馬の足の熱が必ずしも悪いことではない理由

温めが効果的な場合と、逆に害になる場合を理解しましょう。

特に運動中にブーツやバンテージを使用する際、馬の脚が過度に熱くなるリスクについて、関心が高まっています。こうした意識が高まっていることは、非常に良いことです。2008年当時、Equilibriumはブーツ素材の通気性や保温性を試験することをいち早く提唱した企業の一つであり、それ以来、この分野の研究は大きく進展しています。

しかし、ここで重要な事実があります。

馬の脚に熱がこもることが、必ずしも有害なわけではありません。実際、時には効果的なこともあります。

危険が生じるのは、熱が 過剰になり、 運動中や運動後に閉じ込められ、 自然な冷却を妨げる場合、 または、発生したばかりの新しい怪我に適用した場合です。

Why Tendons Warm Up During Exercise

Tendons and ligaments act as energy-storing springs. With every stride, they stretch, store energy, and recoil to help power movement. This elastic work naturally generates heat, which can improve how tendons function because:

  • Warm tendons become more elastic
  • Soft tissues absorb and release energy more effectively
  • Stiffness is reduced

In short: warmth improves performance and reduces injury risk.

A key point to understand: Equine tendons have a poor blood supply, meaning they can’t release heat as quickly as muscles. Their main cooling mechanism comes from:

  • Airflow over the limb
  • Evaporative cooling from skin moisture (i.e. sweat)

Because of this, heat naturally increases—and that’s normal.

When Heat Becomes a Problem: Exercise + Insulation

Problems arise when exercise generates significant heat while boots or wraps restrict airflow and act like insulation. This can push tendon temperatures into ranges considered stressful for tendon cells.

What the science says

  • Tendon temperatures during galloping can reach around 45°C, based on biomechanical modelling of energy-storing tendons. Wilson & Goodship, 1994
  • Tendon fibroblast survival decreases when exposed to temperatures in the low- to mid-40s°C, suggesting heat may contribute to tendon degeneration if sustained. Birch, Wilson & Goodship, 1997
  • Leg protection (boots, wraps, bandages) increases skin temperature compared to bare limbs during and after exercise. This has been shown for multiple materials, including neoprene and polo wraps.
    Schramel et al., 2014, Brock & Spooner, 2021, Dailey et al., 2023

In other words: Heat isn’t the enemy—heat that cannot escape is.

Insulating boots can delay cooling even after exercise stops, prolonging the period where tendon temperatures remain high. This is why it is important to remove boots immediately after exercise.

Why boots can contribute to the problem:

Most boots reduce:

  • Airflow
  • Evaporative cooling
  • Direct heat release

This creates what is essentially a “thermal wrap” around a structure that already struggles to cool itself.
This is why “heat” is generally a problem during exercise—especially intense or prolonged work.

What About Stable Boots and Turnout Boots?

Many owners now ask whether stable boots or turnout boots also cause overheating. Fortunately, the risk is significantly lower in these environments—because tendon heat largely depends on how hard the horse is working.

1. In the Stable

Horses in stables spend long periods standing still. Without mechanical loading, tendons generate minimal heat. In cold weather, the lower limbs often become cold due to naturally reduced circulation, and some horses even develop “filled legs” (lymphatic pooling).

In these cases, gentle warmth from breathable chaps or stable boots can be beneficial, helping:

  • comfort
  • circulation
  • mobility when first moving off

Stable boots should still be checked daily, but the risk of tendon overheating is low.

2. In the Field

Turnout during the winter generally involves:

  • grazing
  • walking
  • short bursts of play
  • long periods of low activity

These activities produce much less tendon heat than ridden exercise. The risk of overheating is minimal, and in winter, some horses are actually more comfortable with additional warmth.

Should You Worry About Sweat Under Boots?

Heat isn’t the only concern. Moisture trapped under boots—whether from sweat, rain, or mud—can soften and weaken the skin.

In human dermatology, this is well understood:

The principles are directly relevant to horses:

Warm, damp skin under boots is more prone to rubbing, irritation, and minor infections.

This doesn’t mean boots are unsafe—but it reinforces the importance of choosing breathable materials and checking the skin daily. It’s also important to note that any boots used should be dry too – so quick drying materials and having a spare pair to swap to could be key in maintaining skin health.

飼い主は、オーバーヒートと皮膚の健康について、実際にいつ心配すべきでしょうか？

リスクの高い状況：

  • 激しい運動や長時間の乗馬
  • 運動直後
  • 暑い天候
  • 厚手で通気性のないブーツ（例：無地のネオプレン製）
  • 暖房の効いた室内で長時間装着したままのブーツ
  • 汗、雨、泥でびしょ濡れになったブーツ
  • 皮膚の敏感さがわかっている馬

リスクの低い状況：

  • 放牧
  • 厩舎での飼育
  • ウォーキング、乗馬、低強度の運動
  • 保温が有益となる冬の環境

暖かさ自体が必ずしも敵ではありません。問題となるのは、激しい動きの最中やその後に過剰に発生し、閉じ込められた熱です。

まとめ：

馬の脚が温かいことが、直ちに危険を意味するわけではありません。腱は温まるようにできており、温まることでより弾力性が増し、エネルギーを吸収・放出する能力が向上します。問題が生じるのは、熱が過剰になり閉じ込められた場合だけで、特にブーツが自然な冷却を妨げる可能性がある激しい運動中やその後に起こります。
穏やかな気温や寒い環境の厩舎や放牧では、馬の腱ははるかに少ない熱を発生させるため、オーバーヒートの可能性は低く、むしろ寒い天候では暖かさが快適さと可動性をサポートすることもあります。皮膚の健康も重要な要素です。ブーツの下に湿気が閉じ込められると、注意していなければ皮膚炎を引き起こす可能性があります。
通気性の良い素材を選び、毎日脚の状態を確認し、熱が問題となる状況を理解することで、一年を通じて保護、快適さ、健康な四肢の機能を両立できます。

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