Zone 2訓練：你需要知道的事情

Zone 2 Training: What You Need to Know

10.5297/ser.202309_25(3).0000

(Andrew Nicholls)；郭家驊(Chia-Hua Kuo)

大專體育學刊

25卷3期（2023 / 09 / 30）

i - vi

繁體中文;英文

壹、前言。Zone 2訓練已成為健身和跑步界的熱門話題，對於資深運動員和新手來說都如此。但Zone 2訓練究竟是什麼呢？簡單來說，它是一種在相對低強度下進行的長時間運動訓練，通常被描述為「舒適的挑戰」。想像一下以一種你能夠輕鬆交談而不喘的慢跑步伐—這就是Zone 2訓練的本質。Zone 2訓練的概念源於耐力運動，例如自行車、鐵人三項和馬拉松等領域（Esteve-Lanao et al., 2017）。運動員深入研究了「訓練強度分配」（training intensity distribution, TID）的概念，在他們的訓練計畫中策略性地融入不同的訓練強度。為了更容易理解，運動科學家將訓練強度粗分為低中高區域（Zone 1到Zone 3），便利起見通常使用心率作為一個指標，因為大多數人無法進行高級評估，例如血乳酸和氧氣消耗速度。Zone 1即第一心率區域是低於乳酸閾值的運動強度，可用於運動員平時作暖身或動態恢復（最大心率的50%～80%）。Zone 2第二心率區域介於乳酸閾值和無氧閾值之間（最大心率的80%～90%），而Zone 3第三心率區域則高於無氧閾值（最大心率的90%以上；Seiler & Kjerland, 2006; Sylta et al., 2014）。這些區域比例多寡有助於運動員和教練追蹤他們過去的訓練強度，作為未來重新調整這三區訓練比例分配以提高體能表現的參考。隨著可穿戴設備例如運動手錶的出現，運動員可以輕鬆監控他們在每個訓練區域中所花費的時間比重，使其成為他們改善訓練的寶貴工具。將訓練強度分為不同的區域，提供了一種從訓練經驗中獲得最大體能提升效益的簡便方法。這些不同的區域是基於乳酸閾值的概念而來的。在過去學術研究文獻中，Zone 1是強度較低的區域，一直持續到第一通氣閾值（first ventilator threshold, Vt1），在這裡乳酸水平保持在小於（或等於）2 mmol/L。在這個水平上，與休息狀態接近，脂肪氧化提供較高比例的能量，您可以繼續訓練數小時。在超過這個強度水平後，您進入乳酸閾值區域，有時會稱為無氧閾值，定義為Vt1和呼吸代償閾值（respiratory compensation threshold [RCT]，也是第二通氣閾值[second ventilator threshold, Vt2]）之間。研究認為，這個區域是「中等」強度，表明對醣類能量的消耗開始增加，乳酸產生，更多地依賴肝醣（糖原）來提供能量。訓練有素的運動員可以保持這種狀態約1小時。最後一個區域（Zone 3）位於此之上，您在這個區域處於接近最大的努力水平，大多數人只能堅持幾分鐘，而菁英運動員則可以堅持20～30分鐘。在Zone 3，您使用肝醣（糖原）和乳酸作為主要能量來源，這被標記為「高」強度，耗竭的時間即將來臨。在大多數健身媒體和應用中，例如：Strava應用程式、Oura戒指和Whoop手環，將這三個區域進一步細分為Zone 1和Zone 2（Vt1之前的「主動恢復」和「耐力」），Zone 3和Zone 4（Vt1～Vt2～乳酸閾值訓練，也稱為「速度」和「閾值」），Zone 5（「最大攝氧量」），還有一些使用Zone 6和Zone 7（最大無氧閾值）。當閱讀媒體文獻時，這可能會讓人感到困惑，因為一些媒體所謂Zone 2訓練（耐力訓練）的常見用法有可能是學術論文中的Zone 1。本文將依學術研究的慣例僅將運動強度分Zones 1～3，其中Zone 2即為常見的長時間耐力訓練，達到Vt1以上的水平。貳、Zone2訓練的關鍵問題。一、Zone 2訓練能有效減脂和增肌嗎？簡短的答案是「不能」。「燃脂」與「減脂」不能混為一談（Harris & Kuo, 2021）。燃脂也不是減脂的唯一途徑。運動強度高時因組織損傷多，人體細胞再生需求增加。最近有研究證實來自脂肪細胞的脂肪酸是細胞再生建構膜的重要資源，與免疫細胞一起清除損傷組織，阻斷脂肪細胞產生脂肪酸將延後復原時間（Merrick & Seale, 2020）。運動過程脂肪細胞將釋放脂肪酸進入血液，血液脂肪酸濃度上升程度與隨強度增加正比關係，但全身燃脂卻沒有增加，顯然是將脂肪酸保留給細胞修復與再生使用。用可信賴的體脂肪測量工具（雙能X光[dual-energy X ray absorptiometry, DEXA]與核磁共振[magnetic resonance imaging, MRI]，排除生物阻抗分析[bioelectrical impedance analysis, BIA]）來看，Zone 2類型的訓練強度對減脂幫助不大，明顯低於Zone 3類型的訓練（Vissers et al., 2013）。另外，平時只做Zone 2訓練不利增肌，增肌仍仰賴高強度運動。二、Zone 2訓練是否有助於抗衰老？同樣的答案是「不是最好的」。如果將Zone 2和Zone 3的10分鐘自行車訓練強度進行比較，只有後者才看得到減少人體肌肉細胞衰老的效應，Zone 2的強度毫無減少肌肉細胞衰老的效果（Jean et al., 2023）。另外，長期的人體試驗指出，將強度提高到激烈水平（屬於Zone3類型的運動）在提高未來存活率上（50歲以上）比中強度更明顯（Byberg et al., 2009），強度才是抗老化的關鍵。總之，Zone 2訓練應被視為強度較高的訓練計畫的輔助部分，可以作為運動員的輔助運動或動態恢復。儘管它有其優點，但絕不是減少脂肪或抗衰老的最有效方法。運動員和健身愛好者可自行調整各種訓練強度的比例（Zone 1:Zone 2:Zone 3），來實現他們的特定目標來優化體能。

What Is Zone 2 Training? Zone 2 training has become a hot topic in the world of fitness and running for both seasoned athletes and newcomers. But what exactly is Zone 2 training? In simple terms, it's a form of exercise that involves working out at a relatively low intensity for an extended period, often described as a "comfortable challenge." Imagine jogging at a pace where you can hold a conversation without gasping for breath-that's the essence of Zone 2. The concept of Zone 2 training is originated in the realm of endurance sports such as cycling, triathlons, and marathons (Esteve-Lanao et al., 2017). Athletes have delved into the idea of "training intensity distribution (TID)" to optimize their athletic performance. This involves strategically incorporating different exercise intensities into their training routines. To make it more accessible, sports scientists have divided exercise intensity into distinct zones, often using heart rate as a gauge since most individuals don't have access to advanced assessments like blood lactate and oxygen consumption. Zone 1 intensity is considered dynamic recovery below the lactate threshold (50%-80% of maximum heart rate). Zone 2 intensity falls between the lactate threshold and the anaerobic threshold (80%-90% of maximum heart rate), while Zone 3 intensity is above the anaerobic threshold (above 90% of maximum heart rate; Seiler & Kjerland, 2006; Sylta et al., 2014). These zones help athletes and coaches track their training intensity and make necessary adjustments for better performance. With the advent of wearable devices like sports watches, athletes can easily monitor the time they spend in each of these training zones, making it a valuable tool in improving their training. In most fitness media and applications [APPs] like Strava, Oura ring and Whoop band, these three zones are further split into Zone 1 and Zone 2 (pre-first ventilatory threshold [Vt1] "active recovery" and "endurance"), Zone 3 and Zone 4 (Vt1-second ventilatory threshold [Vt2]-lactate threshold training, also called "tempo" and "threshold"), Zone 5 ("maximal oxygen uptake [VO_(2max)]") and some use Zone 6 and Zone 7 (maximal anaerobic). This may be confusing when reading the literature, as the common use of Zone 2 training (endurance conditioning) is actually Zone 1 in the academic literatures. The remainder of this article will refer to the common use of Zone 2 as endurance training up to a level of the Vt1. Key Questions Surrounding Zone 2 Training. 1. Is Zone 2 the Most Effective Intensity for Fat Loss and Muscle Gain? The short answer is "No." Many people confuse fat burning (fatty acid oxidation) with fat loss (Harris & Kuo, 2021). Exercise increases plasma fatty acid levels from hydrolyzing triglyceride (lipolysis) in an intensity-dependent manner-that is, the higher the intensity, the more fatty acids are released into circulation. However, the 24-hr fat burning rate (fatty acid oxidation) remains unchanged during and after exercise regardless of the intensity. You may wonder why there is a need for extra fatty acids entering circulation after high intensity exercise when it is not being oxidized to carbon dioxide? Recent studies have found that fatty acids released from fat cells are used for tissue damage repair and building new cells. Rebuilding cell membranes demands fatty acid. Blocking this process decreases wound healing (Merrick & Seale, 2020). Therefore, the higher levels of fatty acids released during high intensity exercise are more likely preserved for tissue repair and not for energy production. Based on studies employing reliable fat assessment instruments (Vissers et al., 2013), training at Zone 2 intensity is not very helpful for fat loss, despite fatty acid oxidation being greater than Zone 3 intensity. Additionally, Zone 2 training alone is not beneficial for muscle mass gain. Only high intensity workouts possess significant tissue-damage effects to elicit muscle mass gain. 2. Can Zone 2 Exercise Contribute to Anti-Aging Benefits? Again, the answer is "Not the best." If you compare cycling exercise at the intensity of Zone 2 and Zone 3, only the latter produces a senolytic effect (clearance of old or weak cells; Jean et al., 2023), which has the best potential anti-aging benefits. Additionally, studies have shown that increasing exercise intensity to a vigorous level can lower mortality rates for individuals (aged > 50 years; Byberg et al., 2009). This reminds us-we also need high intensity zone training as part of our health regimen. In conclusion, Zone 2 exercise should be viewed as a complementary component of an intensive training regimen, most suited for endurance athletes. While it has its merits for fitness, it may not be the most effective approach for fat loss or anti-aging benefits. Athletes and fitness enthusiasts should consider incorporating a variety of training intensities to achieve their specific goals and optimize their performance.