(저중량 고반복? 고중량 저반복?)-지근, 속근 편

안녕하세요😃

여러분들은 지근과 속근에 대해 들어보셨나요? 운동에서 끝나지 않고 근육에 대한 이론적인 면도 관심을 가지는 분이라면 한번쯤 들어봤을 내용이죠.

오늘은 바로 이 지근과 속근에 대해 알아보려 합니다.

 

먼저 근섬유에는 크게 지근섬유와 속근섬유로 볼 수 있습니다. 근섬유 자체는 개수와 특성이 결정되어 태어나기 때문에 어떠한 근육에 특정한 근섬유만으로 구성되는 것은 아닙니다.

각 근육 특성에 따라 지근과 속근 섬유들이 적절하게 엉켜 있죠.

아래의 표로 간략히 각각의 특징을 보여드리겠습니다.

 

 

표에서 보시다시피 지근과 속근의 가장 큰 차이는 '무엇을 연료로 쓰느냐'와 '수축 속도'라고 할 수 있습니다. 지근을 적색근이라 부르고 속근을 백색근이라 부르는 이유도 표에 나와있는 미오글로빈의 차이 때문입니다. 

미오글로빈은 산소를 옮기는 붉은 색 색소인데, 이 미오글로빈이 많이 함유 된 지근은 유산소 성 대사가 원활하다는 의미입니다. 하지만 얻는게 있으면 잃는게 있죠. 

지근은 유산소 대사가 원활 하지만 그에 비해 무산소 에너지원인 ATP나 크레아틴을 쓰는 능력이 현저하게 떨어집니다. 

즉, 오래 사용할 수 있지만 힘이 약하다는 거죠. 그렇기 때문에 우리 신체의 버티는 부분을 주로 맡습니다. 종아리의 가자미근, 혹은 복근, 전완근 등에 많이 존재하며 운동을 해도 부피가 잘 커지지 않습니다.

 

반면 속근의 경우 유산소 대사 능력이 거의 없지만 ATP와 크레아틴의 무산소성 에너지 대사에 장점을 가지고 있기에 수축이 빠르고 강력합니다. 지근과 반대격인 만큼 지구력은 약하지만 말이죠.

그래서 속근은 힘과 순발력 등이 필요한 삼두근, 흉근, 햄스트링 등에 많이 분포 되어 있습니다.

여기서 지근과 조금 다른 점은 속근의 경우 두 가지의 유형을 가지고 있는데 하나는 위에서 설명 드린 속근의 본래의 특성을 지닌 2b형, 속근의 특성을 가지면서 산소를 이용해 글리코겐까지 태울 수 있는 2a형이 있습니다. (최근 몇몇 조사에 따르면 훈련을 통해 2b형이 2a형으로 바뀌는 것이 발견 됐다고 합니다. 좀 더 다양한 에너지를 쓸 수 있는 근육으로 변한다면 저희에게는 이득이겠죠?)

 

그렇다면 우리의 신체는 지근과 속근 중 어떤 근육을 먼저 사용하게 될까요?

시간의 흐름에 따라 보자면 애석하게도 속근보다 지근을 먼저 사용하게 되는데 이유는 간단합니다. 저희 몸은 최소한의 에너지만 쓰도록 설계 되어 있기 때문이죠.

그래서 일상 생활에 필요한 가벼운 동작들을 수행 할 때 에너지 효율이 높은 지근섬유가 먼저 사용 되고 강한 힘이 필요 없으니 속근섬유는 동원 되지 않게 되는거죠.

 

그럼 속근은 언제 사용 될까요?

아까도 말씀 드렸다시피 순간적으로 강한 힘을 요하거나 지근이 지쳐 있으면 비로소 움직이기 시작합니다.

달리기를 예로 들어 보겠습니다. 일반적인 걷기에는 주로 지근이 사용되고 회복 달리기처럼 가벼운 러닝에는 지근과 2a형이, 전력 달리기에는 지근과 2a,2b 세 가지 모두 쓰이게 되는 거죠.

한마디로 지근은 어느 상황에나 개입이 된다는 말입니다.

속근을 어서 끌어내 고강도 훈련을 하고 싶은 저희에게는 안타까운 신체 원리이지만, 이런 싸이클이 존재하지 않는다면 아마 엄청난 피로감에 휩싸이겠죠?

생각해보세요. 걷는 한걸음 한걸음이 스쿼트 한번과 같다고 말이죠.

 

우리는 그럼 어떻게 운동을 실시 해야 원하는 목표에 도달 할 수 있을까요?

고중량 저반복? 저중량 고반복? 매체들이 발전 함에 있어 너무 많은 정보들이 유입되고 있습니다. 그에 따른 이점이 상당하지만 저와 같은 팔랑 귀들은 무엇을 선택해야 할 지 혼란스럽기도 하죠.

하지만 한가지 확실 한 건 시작하는 단계에서는 무조건 중량을 낮게 설정하고 자세부터 익히는 것이 정답입니다. 대게 친구들에게 운동을 배우게 되면 처음부터 본인의 무게와 비슷하게 설정하여 가르쳐 주거나 하는데 상당히 위험한 부상을 야기 할 수 있습니다.

일정 기간 자세를 연습했다면 제가 추천 드리는 방법은 아래와 같습니다.

 

1.     파워 리프팅과 같이 무게를 늘리고 싶은 분

요즘 유명한 5x5 루틴이 있죠. 일반적으로 고중량이라고 하면 4~5회 들 수 있는 무게입니다.

여기서 4~5회 들 수 있다는 것은 정말 저 개수만 들고 근육이 완전 지쳐버리는 무게를 말합니다. 이런 형식의 운동은 대게 근원섬유를 발달시켜 근력을 증진시킴에 유용합니다.

 

2.     근육의 부피를 늘리고 싶은 분

요즘에 파워 리프팅이라는 분야가 각광 받고 있지만 아직은 몸의 전체적인 모습과 부피를 중요시 여기는 분들이 많은 것 같습니다.

근육의 부피를 키우고 싶다면 6~12회 정도 반복으로 근육이 지쳐버리는 중량을 설정하시고 수행하면 됩니다. 이런 경우 근원섬유가 발달하는 1번과 다르게 근육세포질망 등 보조 조직을 더 발달시켜 부피를 키우기에 용이합니다.

 

3.     기능적인 면을 중요시 하는 분

사실 2번에 비해 더 높은 반복 횟수는 유산소 운동에 수렴해 근지구력의 영역이죠.

지근을 보조하기 위해 속근이 계속적으로 개입하기 때문에 고른 발달을 기대 할 수 있겠습니다. 이런 분들은 미용적인 면보다 협응력과 기능성이 강조되는 운동이 맞다고 볼 수 있겠네요.

 

위에서 알려드린 방법들이 절대적이라고 하진 않겠습니다. 몸에서 흑백 논리는 적용 되지 않는다고 생각하기 때문이죠. 세 가지 방법은 별개의 개념이 아니라 서로 보완되는 개념이라 생각 하면 되겠습니다.

 

오늘 포스팅은 여기서 마치도록 하겠습니다.

다음에 더 좋은 글과 정보로 찾아 뵙겠습니다. 감사합니다.🙇🏻

 

 

 

Hello everyone! 😃

Have you ever heard of slow-twitch and fast-twitch muscle fibers? If you’re someone who enjoys not only exercising but also learning about the theory behind muscles, you’ve probably come across these terms before. Today, we’re going to dive deep into the differences between slow-twitch and fast-twitch muscle fibers.

Muscle fibers can be generally categorized into two types: slow-twitch and fast-twitch. Each person is born with a certain number and proportion of these fibers, and no muscle consists of just one type. Instead, they are mixed together depending on the muscle’s function. Here’s a quick table to show the key characteristics of each:

(Here you would include the table for reference)

As you can see, the main differences between slow-twitch and fast-twitch fibers lie in their fuel sources and contraction speed. Slow-twitch fibers, often referred to as "red fibers," are rich in myoglobin, a red pigment that helps transport oxygen, which is why these fibers are efficient in aerobic metabolism. However, this comes with a trade-off. While slow-twitch fibers are great for endurance, they are not as powerful when it comes to anaerobic energy sources like ATP and creatine. In other words, they can sustain activity for a long time but aren’t very strong. That’s why you’ll find more slow-twitch fibers in muscles that are responsible for endurance, such as the soleus in your calves, your abdominal muscles, and your forearms. These muscles don’t bulk up easily, even with consistent training.

On the other hand, fast-twitch fibers are poor at aerobic metabolism but excel in anaerobic energy systems, like using ATP and creatine. This makes them fast and powerful, but less enduring. Fast-twitch fibers are dominant in muscles like your triceps, chest, and hamstrings, where explosive strength and speed are key. There are also two types of fast-twitch fibers: type 2b, which is purely anaerobic, and type 2a, which can use oxygen to burn glycogen, giving it more endurance than pure type 2b fibers. Interestingly, some studies suggest that with training, type 2b fibers can convert to type 2a, which would give us a performance advantage by allowing our muscles to use a broader range of energy sources.

Now, which muscle fibers does our body use first? Unfortunately for those of us eager to tap into that explosive power, slow-twitch fibers are activated first. This is because our body is designed to use energy efficiently, and slow-twitch fibers are perfect for low-energy, everyday movements. Only when more force is required or when the slow-twitch fibers become fatigued do the fast-twitch fibers kick in.

For example, if you're walking, your body mostly uses slow-twitch fibers. In a light jog, both slow-twitch and type 2a fibers are engaged, and during an all-out sprint, all three types – slow-twitch, type 2a, and type 2b – are activated. In short, slow-twitch fibers are involved in nearly all types of movement. Although we might want to jump right into high-intensity training, this balance prevents us from getting overwhelmed by fatigue. Imagine if every step you took was as exhausting as a squat – it wouldn’t be sustainable!

So, how should we train to achieve our fitness goals? Should you go for high weight, low reps, or low weight, high reps? With so much information available, it can be hard to choose the right approach. But one thing is certain: if you’re a beginner, always start with lighter weights and focus on mastering your form. Many people make the mistake of lifting too heavy too soon, which can lead to serious injuries.

Once you've built a solid foundation of proper technique, here’s what I recommend based on your goals:

1. For those looking to increase strength (Powerlifting style): If you want to lift heavier weights, there’s a popular routine called the 5x5. High weight typically refers to a weight you can lift 4-5 times before reaching complete fatigue. This style of training primarily focuses on developing your muscle fibers, increasing raw strength.
2. For those aiming to build muscle size: If hypertrophy, or increasing muscle volume, is your goal, aim for 6-12 reps with a weight that leaves you exhausted by the end. Unlike strength training, which develops the muscle fibers themselves, this type of training promotes the growth of surrounding tissue, making it effective for increasing muscle size.
3. For those focusing on functional fitness: Higher repetition ranges beyond 12 are usually more about endurance, as they engage both slow-twitch and fast-twitch fibers continuously. This leads to well-rounded development and is ideal for people who prioritize coordination and functional movement over aesthetics.

Now, these aren’t hard and fast rules. Our bodies aren’t governed by black-and-white principles. Instead, think of these methods as complementary strategies rather than completely separate concepts.

That wraps up today’s video! I hope this information helps you make better decisions in your training. I’ll be back with more tips and insights, so stay tuned. Thanks for watching! 🙇🏻