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心兒狂跳,所為何事?

文/耐力網/波肥
20140928:心兒狂跳,所為何事_圖一

【圖】正常心臟中的血液流動模型:藍色為缺氧血,紅色為含氧血。(來源:OpenCurriculum網站

在前一篇文章中,大概探討了各種用來評量自行車訓練方式的優缺點,而關於最受歡迎的方式之一-心率,我摘錄喬福瑞(Joe Friel)書中[1]針對這方面的解釋與探討之原文並以個人的語言來意譯(帶一點超譯),希望能讓大家更明白心率訓練的限制所在。

 

為何不選用心率,速度或感覺來訓練?

WHY NOT HEAR RATE, SPEED OR FEEL? by Joe Friel

心率(Hear Rate)

與大多數運動員的認知相反,心率其實是一個身體的反應結果而不是去推動身體反應的源頭。更具體地說,心率是告訴你現在你的肌肉在做什麼事,而不是讓你的肌肉去更認真地工作,它並非「引擎」,而是「汽油幫浦」。當真正的引擎(肌肉)努力地讓你爬上一個山頭時,你的心臟會抽更多血進入肌肉以讓它繼續工作,「只」用心率來監督訓練就像是用只看著汽車儀表板上的油量表來判斷現在車子開多快,也不是不行,只是本末倒置。

【譯者註:這裡喬福瑞舉的例子並不理想,油量表可以看的出是燃料輸出量,但是心率表指出的是單位時間實際心跳次數(心率),並非心輸出量(心輸出量=心率×心搏量),而心率在穩定訓練條件下可以指出身體的訓練強度,兩者所觀測到的數據本質仍有些差異。】

並不是說心率完全沒有參考價值,你的引擎(肌肉)無法不靠汽油幫浦(你的心臟)來工作,幫浦的負荷程度雖並非直接地與你運動表現相關,卻依然是一個良好的資訊,幫浦若大量地運轉即表示有某些地方正辛苦地工作著。不過一個賽車手不會把汽油幫浦作為運動表現的判斷方式,在競技運動中,引擎才是核心關鍵,而幫浦最多是第二重要。

同理,身為一個自行車騎士,你更應該關注引擎的輸出而並非幫浦的負荷程度。事實上,有違於一般運動員所認知,肌肉才是幾乎所有體能變化所發生的地方,所以你更應該把你的訓練專注在打造更強大的引擎-你的肌肉上,只關心心臟每分鐘把多少血液打進你的肌肉裡並不是最有效的訓練方式。

心率表從1970年代晚期就開始逐漸普及,很有可能你一開始就是使用心率來做為訓練依據,它也的確幫助許多運動員變得更強,不過除了上述的「引擎-幫浦」關係之外,以心率為基本依據的訓練仍有其它極大的限制存在,因為心率很容易受到許多外在因素影響,像是飲食習慣或是受心理上的壓力影響等等(譯者注:比賽當天你可能會像下面這位狂熱粉絲一樣瘋狂)。

ibtDPVSyQ5eC2n.jpg

(來源:TVBS新聞台的網路畫面)

舉一些常見的例子如:賽前喝幾杯咖啡,忘記吃東西結果在運動中血糖不足(相信大家都有這經驗,感覺自己頭昏腳軟像綿花糖一樣),這些時候不管你到底有多拼命,你的心率都會飇升,更何況有人只要一被車陣包圍,就高潮了(此乃人工心率提升法),更別說當騎車騎到一半有東西硬衝進你的耳朵裡、跟你的老闆吵架、或是想到又要把稅金丟到水溝裡了繳給國庫等煩心之事了。撇開這些不說,當你在進行間歇訓練時,心跳的反應也相當不即時,在前幾分鐘你只能用體感去猜你到底開出多大的強度,因此導致你失敗的比賽配速或者是一次糟糕的訓練。在需要穩定配速的比賽中,如計時賽和鐵人賽,你很可能根本沒有發揮你真正的能力水準。

總結以上,最大的限制仍然在於心率不能告訴你到底表現有多好,只能間接地藉由引擎的耗油(氧氣)程度來告訴你引擎多努力,要能真正有效地利用心率,它必需和其它數據相比較,才會顯現它的價值,往後將說明:心率和功率如何做比較, 以及這樣的比較如何輔助你的訓練。

出處:[1]  Friel, Joe. (2012) The Power Meter Hand Book:  A User’s Guide for Cyclists and Triathletes

WHY NOT HEAR RATE, SPEED OR FEEL? by Joe Friel

Contrary to what most athletes believe, heart rate is reactive, not proactive. In other words, it responds to what the muscles are doing. It does not cause the muscles to work any harder. It’s not the “engine”—it’s simply the “fuel pump.” When the engine (muscles) works harder going up a hill, the heart responds by pumping more blood to help the muscles keep going. Training based only on heart rate is like using the fuel gauge on your car to determine how fast you’re driving. That can be done, but it’s “bass-ackwards.”

Now, don’t get me wrong. The fuel pump (your heart) is quite valuable to performance. The engine (your muscles) couldn’t work without it. How hard the pump is working is good information to know as it’s indirectly related to performance. If the engine is demanding lots of fuel, then something hard is probably happening. So the pump had better be capable of delivering. But no race-car driver would use the fuel pump as a way of determining performance. The engine is at the center of fast car racing. The fuel pump is of secondary importance at best.

In the same way, we as bike racers are better off looking at what the engine is producing rather than at how hard the pump is working. In fact, your training should be focused on building the engine—your muscles. Contrary to what athletes who use heart rate monitors believe, muscle is where nearly all fitness changes take place. Focusing only on the rate at which blood is pumped to the muscles is not the most effective way to train.

More than likely you have been using a heart rate monitor ever since you started in your sport. They’ve been around since the late 1970s, so athletes have become quite used to them. And they’ve measurably helped to improve performance for many. But other than the pump-engine relationship I described above, there are still significant limitations to heart rate–based training. Heart rate is affected by “outside” forces, such as diet, race-day excitement, and psychological stress. For example, caffeinated drinks and even a shot of sugar can cause heart rate to rise regardless of how hard you are pushing yourself. Simply being around other riders, especially in a race, will also result in an artificially high heart rate. And even the stuff that goes on between your ears—an argument with the boss, tax time, and other worries—has an effect on heart rate that is unrelated to your riding intensity. Furthermore, in training heart rate is slow to respond when you are doing intervals, so during the first few minutes of each interval you are forced to guess how hard to go. All of this sets you up for poor workout and race pacing. It could very well be the reason you’ve not done as well as you are capable of doing, especially in steady-paced racing such as time trials and triathlons.

Still, the greatest limitation is that heart rate doesn’t tell you anything about how you are performing. It only tells you, indirectly, how hard the engine is working based on the engine’s demand for fuel and oxygen. To be truly effective, heart rate must be compared with something else. I will show you inChapter 6 how power and heart rate can be compared and how the benefits of this relationship can be useful for your training.

心兒狂跳,就是疾走?

從喬福瑞的觀點中,可以明白他在自行車訓練上對心率訓練限制的看法是:「想要提昇自行車訓練的效率,你最好要有兩項以上的監測方式」。除非你是一個敏銳的藝術型運動員(完全體感訓練者,需要天分),因為人的身體是個複雜的裝置,單一的監測方式容易讓我們見樹不見林,很可能會因此看不清自己欠缺的部分而在訓練上搞錯方向,多走冤枉路,抑或是在比賽策略失當。根據喬福瑞提出的「引擎-幫浦」模型,我舉個例子可能可以幫助大家更明白:曾經我有一次出差中,每天中午因用餐都會經過停車場,我注意到有一台車子都停在固定的位置,引擎轟轟轟地轉著,車主在車內把駕駛座打平,躺在裡面午休,每一天的中午都是如此,當一台車子正在狂耗油的時候,不見得是它在狂飇中,也有可能是冷氣開很強啊!相信這樣的經驗大家可能都有過,只要在炎炎夏日的七八月參加一場七八點才開跑的馬拉松賽就能體驗到了。

最後做個總結,單一的心率數字可能表示的資訊並不很多,多少有點霧裡看花,只有在「比較」之後,它的價值才能真正顯現,所幸現在科技很發達,幾乎都是一隻錶內包山又包海,只要買一個錶頭加上對應的感應器,就能夠一次看到多種資訊。不過這麼多資訊又要怎麼比較和怎麼判讀呢?欲知詳情,請待下回分曉!

 

耐力網LOGO(160象素寬)作者:波肥(曾奕穎)/編輯:徐國峰

圖片來源:Triathlon Science

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