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What Is Exercise Intensity?
by Drew Baye on August 26, 2014 in Exercise
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Since there seems to be a lot of confusion over the meaning of intensity in the context of exercise, fueled in large part by marketing bullshit, I’m going to explain it in a way that should make it crystal clear to a retarded goat (yes, I’m paraphrasing Arthur Jones).
First, keep in mind intensity is not a thing in and of itself, but a measure of something. When we’re talking about “intensity” in the context of exercise we’re really talking about the measure of things like relative effort, relative load, heart rate elevation, etc., and rather than just saying “intensity” we really ought to be more specific, saying “intensity of effort” or “intensity of load”.
In High Intensity Training (HIT) “intensity” is usually used to mean intensity of effort, or how hard you are working relative to how hard you are capable of working at the moment, and that is what I usually mean when I say or write “intensity”. For example, if you perform an exercise using a resistance that is eighty percent of your one repetition maximum your intensity of effort at the beginning of the exercise will be eighty percent, but as you fatigue the resistance becomes an increasing percentage of your decreasing strength, until your strength has been reduced to the point where it equals the resistance and your intensity of effort is one hundred percent.
Intensity of effort is often criticized as being imprecise, since it is not accurately measurable during exercise except at the point of momentary muscular failure, but since relative effort appears to be the most important factor for stimulating improvements in muscular strength and size it is the most relevant, and most useful (1).
Most of the rest of the fitness industry uses “intensity” to mean intensity of load, the percentage of your one repetition maximum used for an exercise. There are several problems with this, however, including problems with accurately testing one repetition maximums. Although all types of exercise intensity are meant as a measure of how hard you are working during an exercise there are numerous factors which affect exercise difficulty and it is possible to work easier or harder with the same percentage of your one rep max by changing one or more of these factors, such as whether the exercise is performed to the point of momentary muscular failure. Also, as long as an exercise is performed to the point of momentary muscular failure (maximum intensity of effort) most people do not perceive any difference in difficulty using different relative loads (2) or even perceive greater difficulty with lighter loads (3).
Regardless of the relative load used, if you are not training to momentary muscular failure you are not working as intensely as possible.
It could be argued that despite these problems intensity of load can be used to estimate the average intensity of effort of an exercise. Assuming a relatively constant rate of fatigue, and assuming the exercise is stopped immediately after momentary muscular failure occurs, the average intensity of effort during the exercise would be halfway between the percentage of one-rep max used and one hundred percent.
This is a lot of assumptions, however, and several things can throw this off. Fatigue during exercise is the result of numerous factors, which can vary depending on protocol, and probably does not occur at a constant rate. When training people on Ken Hutchins’ iMachines with real-time force measurement and feedback (displayed as a line on a graph) it was not unusual for the rate of fatigue to increase towards the end of the exercise. Also, if you continue to contract isometrically for several seconds after achieving concentric momentary muscular failure you increase the relative time spent working at maximum intensity of effort, increasing the average (and I suspect this may be a factor in the increased effectiveness of several advanced high intensity training methods as well as the reason they seem to make greater demands on recovery).
In addition to all these problems there appears to be little difference on average in muscular strength and size increases with different relative loads and repetition ranges as long as exercises are performed to momentary muscular failure, which throws a huge wrench into the claims that load equals intensity, or that ultra-heavy ultra-brief sets are the way to go (1, 4).
The biggest problem with using load to define intensity is thinking that mechanical definitions of work and power or force or load over time accurately describe what is happening in the muscles during exercise.
This is easy to disprove, and Arthur Jones wrote about this decades ago in The Metabolic Cost of Negative Work,
A great deal of confusion exists on this point because of attempts to compare metabolic work with mechanical work, and, secondly, because of a failure to consider several related factors.
By definition, work require movement… no movement means no work; and while this is undoubtedly true in regard to mechanical work, it certain is not true in relation to metabolic work.
Muscles produce force, and it is easily possible for a muscle to produce a high level of force without producing movement; logically, it appears that the metabolic cost of muscular force production would be related to the level of force produced and the time that the force is maintained… rather than the amount of mechanical work performed.
If, for example, a 100-pound barbell is held motionless at the halfway position of a curling exercise, then the muscles will be required to produce a certain level of force to prevent the downward movement of the barbell. Providing that force will certainly entail metabolic cost… yet no work is involved.
Slowly, curling a 100-pound barbell also requires a greater metabolic cost than curling the same barbell at a more rapid pace; even though the amount of mechanical work involved is exactly the same in both cases.
Many other examples could be given to illustrate the same point, but it should now be obvious that attempts to relate metabolic cost to mechanical work are doomed to failure.. there is no meaningful relationship. We must have another standard for comparison.
The only meaningful standard, I can think of is force/time… the amount of force produced by the muscles multiplied by the time that the force is maintained.
Force multiplied by time is a much better measure of exercise difficulty than mechanical work, but still flawed since it is possible to have the exact same force output and duration and even the same mechanical work and still have different levels of difficulty if the repetition cadence, range of motion, or other factors are varied. For example, if you perform ten repetitions of an exercise each taking eight seconds with the same load, over the same range of motion your mechanical work, power, and force multiplied by time would be the same, but the difficulty will be different if you lift in two seconds and lower in six, lift in four and lower in four, or lift in six and lower in two since your muscles are stronger and fatigue more slowly when lowering than lifting and since the force your muscles are capable of producing concentrically varies with contraction velocity.
Differences in strength and resistance curves complicate this further. Although it is possible to get a resistance curve that very closely approximates your strength curve using machines with well designed cams with adjustable timing like Ken Hutchins “Alligator” machines or lifting weights with correct body positioning and movement during some free weight exercises, it is impossible to match your strength perfectly over the full range of an exercise using weight-based machines (the accommodating resistance of motorized machines is a different story, although it has it’s problems, too). Because of this, there will be portions of the range of motion that are harder, and portions that are easier, and depending on the amount of time you spend in each during both the positive and negative the exercise may be more or less difficult. For example, during most compound pushing movements the target muscles are working against a much larger lever at the start point than the end point. Performing the lower turnaround very slowly, or even holding briefly at the start point makes an exercise more difficult, while performing the upper turnaround any more slowly than necessary or holding there makes an exercise easier.
For example, imagine if you were to perform two sets of barbell squats with the same weight, same number of repetitions, and same cadence, one in the top half of your range of motion, one in the bottom. The force multiplied by time and mechanical work would be the same, but the set performed in only the bottom half of your range of motion would be much harder.
This is because the force you produce when contracting against the resistance is the product of both muscular force and leverage. As your muscles contract and cause your bones to move their angle of pull and leverage changes, so the same amount of force applied to a machine or weight through those bony levers can require more or less muscular force input depending on the part of the range of motion you are in. This is the reason some exercises are harder in some portions of the range of motion and easier in others, the reason you are capable of holding much more weight at or near lockout on pushing exercises, and the reason that load multiplied by time is not a valid measure of exercise difficulty.
It is the reason leg pressing something as heavy as a small car over a range of motion of only a few in
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ホームブログ無料ダウンロード本をヒットします。訓練や相談UXS の複数の運動の駅法的です運動強度とは何ですか。ドリューベイズ 2014 年 8 月 26 日運動の上でXWelcome Googler!このページを便利にすると、場合は、当社のメーリング リストを購読無料の更新のトピックこの。あなたのメール アドレスを入力してください。 遅らせられたヤギを透明なする必要がある方法でそれを説明するつもりがマーケティングのでたらめ、大きい部分で支え、運動のコンテキストにおける強度の意味上の混乱の多くをするようであるので (はい、私はパラフレーズ Arthur Jones)。まず、心の強さには自体が何かの測定のことではないです。とき本当に相対的な努力、相対負荷、心拍数上昇、等のような事の測定について話してして「強さ」我々 は本当に具体的にすべきと言っているだけではなく「努力の強度」を言って練習のコンテキストで"強さ"や"負荷の強度"について話しています。高強度トレーニング (ヒット) が「強度」は通常使用では、またはどのように一生懸命努力の強度を意味するどのようにハードあなたが現時点での作業の能力が基準にしているとそれは「強さ」を言う書いたりするとき私が通常意味。たとえばのあなたの 1 つの繰り返しの最大の 80% は、抵抗を使用して運動を行う運動の先頭に努力のあなたの強度 80% になりますが、抵抗を疲労となるあなたの減少の強さの増加割合抵抗に等しいそれの努力あなたの強度が 100 パーセント ポイント削減されていますあなたの強さまで。それはないので正確に測定可能な運動中に瞬間的な筋肉の障害の時点で相対以来努力が表示されますの最も重要な要因であることを除いて努力の強度は、不正確なものとしてしばしば批判されて筋肉の強さとそれが最も関連性の高い、最も役に立つ (1) 大きさの改善を刺激すること。フィットネス業界の残りの部分のほとんどは、負荷、運動のために使用、1 つの繰り返しの最大の割合の強さを意味するのに「強さ」を使用します。いくつかの問題、ただし、正確に 1 つの繰り返しの最大値をテストの問題などがあります。対策として運動強度のすべてのタイプのものですが、運動中に作業しているどのようにハードの行使難易度に影響を与える多数の要因があるし、それ瞬間的な筋肉の障害のポイントに運動を実行するかどうかなど、これらの要因の 1 つ以上を変更する困難あなたの一担当者の最大の割合が同じかより簡単に作業することが可能。また、瞬間的な筋肉の障害 (努力の最大強度) のポイントに運動が実行されます限り、ほとんどの人々 を知覚しない難易度別相対荷重 (2) を使用しての違いまたはも負荷が軽い (3) の大きい難しさを認識。相対的な負荷に関係なく使用、瞬間的な筋肉の障害として可能な限り激しく作業していない場合にトレーニングできない場合。これらの問題にもかかわらず負荷の強度を運動の努力の平均強度を推定する使用することができると言えるでしょう。疲労、比較的一定率を仮定して、運動が瞬間的な筋肉の障害が発生した後にすぐに停止するいると仮定すると、運動中に努力の平均強度は一担当者最大使用率 100% の中間になります。しかし、これは仮定の多く、いくつかはにこれを投げることができます。運動時の疲労は、プロトコルによって異なることが一定の割合で発生しませんおそらく多数の要因の結果です。リアルタイムのケンハッチンス ' iMachines の訓練の人々 を強制的に測定とフィードバック (グラフ上の線として表示されます) とき、それは運動の終わりに向かって増加する疲労率の異常なでした。また、数秒用尺の契約を続行する平均増加する努力の最大強度で費やされた相対時間の増加同心の瞬間的な筋肉の障害を達成した後 (と回復の大きい要求をするように見える彼らの理由と同様に、いくつかの先進的な高強度のトレーニング方法の増加効果の要因になる可能性がありますこれと思う)。すべてのこれらの問題に加えて筋力の平均で少し違いがあるし、練習は負荷に等しい強度の要求に巨大なレンチをスローすると、瞬間的な筋肉の障害に実行される限り、異なる相対荷重や繰り返しの範囲との増加のサイズが表示されますまたは超重超簡単なセットに行く方法である (1, 4)。負荷を使用した強度の定義の最大の問題は、思考機械仕事および力または力または負荷の定義時間をかけて運動中筋肉に起こって正確に記述します。これは反証、やすいと Arthur ジョーンズはこの十年の前に負の仕事の代謝コストについて書いた機械的な仕事と代謝の仕事を比較する試みのためこの点で大いに混乱が存在して、第二に、考慮する失敗のためのいくつかの関連要因。定義では、動きで必要な作業は動きは仕事がないことを意味これは機械的な仕事に関して間違いなく事実、特定だと代謝の仕事に関連して true。筋肉を作り出す力と筋肉運動を伴わず力の高レベルを生成するは可能です。論理的には、筋肉の力の生産の代謝コストが生産力と機械的な仕事の量が実行されるよりもむしろ... 力が保持される時間のレベルに関連しているようであります。たとえば、100 ポンドのバーベル カーリング運動の中間の位置で動かずに開催される場合、筋肉はバーベルの下方への移動を防ぐために力の特定のレベルを生成する必要になります。力、代謝コストを伴う確かにまだ仕事が関与していることを提供します。ゆっくりと、100 ポンドのバーベルをカーリングもカーリングより急速で同じバーベルよりも大きな代謝コストが必要です。にもかかわらず、機械的作業の量は、同じでも。Many other examples could be given to illustrate the same point, but it should now be obvious that attempts to relate metabolic cost to mechanical work are doomed to failure.. there is no meaningful relationship. We must have another standard for comparison.The only meaningful standard, I can think of is force/time… the amount of force produced by the muscles multiplied by the time that the force is maintained.Force multiplied by time is a much better measure of exercise difficulty than mechanical work, but still flawed since it is possible to have the exact same force output and duration and even the same mechanical work and still have different levels of difficulty if the repetition cadence, range of motion, or other factors are varied. For example, if you perform ten repetitions of an exercise each taking eight seconds with the same load, over the same range of motion your mechanical work, power, and force multiplied by time would be the same, but the difficulty will be different if you lift in two seconds and lower in six, lift in four and lower in four, or lift in six and lower in two since your muscles are stronger and fatigue more slowly when lowering than lifting and since the force your muscles are capable of producing concentrically varies with contraction velocity.Differences in strength and resistance curves complicate this further. Although it is possible to get a resistance curve that very closely approximates your strength curve using machines with well designed cams with adjustable timing like Ken Hutchins “Alligator” machines or lifting weights with correct body positioning and movement during some free weight exercises, it is impossible to match your strength perfectly over the full range of an exercise using weight-based machines (the accommodating resistance of motorized machines is a different story, although it has it’s problems, too). Because of this, there will be portions of the range of motion that are harder, and portions that are easier, and depending on the amount of time you spend in each during both the positive and negative the exercise may be more or less difficult. For example, during most compound pushing movements the target muscles are working against a much larger lever at the start point than the end point. Performing the lower turnaround very slowly, or even holding briefly at the start point makes an exercise more difficult, while performing the upper turnaround any more slowly than necessary or holding there makes an exercise easier.For example, imagine if you were to perform two sets of barbell squats with the same weight, same number of repetitions, and same cadence, one in the top half of your range of motion, one in the bottom. The force multiplied by time and mechanical work would be the same, but the set performed in only the bottom half of your range of motion would be much harder.This is because the force you produce when contracting against the resistance is the product of both muscular force and leverage. As your muscles contract and cause your bones to move their angle of pull and leverage changes, so the same amount of force applied to a machine or weight through those bony levers can require more or less muscular force input depending on the part of the range of motion you are in. This is the reason some exercises are harder in some portions of the range of motion and easier in others, the reason you are capable of holding much more weight at or near lockout on pushing exercises, and the reason that load multiplied by time is not a valid measure of exercise difficulty.It is the reason leg pressing something as heavy as a small car over a range of motion of only a few in
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