobowchuk et al., 2008). A study from a different laboratory that employed the same experimental protocol showed similar improvements in skeletal muscle microvascular density and microvascular enzyme content, despite large differences in total training volume (Cocks et al., 2013). An overview of some of the major physiological adaptations to low-volume HIIT is summarized in Figure 4.

心血管適應的部分，八周低量HIIT訓練已被證實能增加左心室質量與每跳輸出量(Matsuo et al., 2014)

相似的改善也出現在周邊血管的結構與功能(包括膕動脈彈性與血流介導擴張參數)也被發現(在六周的Wingate-based HIIT訓練與傳統中等強度持續性運動後產生的效果類似Rakobowchuk et al., 2008 )

一篇來自不同實驗室的研究使用相同的實驗方案也顯現出儘管在訓練量上有大的差異，於骨骼肌內微血管密度與微血管酶含量也產生相似的改善(Cocks et al., 2013)

一些低量HIIT訓練的主要生理適應綜述總結在圖四

(圖四)在數周的低量HIIT訓練後觀察到的一些主要生理改變概述

心血管系統：增加心臟輸出；降低動脈硬化

骨骼肌肉系統：增加粒線體數量；增加微血管數量

HOW DOES HIIT STIMULATE ADAPTATIONS IN SKELETAL MUSCLE?

HIIT如何刺激在骨骼肌中產生的適應？

The potency of HIIT to elicit rapid changes in skeletal muscle remodeling is no doubt related to its high level of muscle fiber recruitment and potential to stress type II fibers in particular (Saltin & Gollnick, 1983), but the underlying mechanisms are unclear. From a cell-signaling perspective, exercise is typically classified as either “strength” or “endurance,” with short-duration, high-intensity work usually associated with increased skeletal muscle mass, and prolonged, low- to moderate-intensity work associated with increased mitochondrial mass and oxidative enzyme activity (Baar, 2006).

HIIT在誘發在骨骼肌重塑的快速改變潛力與其對高層級的肌纖維的徵招和對二型肌纖維施加壓力的潛力有關係是無庸置疑的，(Saltin & Gollnick, 1983)，但在背後的機制仍不明確

從細胞訊號的觀點來看，運動通常被分類為”肌力”或”耐力”，短持續時間、高強度的運動通常與肌肉質量的增加相關；長時間、低到中等強度的運動通常與增加的粒線體質量與氧化酶活性有關(Baar, 2006)

Indeed, the distinct pathways that regulate either cell growth or mitochondrial biogenesis intersect at a number of points in an inhibitory fashion, resulting in a response that is largely exclusive for one type of exercise or the other (Baar, 2006). 
的確，調節細胞生長或粒線體生源論的不同路徑在一些點以抑制的方式相交，導致特定不同類型的運動訓練間產生的適應會相互排斥(Baar, 2006)

 Until recently, little was known regarding the intracellular signaling events that mediate skeletal muscle remodeling in response to HIIT which, unlike traditional strength training, is not characterized by marked skeletal muscle hypertrophy (Ross & Leveritt, 2001).

直到最近關於因應HIIT訓練細胞內居中調解骨骼肌重塑的信號傳遞事件的理解仍是不多的(但HIIT訓練導致的肌肉適應並不像傳統肌力訓練會造成顯著的骨骼肌肥大Ross & Leveritt, 2001)

Given the oxidative phenotype that is rapidly upregulated by HIIT, it seems likely that metabolic adaptations to this type of exercise could be mediated in part through signaling pathways normally associated with endurance training.

 由HIIT訓練產生氧化表現型快速的向上調節，這種類型的訓練產生的代謝適應很可能部分是透過通常與耐力訓練相關之訊號傳遞路經所調解

Contraction-induced metabolic disturbances activate several kinases and phosphatases involved in signal transduction, including the AMP-activated protein kinase (AMPK) and mitogen-activated protein kinase (MAPK) cascades. These signaling pathways have been shown to play a role in promoting specific coactivators involved in mitochondrial biogenesis and metabolism, including activation of peroxisome-proliferator activated receptor γ coactivator (PGC)-1α, which is regarded as the “master regulator” of mitochondrial biogenesis in muscle (Coffee & Hawley, 2007).

收縮引起的代謝干擾活化了在訊號轉導中涉及的數個激酶與磷酸酶(包含了AMPK、MAPK級聯)

這些信號傳遞路徑已經被證實會在促進特定輔活化因子中扮演角色(參與粒線體生源學與代謝中的輔活化因子，包含了PGC-1α的活化，此輔活化因子被認為是肌肉內粒線體生源學的調節因子Coffee & Hawley, 2007)

It has been demonstrated that Wingate-based HIIT acutely stimulates markers of AMPK and MAPK signaling and increases PGC-1α mRNA by several fold (Gibala et al., 2009; Little et al., 2011), similar to what has been reported after continuous moderate-intensity exercise (Little et al., 2010).

Wingate-based 的HIIT訓練已被證實能產生相似於在持續性中等強度訓練後發現的生理改變(Little et al., 2010) (對AMPK與MAPK訊號傳遞標誌物的強烈刺激與提升PGC-1α mRNA達數倍Gibala et al., 2009; Little et al., 2011)

Also similar to traditional endurance exercise, acute Wingate-based HIIT may activate PGC-1α by increasing its nuclear translocation (Little et al., 2011), and several weeks of HIIT leads to increased PGC-1α protein content (Burgomaster et al., 2008), suggesting that PGC-1α is likely involved in regulating some of the metabolic adaptations to this form of training.

劇烈的Wingate-based HIIT訓練也可能會透過增加PGC-1α自身的核轉位來活化PGC-1α(Little et al., 2011)，數周的HIIT導致PGC-1α蛋白含量增加(Burgomaster et al., 2008)意味著PGC-1α可能也涉及在調節某些因應此類型訓練而產生的代謝適應之中

There is also evidence to show that repeated, transient increases in mRNA in response to successive bouts of HIIT lead to sustained increases in the content of transcription and metabolic proteins, eventually resulting in greater mitochondrial protein content and enzyme activity (Perry et al., 2010).

也有證據指出，因應接二連三的HIIT回合而產生在mRNA反覆性、短暫的提升導致在轉錄與代謝蛋白含量的持續增長，最終導致更多的粒腺體蛋白含量與更高的酶的活性(Perry et al., 2010)

PRACTICAL APPLICATIONS 實際應用

·         HIIT is often dismissed as being only for elite athletes. However, the basic concept of alternating high- and low-intensity periods of exercise can be applied to almost any level of initial fitness.
HIIT經常因為被認為僅適用於菁英運動員的原因而被屏除在訓練計畫內
但是高與低強度的運動時間之變化調整適當的話，HIIT幾乎可以適用於任何體能水平的人

·         As with any form of physical activity, there are potential benefits as well as certain limitations associated with interval training.
如同任何形式的身體活動，間歇訓練有著其潛在益處與特定限制

·         The “pros” include the fact that intervals are a potent training stimulus, and even though the total amount of exercise performed can be quite small, the training can induce adaptations similar to those associated with more prolonged period of continuous moderate-intensity exercise, which makes it relatively time-efficient.
“贊同者”把間歇列入是一個有潛力的訓練刺激，即使總訓練量較少，HIIT訓練也可以引起相似於長時間持續性中強度訓練所產生的適應，從這點來看是十分有時間效益的

·         The “cons” include the uncomfortable feeling of HIIT owing to the relatively intense effort that is required in order to make the training time-efficient, and also the potential greater risk of injury especially if running is performed as compared to less weight-bearing activities such as cycling or swimming.
“反對者”認為由於透過相對激烈的運動來促成訓練時間效益導致HIIT的不舒服感，以及較高的傷害風險(比起單車或游泳，高衝擊性、體重負載的運動尤其有較高風險)

·         While HIIT is effective to improve fitness, there is no magic formula or “one size fits all” approach that is best for everyone, and indeed the best long-term approach is a varied strategy that incorporates strength, endurance and speed sessions as well as flexibility exercises and proper nutrition.
即使HIIT對增進體能十分有效，但卻沒有所謂的對所有人都通用的魔法公式或”萬全之策”，要有長期的的提升與進步，是一個結合了肌力、耐力與速度、柔軟度訓練及適當營養的多樣化策略

SUMMARY總結

Highly-trained endurance athletes have long appreciated the role for HIIT as part of a comprehensive training program. Recent evidence shows that — in young healthy persons of average fitness — intense interval exercise is a time-efficient strategy to stimulate skeletal muscle adaptations comparable to traditional endurance training. As little as six sessions of HIIT over 2 wk, or a total of only <15 min of very intense exercise, can increase skeletal muscle oxidative capacity and improve performance during tasks that rely mainly on aerobic energy metabolism.

受高度訓練的耐力運動員已經長期將HIIT訓練作為全面性的訓練中重要的一部分

最近的證據顯示在一般體能的年輕健康者身上，激烈的間歇運動是刺激肌肉骨骼適應的一個時間效益策略(對比於傳統耐力訓練)

僅經過2周共六次訓練課(或僅少於15分鐘的總激烈運動時間)就可以提升骨骼肌的氧化能力、增進主要仰賴有氧能量供應的任務之表現

These findings should not be interpreted to suggest that low-volume HIIT provides all of the benefits normally associated with traditional endurance training. The duration of the training programs in the published work to date is relatively short (i.e., lasting up to several weeks) and it remains to be determined whether similar adaptations are manifest after many months of low-volume interval and high-volume continuous training.

這個發現不應該被解釋為低量HIIT可以提供通常與傳統耐力訓練相關的所有益處

目前發表的研究中訓練計劃的持續時間都是相對短的(持續數周而已)，對於持續”數個月”的低量間歇與高量持續性訓練後是否會產生相似的適應，仍是需要被檢驗的

It is possible that the time course for physiological adjustments differs between training protocols; the very intense nature of interval training may stimulate rapid changes, whereas the adaptations induced by traditional endurance training may occur more slowly. From an applied practical perspective, it will also be important in future work to identify the optimal combination(s) of training intensity and volume necessary to induce adaptations in a time-efficient manner, given that lack of time remains the most commonly cited barrier to lack of regular exercise participation. 

很有可能生理調整的時間進程會在訓練方式間會有所不同，間歇訓練非常激烈的特性可能會刺激快速的改變，而由傳統耐力訓練引起的適應可能會產生的比較慢

從實際應用的角度來看，未來研究如何辨別必須訓練強度、訓練量來產生有時間效益的最佳化組合是很重要的(考慮到大眾缺乏規律性運動的主因仍是缺乏時間)

野人滴滴咕咕：身體各系統間相互關係，如何讓高強度的訓練不要引起免疫系統錯亂、賀爾蒙失調是需要仔細考慮到自身體能狀況與各種訓練細項的安排，高強度回合持續時間過長、休息回合過短，很可能訓練總量達不到、課表吃不完；"全力”與”能誘發≥85%的攝氧峰值(VO₂peak/VO₂max)”的運動強度對於沒有基礎體能水平的人來說，這種強度可能就像折磨，過程中喘到不行(高心跳)、血乳酸高到爆表，動作控制能力因而受到影響(動作走樣、腦袋當機)、引起賀爾蒙系統與免疫系統拉警報，回合間休息恢復慢、系統的重新調整能力差(長時間高心跳、心肌發炎)，身體能量路徑供能效率差(高比率的無氧能量供應、蛋白質分解造成肝腎負擔)，這麼看下來HIIT訓練即使當次硬是吃完了，覺得很充實很累，完成了一次不得了的成就，檯面下卻是造成腦心肝腎免疫系統、賀爾蒙系統過多的壓力，更別說休息、營養有沒有顧到了，很可能只會在初期出現成績的提升，接著就是長期無法解除的疲勞、肌肉骨骼相關不適，還有最讓人傷心的成績上上下下不穩定、停滯不前的狀況，事實上，就如同本文最後的結論所說，目前已知的HIIT訓練益處大多是從短期的研究中得到，且得到改善的能力也無法取代傳統耐力訓練的所有益處(有些能力是需要透過持續性的耐力訓練來有效提升的)，但這也不代表一般人無法使用HIIT訓練法，只要訓練變數安排得宜就可以將不好的最小化、好的最大化，只可惜要做到這樣，是很有難度的

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