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A2 noun #4,500 most common 10 min read

筋肉

kinniku Top 4,500

Practice it Examples Notes & Tips 筋肉 in 30 Seconds

Explanation 筋肉 in your Level:

At the A1 level, you should learn 'kinniku' as a basic body part word, similar to 'te' (hand) or 'ashi' (leg). You don't need to know complex medical terms, but you should be able to say things like 'I have muscles' or 'My muscles hurt' in simple sentences. At this stage, focus on the katakana word 'jimu' (gym) and how 'kinniku' relates to it. You will likely see this word in basic health chapters of textbooks. The main goal is to recognize the kanji and associate it with the English word 'muscle.' You might use it to describe a hero in a cartoon or a strong person you know using basic 'desu' and 'masu' forms. Simple particles like 'ga' and 'no' are your best friends here. For example, 'Watashi no kinniku' (My muscle) or 'Kinniku ga sugoi' (Muscles are amazing).

At the A2 level, you begin to use 'kinniku' with more dynamic verbs. You should learn the phrase 'kinniku ga tsuku' (to gain muscle) and 'kinniku wo kitaeru' (to train muscles). You can describe your hobbies, such as going to the gym or playing sports, and explain the physical results. You should also be able to use 'kinnikutsū' (muscle pain) to explain why you are tired or why you can't do something. At this level, you start to understand the difference between 'kinniku' (the muscle itself) and 'chikara' (strength). You can use 'node' or 'kara' to give reasons: 'Kinō undō shita node, kinniku ga itai desu' (Because I exercised yesterday, my muscles hurt). You are moving from just labeling the body to describing its state and the actions you take to change it.

At the B1 level, you can use 'kinniku' in more complex social and health contexts. You should be familiar with common compounds like 'kinnikushitsu' (muscular build) and 'kinnikuryō' (muscle mass). You can follow a simple Japanese workout video or read a basic health article. You understand the nuance of verbs like 'hogusu' (to loosen) and 'hikishimeru' (to tighten/tone). You can discuss your fitness goals in more detail, using grammar like '～te miru' (try doing) or '～tari ～tari' (doing things like...). For example, 'Kinniku wo tsukeru tame ni, tanpaku-shitsu wo takusan toru yō ni shite imasu' (In order to gain muscle, I am trying to take a lot of protein). Your vocabulary expands to include specific muscle groups like 'fukkin' (abs) or 'haikin' (back muscles) because they appear so often in daily life.

At the B2 level, you can use 'kinniku' in professional or semi-formal settings. You can explain the physiological benefits of exercise or discuss the anatomy of an injury with a doctor. You understand metaphorical uses and can identify 'kinniku' in literary or idiomatic contexts, even if they are rare. You can read news articles about health trends or sports science that use terms like 'kinniku genshō' (muscle loss) or 'kinniku zōkyō-zai' (performance-enhancing drugs). You are comfortable with various registers, knowing when to use 'kinniku' versus more technical terms like 'kin-soshiki' (muscle tissue). You can debate the merits of different training styles and use advanced grammar like '～ni tomonatte' (along with) to describe how muscles change with age or activity levels.

At the C1 level, your understanding of 'kinniku' includes its role in Japanese culture, media, and advanced science. You can appreciate the humor in 'kinniku' memes and understand the nuances of how 'kinniku' is used in different genres of literature. You can discuss the biochemical process of muscle hypertrophy (kinniku hidai) or the mechanics of muscle contraction (kinniku shūshuku) in detail. You can navigate complex medical documents and understand the societal implications of physical fitness in Japan. Your usage is indistinguishable from a native speaker, including the correct use of subtle onomatopoeia like 'morimori,' 'mukimuki,' or 'pittari' to describe different types of muscularity. You can also use 'kinniku' in abstract arguments about physical versus mental discipline.

At the C2 level, you have a complete mastery of 'kinniku' and its place in the Japanese linguistic landscape. You can understand and use highly specialized anatomical terms that use the 'kin' (筋) root. You can analyze the etymological history of the word and how its usage has evolved from classical Japanese to the modern era. You can engage in high-level academic discussions regarding kinesiology, sports medicine, or physical education policy. You understand the subtle socio-linguistic markers associated with 'muscle talk' in different subcultures. You can translate complex English texts about physiology into natural Japanese, choosing the perfect synonyms for 'muscle' depending on the specific scientific or poetic context. You are also aware of rare archaic terms for muscle and how they differ from modern 'kinniku.'

Practice it Examples Notes & Tips

筋肉 in 30 Seconds

筋肉 (kinniku) is the standard Japanese word for 'muscle,' used in both casual and medical contexts.
Commonly paired with verbs like 'tsuku' (to gain) and 'kitaeru' (to train/forge).
The word for muscle pain or soreness is 'kinnikutsū,' a very frequent daily term.
It is a compound of 'suji' (fiber/tendon) and 'niku' (meat), literally meaning 'fibrous meat.'

The Japanese word 筋肉 (kinniku) is the primary term for 'muscle.' It is a compound noun formed by two kanji: 筋 (suji), which refers to a fiber, line, or tendon, and 肉 (niku), which means meat or flesh. Together, they literally describe 'fibrous meat,' which is a perfect anatomical description of muscle tissue. In modern Japanese, this word is used in almost every context where English speakers would use 'muscle,' from biological discussions to fitness goals and even metaphorical expressions of strength.

Anatomical Context: In a medical or biological sense, 筋肉 refers to the various types of muscle tissue in the human body, such as skeletal muscle, smooth muscle, and cardiac muscle. Doctors and physical therapists use this term when discussing injuries or physical development.
Fitness and Bodybuilding: This is perhaps the most common daily usage. When someone talks about 'gaining muscle' or 'working out,' 筋肉 is the central word. It is associated with the gym culture (kinniku-tore) and the aesthetic of a well-built body.

毎日のトレーニングで、素晴らしい筋肉がつきましたね。(Mainichi no torēningu de, subarashii kinniku ga tsukimashita ne.)

Translation: Through daily training, you've gained wonderful muscles, haven't you?

Culturally, Japan has a fascination with 'kinniku' that manifests in various ways, from the popular 'Kinnikuman' manga series to the 'Muscle Musical' and the ubiquitous 'Kinniku-tore' (muscle training) boom. Unlike some words that might have different nuances in English, 筋肉 remains quite stable as a direct equivalent. However, it is important to note that while 'muscle' in English can sometimes mean 'influence' (e.g., 'political muscle'), in Japanese, 筋肉 is almost exclusively physical. For influence, one would use words like 影響力 (eikyōryoku) or 権力 (kenryoku).

彼は筋肉痛で動けません。(Kare wa kinnikutsū de ugokemasen.)

Translation: He cannot move due to muscle pain (soreness).

Register and Nuance: The word is neutral and can be used in formal medical reports, casual gym talk, or children's education. It is neither particularly polite nor rude, though discussing someone's muscles too intensely might be seen as overly familiar or 'macho' depending on the social setting.

プロのスポーツ選手は筋肉の柔軟性が重要です。(Puro no supōtsu senshu wa kinniku no jūnansei ga jūyō desu.)

Translation: For professional athletes, muscle flexibility is important.

この魚の筋肉は引き締まっています。(Kono sakana no kinniku wa hikishimatte imasu.)

Translation: The muscle of this fish is firm.

Compound Words: Common compounds include 筋肉質 (kinnikushitsu - muscular build), 筋肉増強 (kinniku zōkyō - muscle enhancement), and 筋肉バカ (kinniku baka - a 'muscle head' or someone obsessed with working out).

彼は筋肉を鍛えるのが趣味です。(Kare wa kinniku wo kitaeru no ga shumi desu.)

Translation: His hobby is training his muscles.

Using 筋肉 in a sentence requires understanding the specific verbs that typically pair with it. Unlike English where we 'get' muscles, in Japanese, muscles 'attach' to you or you 'forge' them. The grammar is straightforward, but the collocations (natural word pairings) are what make you sound like a native speaker. Let's break down the most common patterns and sentence structures used for beginners through intermediate learners.

Pattern 1: Gaining Muscle: The most common way to say 'to gain muscle' is 筋肉がつく (kinniku ga tsuku). Here, the particle 'ga' indicates the subject (muscle), and 'tsuku' means to attach or be acquired. If you want to say you are actively trying to gain muscle, you might use 筋肉をつける (kinniku wo tsukeru).

ジムに通って、足に筋肉がつきました。(Jimu ni kayotte, ashi ni kinniku ga tsukimashita.)

Translation: By going to the gym, I gained muscle in my legs.

Pattern 2: Training Muscle: To say 'to train' or 'to work out' muscles, the verb 鍛える (kitaeru) is used. This verb has a nuance of forging something like steel, making it stronger and more resilient. It is the standard term for physical training.

背中の筋肉を鍛えるのは難しいです。(Senaka no kinniku wo kitaeru no wa muzukashii desu.)

Translation: Training back muscles is difficult.

Another vital phrase is 筋肉痛 (kinnikutsū), which translates to muscle pain or soreness. This is used specifically for the soreness felt after exercise (DOMS). It is used with the verb 'naru' (to become) or 'ga aru' (to have). For example, 'Kinnikutsū ni narimashita' (I got muscle soreness).

昨日走りすぎたので、今日は筋肉痛がひどいです。(Kinō hashirisugita node, kyō wa kinnikutsū ga hidoi desu.)

Translation: Because I ran too much yesterday, the muscle soreness is terrible today.

Pattern 3: Describing Qualities: You can use adjectives like 柔らかい (yawarakai - soft/flexible) or 硬い (katai - hard/stiff) to describe the state of muscles. In sports science, 'soft' muscles are often seen as better for explosive power.

ストレッチをして、筋肉をほぐしてください。(Sutoretchi wo shite, kinniku wo hogushite kudasai.)

Translation: Please stretch and loosen your muscles.

加齢とともに、筋肉量は減少します。(Karei to tomo ni, kinnikuryō wa genshō shimasu.)

Translation: As you age, muscle mass decreases.

Metaphorical Use: While rare, you might hear 筋肉 used in a joking way to describe someone's thought process as being 'all muscle' (all brawn, no brains), often phrased as 'Kinniku de kangaete iru' (thinking with muscles).

腹筋の筋肉が割れています。(Fukkin no kinniku ga warete imasu.)

Translation: His abdominal muscles are ripped (split).

If you spend any time in Japan, you will encounter the word 筋肉 in a variety of settings. It is a 'high-frequency' word because of Japan's health-conscious culture and the popularity of sports. Here are the most likely places you will hear or see it used naturally.

The Fitness Center (Gym): In a gym (スポーツジム), trainers will constantly use this word. You'll hear phrases like 'Kinniku ni kikaeru' (literally 'to make it work on the muscle' or 'to target the muscle'). Posters will advertise 筋肉増強 (muscle building) supplements or protein powders.

もっと筋肉を意識して動かしましょう。(Motto kinniku wo ishiki shite ugokashimashō.)

Translation: Let's move while being more conscious of the muscle.

Anime and Manga: Shonen anime is famous for its focus on physical training. Characters often shout about their training regimes. Series like 'Dumbbell Nan-Kilo Moteru?' (How Heavy Are the Dumbbells You Lift?) are entirely centered around 筋肉 and explain muscle groups in detail. You'll hear terms like 大胸筋 (daikyōkin - pectoralis major) frequently.

修行のおかげで、鋼のような筋肉を手に入れた。(Shugyō no okage de, hagane no yō na kinniku wo te ni ireta.)

Translation: Thanks to my training, I've obtained muscles like steel.

Medical and Health Checkups: During the annual health check (kenkō shindan) in Japan, doctors may discuss your muscle mass (kinnikuryō) as an indicator of health, especially for the elderly to prevent sarcopenia (kinniku genshō-shō).

この注射は筋肉内注射です。(Kono chūsha wa kinnikunai chūsha desu.)

Translation: This injection is an intramuscular injection.

Television variety shows often feature physical challenges (like 'Sasuke,' known as 'Ninja Warrior' abroad). Commentators will marvel at the contestants' 筋肉. You'll hear adjectives like 'sugoi' (amazing) or 'utsukushii' (beautiful) used to describe them. Even in the supermarket, you might see labels on meat that describe the 'suji' (muscle/tendon) content, though 筋肉 is usually reserved for living tissue or specifically functional muscle.

彼は筋肉の動きを研究しています。(Kare wa kinniku no ugoki wo kenkyū shite imasu.)

Translation: He is studying the movement of muscles.

Daily Conversation: Friends might tease each other about being 'kinniku baka' (muscle-obsessed) or complain about 'kinnikutsū' after a weekend hike. It's a very grounded, everyday word.

階段を上るだけで筋肉が疲れます。(Kaidan wo noboru dake de kinniku ga tsukaremasu.)

Translation: My muscles get tired just from climbing the stairs.

最新のロボットは筋肉のような動きをします。(Saishin no robotto wa kinniku no yō na ugoki wo shimasu.)

Translation: The latest robots move like muscles.

While 筋肉 is a direct translation of 'muscle,' English speakers often make mistakes regarding its usage in idiomatic expressions or confusing it with related Japanese words. Understanding these pitfalls will help you communicate more accurately.

Mistake 1: Using 筋肉 for 'Strength': In English, we might say 'He has a lot of muscle' to mean 'He is very strong.' In Japanese, you must distinguish between the tissue (筋肉) and the power (力 - chikara). If you say 'Kinniku ga arimasu,' you are specifically commenting on the physical mass. If you want to say someone is strong, use 'Chikara ga tsuyoi.'

❌ 彼は筋肉が強いです。(Kare wa kinniku ga tsuyoi desu.) - Sounds unnatural.
✅ 彼は力があります。(Kare wa chikara ga arimasu.) - He is strong/powerful.

Mistake 2: Confusing 筋肉 with 筋 (Suji): While 'suji' is the first kanji in kinniku, as a standalone word, it often refers to 'tendons,' 'sinew,' or the 'stringy parts' of meat and vegetables. In a culinary context, if you say the meat has 'kinniku,' it's weird. You should say it has 'suji' (gristle/tendon).

❌ この肉は筋肉が多い。(Kono niku wa kinniku ga ooi.) - This meat has many muscles (weird).
✅ この肉は筋が多い。(Kono niku wa suji ga ooi.) - This meat is stringy/gristly.

Mistake 3: Literal translation of 'Muscle through': English uses 'muscle' as a verb (to muscle through something). Japanese does not. You cannot use 筋肉 as a verb. Instead, use 'gouin ni' (forcibly) or 'chikara-waza' (a power move).

❌ 彼はその仕事を筋肉した。(Kare wa sono shigoto wo kinniku shita.) - Nonsense.
✅ 彼は力技でその仕事を終わらせた。(Kare wa chikarawaza de sono shigoto wo owaraseta.) - He finished the job through sheer force.

Mistake 4: Particle Errors: Learners often use the wrong particle with 'tsuku' (to gain). It should be 'ga tsuku' because the muscle is the thing appearing. Using 'wo tsuku' is a common error.

❌ 筋肉を付きたい。(Kinniku wo tsukitai.) - Incorrect particle.
✅ 筋肉をつけたい。(Kinniku wo tsuketai.) - I want to put on muscle (active).
✅ 筋肉がつきたい。(Kinniku ga tsukitai.) - (Less common but grammatically okay) I want muscle to attach.

腹筋を筋肉と呼びますが、腹肉とは言いません。(Fukkin wo kinniku to yobimasu ga, fukuniku to wa iimasen.)

Translation: We call abs 'kinniku,' but we don't say 'fukuniku' for belly fat (we say 'zeiniku').

While 筋肉 is the general term, Japanese has several specific words depending on whether you are talking about anatomy, strength, or physical build. Knowing these will help you choose the most appropriate word for the situation.

筋 (Suji) - Tendon/Fiber: As mentioned before, 'suji' focuses on the fibrous nature. Use this when talking about a pulled tendon (suji wo chigaeru) or stringy meat. It's more about the 'lines' of the body than the 'mass.'
力 (Chikara) - Strength/Power: This is the abstract concept of power. You can have 'chikara' without having visible 'kinniku' (like a small but strong person). 筋肉 is the physical engine; 力 is the output.
体格 (Taikaku) - Physique/Build: If you want to describe someone's overall body shape, 'taikaku' is better. 'Kare wa taikaku ga ii' means he has a good build, which might include being muscular, tall, and broad-shouldered.

彼は筋肉質というよりは、がっしりした体格だ。(Kare wa kinnikushitsu to iu yori wa, gasshiri shita taikaku da.)

Translation: Rather than being muscular, he has a sturdy build.

身 (Mi) - Flesh/Body: Usually used for the meat of fish or fruit, or in phrases like 'mi wo hikishimeru' (to brace oneself). It refers to the substance of the body but lacks the functional 'muscle' nuance of 筋肉.

筋力 (Kinryoku) - Muscle Strength

Wait, there is also 筋力 (kinryoku). This is a very common alternative. While 筋肉 is the 'muscle' itself, 筋力 is 'muscle power.' In sports and physical therapy, you'll hear 'kinryoku' more often when discussing performance. For example, 'kinryoku torēningu' (strength training) is synonymous with 'kinniku-tore.'

腹筋 (Fukkin) - Abdominal muscles. This is a specific type of 筋肉. Note how 'kinniku' is often shortened to just 'kin' in compounds.

背筋 (Haikin) - Back muscles: Used similarly to fukkin. You'll hear 'haikin wo kitaeru' (train the back muscles).

彼は筋肉モリモリだ。(Kare wa kinniku morimori da.)

Translation: He is super buff (onomatopoeic 'morimori' for bulging muscles).

How Formal Is It?

Fun Fact

The character 筋 contains the radical for bamboo (竹) because tendons were thought to look like bamboo fibers or be as resilient as bamboo.

Pronunciation Guide

UK kʲiɲːikɯ

US kʲinːiku

The pitch accent is 'Heiban' (Flat). Kinniku [0]. This means the pitch starts low and stays high for the rest of the word.

Rhymes With

Shin'niku (New meat) Shinniku (Flesh and blood) Ten'niku (Heavenly meat - rare) Kan'niku (Canned meat) Gunniku (Army meat - rare) Hinniku (Irony - though different kanji) Zenniku (Whole meat) Rinniku (Phosphorous meat - rare)

Common Errors

Pronouncing 'niku' as 'neeku' (like knee).
Stressing the first syllable like English 'MUS-cle'.
Failing to double the 'n' sound (it's kin-niku, not kiniku).
Making the final 'u' too long.
Incorrect pitch accent (rising on 'ni').

Difficulty Rating

Reading 2/5

Kanji are common but 筋 has many strokes.

Writing 3/5

Writing 筋 correctly requires attention to the bamboo radical.

Speaking 1/5

Pronunciation is very simple and flat.

Listening 1/5

Distinct sound, easy to pick out in conversation.

What to Learn Next

Prerequisites

体肉力痛い強い

Learn Next

鍛える柔軟運動健康骨

Advanced

収縮肥大萎縮骨格筋腱

Grammar to Know

Noun + がつく

筋肉がつく (To gain muscle)

Noun + を鍛える

筋肉を鍛える (To train muscle)

Noun + になる

筋肉痛になる (To get muscle soreness)

Adjective + 筋肉

強い筋肉 (Strong muscle)

Noun + の + 筋肉

足の筋肉 (Leg muscle)

Examples by Level

私の筋肉は大きいです。

My muscles are big.

Simple A wa B desu structure.

筋肉が痛いです。

My muscles hurt.

Subject + ga + adjective.

彼はすごい筋肉を持っています。

He has amazing muscles.

Using 'motte iru' for possession.

これは筋肉の絵です。

This is a picture of a muscle.

Possessive 'no'.

筋肉を動かします。

I move my muscles.

Object + wo + verb.

強い筋肉がほしいです。

I want strong muscles.

Desire form 'hoshii'.

筋肉は赤いです。

Muscles are red.

Topic marker 'wa'.

毎日、筋肉を見ます。

I look at my muscles every day.

Adverb 'mainichi'.

ジムで筋肉を鍛えています。

I am training my muscles at the gym.

Continuous form 'te-iru'.

走ったので、筋肉痛になりました。

Because I ran, I got muscle soreness.

Reason 'node' + change 'ni naru'.

もっと筋肉をつけたいです。

I want to put on more muscle.

Volitional 'tai'.

彼の筋肉はとても硬いです。

His muscles are very hard.

Adverb 'totemo' + adjective.

お風呂で筋肉をほぐします。

I loosen my muscles in the bath.

Locative 'de'.

筋肉がつくと嬉しいです。

I'm happy when I gain muscle.

Conditional 'to'.

足の筋肉が弱いです。

My leg muscles are weak.

Specific part 'no' kinniku.

筋肉のためにプロテインを飲みます。

I drink protein for my muscles.

Purpose 'no tame ni'.

筋肉を鍛えることで、代謝が上がります。

By training muscles, your metabolism increases.

Means 'koto de'.

彼は筋肉質な体型をしています。

He has a muscular build.

Compound 'kinnikushitsu'.

筋肉を傷めないように、ストレッチをしましょう。

Let's stretch so as not to hurt our muscles.

Purpose 'yō ni'.

加齢によって筋肉量は減少します。

Muscle mass decreases due to aging.

Cause 'ni yotte'.

腹筋だけでなく、背筋も鍛えるべきです。

You should train not only your abs but also your back muscles.

Not only 'dake de naku'.

筋肉の疲れがなかなか取れません。

The muscle fatigue just won't go away.

Negative potential 'toremasen'.

効率よく筋肉を増やす方法を教えてください。

Please tell me how to increase muscle efficiently.

Adverbial 'efficiently'.

彼の筋肉は隆々としていて、驚きました。

I was surprised because his muscles were bulging.

Onomatopoeia 'ryūryū'.

筋肉の柔軟性を保つことは、怪我の予防に繋がります。

Maintaining muscle flexibility leads to injury prevention.

Nominalizer 'koto' + result 'ni tsunagaru'.

無理なトレーニングは筋肉を破壊する恐れがあります。

Excessive training risks damaging (destroying) muscles.

Fear/risk 'osore ga aru'.

プロの選手は、筋肉の微細な変化に敏感です。

Professional athletes are sensitive to subtle changes in their muscles.

Target 'ni' + adjective 'binkan'.

このサプリメントは筋肉の回復を早めます。

This supplement speeds up muscle recovery.

Causative-like 'hayamemasu'.

筋肉が収縮することで、関節が動きます。

Joints move by muscles contracting.

Technical term 'shūshuku'.

彼は筋肉の構造について論文を書いています。

He is writing a thesis on muscle structure.

Topic 'ni tsuite'.

筋肉を酷使した後は、十分な休息が必要です。

After overusing your muscles, sufficient rest is necessary.

Overuse 'kokushi'.

心臓も一つの大きな筋肉と言えます。

The heart can also be called a large muscle.

Can be said 'to iemasu'.

筋肉肥大を促進するためには、適切な栄養摂取が不可欠だ。

Proper nutrient intake is essential to promote muscle hypertrophy.

Hypertrophy 'hidai' + essential 'fukakesu'.

その選手は、筋肉の連動性を高める練習に注力している。

That athlete is focusing on practice to improve muscle coordination.

Coordination 'rendōsei'.

筋肉の萎縮を防ぐためのリハビリが始まった。

Rehabilitation to prevent muscle atrophy has begun.

Atrophy 'ishuku'.

彼は筋肉の動きをミリ単位で制御できる。

He can control his muscle movements by the millimeter.

Unit 'tan'i'.

この理論は筋肉の疲労メカニズムを解明するものだ。

This theory clarifies the mechanism of muscle fatigue.

Clarify 'kaimei'.

精神的な緊張が筋肉のこわばりを引き起こす。

Mental tension causes muscle stiffness.

Stiffness 'kowabari'.

筋肉の質を評価する新しい指標が導入された。

A new index for evaluating muscle quality was introduced.

Index 'shihyō'.

彼は筋肉の限界に挑む過酷なレースに参加した。

He participated in a grueling race that challenged the limits of his muscles.

Challenge 'idomu'.

筋肉の随意収縮と不随意収縮の差異を論じる。

Discussing the difference between voluntary and involuntary muscle contraction.

Voluntary 'zuii' vs Involuntary 'fuzuii'.

筋線維の組成は遺伝的要因に大きく左右される。

The composition of muscle fibers is greatly influenced by genetic factors.

Influenced 'sayū sareru'.

その彫刻は、人間の筋肉美を極限まで表現している。

That sculpture expresses the beauty of human musculature to the limit.

Muscular beauty 'kinnikubi'.

加齢に伴う骨格筋の機能低下は、QOLに直結する課題である。

The decline in skeletal muscle function associated with aging is an issue directly linked to QOL.

Directly linked 'chokketsu'.

筋肉の緊張を緩和するための薬理学的なアプローチが検討されている。

Pharmacological approaches to alleviate muscle tension are being considered.

Pharmacological 'yakurigakuteki'.

彼は筋肉の解剖学的な知識を駆使して、独自のトレーニング法を編み出した。

By making full use of anatomical knowledge of muscles, he devised a unique training method.

Full use 'kushi' + devise 'amidashita'.

筋肉の深層部における炎症が、慢性的な痛みの原因となっていた。

Inflammation in the deep layers of the muscle was the cause of chronic pain.

Deep layer 'shinsōbu'.

最新の義手は、残存する筋肉の電気信号を感知して動作する。

Modern prosthetic hands operate by sensing electrical signals from remaining muscles.

Remaining 'zanzon' + sense 'kanchi'.

Common Collocations

筋肉がつく

筋肉を鍛える

筋肉痛になる

筋肉をほぐす

筋肉をいじめる

筋肉が落ちる

筋肉を伸ばす

筋肉が震える

筋肉が割れる

筋肉を休める

Common Phrases

筋肉痛

— Muscle soreness after exercise.

明日は筋肉痛になりそうだ。

筋肉質

— A muscular body type.

彼は筋肉質の体型だ。

筋肉バカ

— Someone who thinks only about working out.

彼は自他共に認める筋肉バカだ。

筋肉隆々

— Having bulging, impressive muscles.

筋肉隆々のボディビルダー。

筋肉トレーニング

— Muscle training (often shortened to 筋トレ).

健康のために筋肉トレーニングをする。

筋肉量

— The amount of muscle mass in the body.

筋肉量を測定する。

筋肉増強

— The act of increasing or building muscle.

筋肉増強剤の使用は禁止だ。

筋肉組織

— Muscle tissue (anatomical term).

筋肉組織の顕微鏡写真。

筋肉疲労

— Muscle fatigue.

筋肉疲労が蓄積している。

筋肉の衰え

— The weakening or atrophy of muscles.

筋肉の衰えを感じる。

Often Confused With

筋肉 vs 力 (Chikara)

Chikara is abstract power; Kinniku is the physical mass.

筋肉 vs 筋 (Suji)

Suji is fibers/tendons/lines; Kinniku is the whole muscle tissue.

筋肉 vs 身 (Mi)

Mi is general flesh/meat; Kinniku is functional muscle.

Idioms & Expressions

"筋肉で考える"

— To act without thinking, relying only on physical force or instinct.

彼は何でも筋肉で解決しようとする。

Informal/Joking

"筋がいい"

— To have a natural talent or aptitude (uses the 'suji' kanji).

君はテニスの筋がいいね。

Neutral

"筋を通す"

— To act according to logic or principles (uses 'suji').

彼は最後まで筋を通した。

Neutral

"腹筋が崩壊する"

— To laugh so hard your stomach muscles 'collapse.'

あの動画は腹筋崩壊ものだ。

Slang/Internet

"筋肉は裏切らない"

— A famous catchphrase: 'Muscles don't betray you' (hard work always shows).

努力すれば筋肉は裏切らない。

Popular Culture

"力技でいく"

— To force something through using sheer power.

交渉を力技でまとめる。

Neutral

"見せ筋"

— Muscles that are just for show and not functional.

あれはただの見せ筋だ。

Informal

"筋肉美"

— The aesthetic beauty of a muscular body.

ギリシャ彫刻の筋肉美。

Neutral

"筋金入り"

— Hardcore, staunch, or dyed-in-the-wool (literally 'with a metal core').

彼は筋金入りのマニアだ。

Neutral

"身を粉にする"

— To work oneself to the bone (literally 'grind one's flesh to powder').

家族のために身を粉にして働く。

Idiomatic

Easily Confused

筋肉 vs 筋肉痛

Learners might just say 'kinniku itai'.

Kinnikutsū is the specific noun for exercise-induced soreness.

Kinnikutsū ga hidoi.

筋肉 vs 筋力

Often used interchangeably with 筋肉.

Kinryoku is the 'power' (output); Kinniku is the 'muscle' (organ).

Kinryoku wo sokutei suru.

筋肉 vs 筋肉質

Used to describe a person.

Kinniku is the noun; Kinnikushitsu is the adjective for 'muscular build'.

Kare wa kinnikushitsu da.

筋肉 vs 腹筋

Shortened form.

Fukkin specifically means abdominal muscles.

Fukkin wo 100-kai suru.

筋肉 vs 贅肉

Both contain 'niku'.

Zeiniku is 'excess meat' (fat); Kinniku is muscle.

Zeiniku wo otoshite kinniku wo tsukeru.

Sentence Patterns

[Body Part] no kinniku ga itai desu.

Ashi no kinniku ga itai desu.

Kinniku wo [Verb-tai] desu.

Kinniku wo kitaetai desu.

Kinniku ga tsuita node [Result].

Kinniku ga tsuita node, omoi mono ga motemasu.

Kinniku no [Noun] wo [Verb].

Kinniku no jūnansei wo takameru.

Kinniku ni [Target] shita [Action].

Kinniku ni tokka shita torēningu wo suru.

Kinniku no [Abstract Concept].

Kinniku no zanzon kinō wo katsuyō suru.

Kinniku ga sugoi desu ne.

Mainichi [Activity] shite, kinniku wo tsukemasu.

Mainichi pūru de oyoide, kinniku wo tsukemasu.

Word Family

Nouns

筋肉 (Muscle)

筋力 (Muscle strength)

筋繊維 (Muscle fiber)

腹筋 (Abs)

背筋 (Back muscles)

Verbs

鍛える (To train)

ほぐす (To loosen)

つける (To attach/gain)

収縮する (To contract)

Adjectives

筋肉質な (Muscular)

硬い (Hard/Stiff)

柔らかい (Soft/Flexible)

逞しい (Robust/Sturdy)

プロテイン

ジム

トレーニング

スポーツ

健康

How to Use It

frequency

Very frequent in daily life, health, and sports.

Common Mistakes

筋肉を強い (Kinniku wo tsuyoi) → 筋肉が強い (Kinniku ga tsuyoi)
Adjectives take 'ga', not 'wo'.
筋肉をする (Kinniku wo suru) → 筋トレをする (Kintore wo suru)
You can't 'do' muscle; you 'do' muscle training.
筋肉がつきたい (Kinniku wo tsukitai) → 筋肉をつけたい (Kinniku wo tsuketai)
Use the transitive 'tsukeru' when you are the one making the effort.
肉が痛い (Niku ga itai) → 筋肉が痛い (Kinniku ga itai)
'Niku' alone sounds like you are talking about food or fat.
筋肉の力 (Kinniku no chikara) → 筋力 (Kinryoku)
While not 'wrong', 'Kinryoku' is the standard compound for muscle strength.

Tips

Particle Choice

Always use 'ga' with 'tsuku' (kinniku ga tsuku) to describe the natural result of training.

Macho Culture

The word 'macho' is used in Japan (matcho), but it often implies a very specific bodybuilder look.

Shortcuts

Learn 'Fukkin' (Abs) and 'Haikin' (Back) early, as they are used more than the full names.

Stroke Order

The kanji 筋 has 12 strokes. Practice the 'bamboo' top carefully to keep it legible.

Medical Use

If you go to a clinic for pain, say 'Kinniku ga itai' rather than just 'Karada ga itai' (My body hurts).

Gym Talk

Trainers often use the word 'ishiki' (consciousness). 'Kinniku wo ishiki shite' means 'focus on the muscle'.

Morning Routine

Stretching (sutoretchi) is often described as 'kinniku wo nobasu' (extending the muscles).

Compliments

Telling someone 'Kinniku sugoi desu ne' is a very common and safe compliment for fitness enthusiasts.

Context

Read manga like 'One Punch Man' to see how 筋肉 is used in exaggerated, heroic contexts.

King Meat

Remember: A KING needs MEAT for his MUSCLES (KIN-NIKU).

Memorize It

Mnemonic

Imagine a 'King' (Kin) eating a giant piece of 'Meat' (Niku) to grow his muscles.

Visual Association

Picture the kanji 筋 as a bamboo (竹) frame for a strong body, and 肉 as the steaks you eat to build it.

Word Web

Body Strength Gym Protein Pain Anatomy Movement Fiber

Challenge

Try to name three body parts where you have 筋肉 and say whether they are 'itai' (sore) or 'tsuyoi' (strong).

Word Origin

The word is a Sino-Japanese compound (Kango). '筋' (suji) originally depicted bamboo and strength/tendon, signifying fibers. '肉' (niku) is a pictograph of a piece of meat with ribs.

Original meaning: Fibrous flesh or the stringy parts of meat.

Japonic (Sino-Japanese vocabulary).

Cultural Context

Be careful when commenting on someone's 筋肉; while usually a compliment, some may find it too focus on physical appearance.

English speakers use 'muscle' for influence; Japanese speakers do not use 'kinniku' this way.

Kinnikuman (Anime/Manga) Muscle Museum (Muse song popular in Japan) Kinniku Exercise (NHK TV Show)

Practice in Real Life

Real-World Contexts

At the Gym

筋肉を鍛える
筋肉に効く
筋肉痛
プロテイン

At the Doctor

筋肉が痛い
筋肉が張る
筋肉離れ
筋肉内注射

Sports Commentary

筋肉美
筋肉の連動
筋力がある
筋肉隆々

Cooking

肉の筋
身が引き締まる
筋肉質な肉
筋を取る

Everyday Life

筋肉がついた
筋肉が落ちた
筋肉バカ
ムキムキ

Conversation Starters

"最近、何か筋肉を鍛える運動をしていますか？ (Are you doing any exercise to train your muscles lately?)"

"筋肉痛になったとき、どうしていますか？ (What do you do when you get muscle soreness?)"

"どんな筋肉の部位を一番鍛えたいですか？ (Which part of your muscles do you want to train the most?)"

"筋肉をつけるために食べているものはありますか？ (Is there anything you eat to gain muscle?)"

"あのスポーツ選手の筋肉、すごいと思いませんか？ (Don't you think that athlete's muscles are amazing?)"

Journal Prompts

今日のトレーニングでどの筋肉を鍛えましたか？ (Which muscles did you train in today's workout?)

理想の筋肉について書いてください。 (Write about your ideal muscles/physique.)

筋肉痛で困った経験はありますか？ (Have you ever had trouble due to muscle soreness?)

筋肉を鍛えることのメリットは何だと思いますか？ (What do you think are the benefits of training muscles?)

日本人の筋肉に対するイメージについてどう思いますか？ (What do you think about the Japanese image of muscles?)

Frequently Asked Questions

10 questions

You usually say 'Ashi ga tsuru' (My leg cramped). While it involves 筋肉, the word itself isn't always used in the common phrase.

Yes, it is used for animal muscles too, especially in biological or athletic contexts (like racehorses).

Kitaeru is a native Japanese verb meaning 'to forge/strengthen'. Torēningu is a loanword. Both are common, but 'kitaeru' sounds more disciplined.

Yes, but the specific term 'Shinkin' (心筋) is more common in medical contexts.

You can say 'Kinniku wo kirei ni waritai' (I want to split my muscles beautifully) or 'Mukimuki ni naritai'.

It is neutral. It's perfectly fine to use in any standard conversation.

It is short for 'Kinniku Torēningu' (Weight training/Strength training).

Because muscles are essentially the 'meat' of the body that provides movement.

In very casual or old-fashioned speech, yes, but 'kinniku' is the modern standard.

Yes, it's 'Kinniku no kioku' or more commonly 'Karada ga oboete iru' (The body remembers).