When you throw a punch into a heavy bag, it absorbs your force, swings slightly, and pushes back just enough to mimic real-life resistance.
But have you ever stopped mid-workout and wondered: What are punching bags filled with?
In this post, we’ll break down the most common punching bag fillings, how each impacts training, and what you should look for when choosing a heavy bag for your home gym.
The Purpose Behind the Filling
Before diving into materials, it’s essential to understand why the filling matters. The contents of a punching bag determine:
- The weight of the bag
- How much it swings on impact
- Resistance and impact feel
- Durability and consistency over time
A well-filled heavy bag creates a stable, realistic, striking experience without being too hard on your joints. Conversely, a poorly filled bag may feel lumpy, lose shape, or cause wrist and knuckle strain.
What are Punching Bags Filled With?
Let’s take a closer look at what’s inside these bags and how each type of filling affects your conditioning experience.
Most Common Punching Bag Fillings
1. Textile Scraps (Shredded Fabric)
This is the most common filling for modern heavy bags—and for good reason. Textile or fabric scraps offer a consistent, dense, and shock-absorbing experience. They mimic the feel of hitting muscle, making them ideal for boxing, kickboxing, and MMA training.
Pros:
- Absorbs impact well
- Won’t settle as unevenly as other fillers
- Long-lasting and moldable
Cons:
- Can compact over time if not packed properly
2. Sand or Sandbags
Some bags include sand to increase weight and density. Rather than filling the whole bag with loose sand (which can settle to the bottom), many manufacturers use small sandbags placed inside a textile-filled bag to prevent hard spots.
Pros:
- Makes the bag heavier and more stable
- Great for power training
Cons:
- Can create “dead zones” or overly hard spots if not positioned well
- Not ideal for beginner strikers
Pro tip: If you're filling a bag yourself, never fill it with only sand. It’ll turn into a brick over time.
3. Water
A growing number of punching bags, especially free-standing or hybrid bags, use water as their core filling. The water provides natural resistance and simulates the feeling of hitting a human body.
Pros:
- Excellent shock absorption
- Easy to adjust weight (just add or remove water)
- Minimal noise on impact
Cons:
- Requires maintenance (leaks, freezing in cold climates)
- Can feel “splashy” or unstable during kicks
4. Foam
Foam is often used with other fillers, especially in uppercut or angle bags or as a liner. It adds uniformity to the striking surface and helps maintain the bag’s shape.
Pros:
- Smooth hitting surface
- Reduces risk of injury
Cons:
- Doesn’t offer the same resistance as textile or sand
Bells of Steel’s Heavy Bag Set, for example, comes pre-filled with sand, cloth, and EPE foam, creating a firm but forgiving bag that’s perfect for all levels.
Which Filling Is Best for You?
- For Beginners: Go with a textile-filled bag like Bells of Steel’s — soft enough to protect your hands but dense enough to train seriously.
- For Power Strikers: Consider a heavier option with internal sandbags for that grounded feel.
- For Multi-Sport Athletes: A water-filled or hybrid bag might offer the versatility you need.
Ultimately, the best punching bag filler aligns with your training style, impact tolerance, and space constraints.
Final Thoughts
What’s inside your punching bag greatly affects the practicality of your training. Whether you're just getting started with boxing or adding a conditioning tool to your home gym, understanding the different types of fillers can help you make a smarter, longer-lasting investment!
