Let's be honest: do you really push yourself to the limit during training – or do you just coast along in your comfort zone?
This is precisely where the crux of the matter lies if you want to make real progress: intensity. It determines whether your body builds muscle, gets stronger or your endurance improves.
But don't worry, intensity doesn't mean destroying yourself completely in every workout. It's about training smart and purposefully.
We'll show you how to find the right intensity for your workout and finally see results.
What does intensity mean in training?
In short, intensity is the amount of effort you put into your workout.
But what does that mean exactly? There are different ways of measuring intensity, depending on whether you are lifting weights, doing endurance training or doing HIIT.
In strength training: How heavy is “heavy”? Here, intensity is often measured as a percentage of your 1-RM (One Rep Max) – i.e. the maximum weight you can lift for one repetition. If you lift, for example, 80% of your 1-RM, that's already quite intense, while 5% is rather easy.
During endurance training: Your heart in focus: When doing cardio, the intensity is usually controlled by your heart rate. This is where terms such as zone 2 (moderate intensity) or zone 4 (high intensity) come into play. Another option is a subjective assessment – how strenuous does your training feel right now?
Your body only ever adapts to the level of strain it is subjected to. No strain = no adaptation.
This means that if you never train intensively, your progress will be limited, no matter how often you train.
Why is intensity crucial to my progress?
Intensity is the centerpiece of your training. It determines whether your body is really challenged – and whether it adapts to become stronger, fitter or more enduring.
Without the right intensity, your workout will be, how can we put it, ineffective. But why exactly is it so crucial?
Your body needs a clear stimulus
Activation of muscle fibers
Fat burning
Improved endurance
Your body needs a clear stimulus
Your body is a real adaptation pro. It only reacts when you confront it with something that goes beyond its comfort zone. This is called “progressive overload”.
Without sufficient intensity, your body thinks, “Oh, I already know this, I don't have to change anything.”
Example muscle building: If you always train with the same weights, your muscles get used to them and stop growing.
Activation of muscle fibers
Intensity controls which muscle fibers are activated. Your body has two main types:
Slow-twitch fibers: For slow, enduring movements (e.g. long runs).
Fast-twitch fibers: For explosive, powerful movements (e.g. sprints or heavy lifts).
Fast-twitch fibers are only activated at a sufficiently high intensity – these are the ones that significantly influence your strength and muscle growth.
To build muscle, you need a moderate to high intensity (about 65-85% of your 1-RM). Why? Your muscle fibers have to get micro-tears so that they come back stronger and bigger during recovery.
Insufficient intensity: Your muscles are being used, but not enough to grow.
Too much intensity: You risk overloading and injuring yourself.
The right intensity is the sweet spot that challenges your muscles without overwhelming them.
Fat burning: Intense beats relaxed
Sure, even a light workout burns calories. But when you train intensely, more happens: your body switches on the afterburn effect (EPOC – Excess Post-Exercise Oxygen Consumption). This means that you continue to burn energy even hours after your workout.
Example HIIT: short, sharp high-intensity intervals increase your calorie consumption significantly more than a steady run.
Fun Fact: Even at rest, your body needs energy to process the high stresses. This means that you work more efficiently.
Intensity also plays a crucial role in improving your fitness. If you always run at the same pace, you will last longer, but you won't get any faster. This is where interval training comes in:
Moderate intensity (zone 2): Builds your basic endurance and strengthens your cardiovascular system.
High intensity (zones 4-5): improves your maximum performance and oxygen uptake (VO2 max).
The combination of both is the key to taking your endurance to the next level.
Which intensity suits my training goal?
The intensity of your training is like the accelerator pedal when driving a car: it determines how quickly you reach your goal. But what is the right “speed”?
Muscle building: Challenge, don't overstrain
If you want to build muscle, you need an intensity that challenges your muscles but doesn't overload them.
The sweet spot here is 65-85% of your 1-rep maximum (1-RM) – i.e. a weight with which you can do 8-12 reps.
Why does it work?
Your muscle fibers have to get micro-tears to grow in recovery.
Too little weight won't stress the muscles enough, and too much will make you give up early.
Strength training: Lifting heavy weights, clear focus
For maximum power, you need high intensities – 85-100% of your 1-RM. This is about explosive power and the activation of fast-twitch muscle fibers, which are responsible for fast and strong movements.
What to look out for:
One to five reps per set is ideal here, as your nervous system will tire quickly at high intensity.
Plan for longer rest periods (two to three minutes) so that you can perform at your best in each set.
Fat burning: Short and crisp or relaxed and long
There are two effective ways to do this: High-intensity interval training (HIIT) or moderate training in zone 2. Both variants work, but in different ways:
HIIT: Short, sharp intervals at maximum intensity. For example: 30-second sprint, 60-second rest, 8 repetitions. The advantage: You burn calories quickly and effectively, and the afterburn effect ensures that your body continues to use energy even hours later.
Zone 2: Here you train at 60-70% of your maximum heart rate, in other words, at a pace where you can still hold a conversation. The advantage of this is that your body primarily uses fat as an energy source – perfect for long sessions such as running, cycling or hiking.
Regeneration: Relaxation is also training
Not every training session has to exhaust you. In fact, low-intensity activity (such as easy walking or swimming) is important for active recovery, helping your body to recover and stay fit for the next session.
How can I increase the intensity of my training?
Do you feel underchallenged in your training or are you stagnating in your progress? Then it's time to turn up the intensity.
Here are the best methods for increasing your intensity:
Increase weight: Choose heavier weights that really challenge you.
Increase repetitions: More repetitions or sets provide more volume.
Shorten breaks: Reduce the breaks between sets to increase the load.
Intensity techniques: Use supersets, drop sets or workout formats such as AMRAP or Tabata.
Vary the pace: Slow down movements, especially in the eccentric phase (e.g. when lowering).
Progressive overload: Increase the weight or number of repetitions gradually.
Explosive movements: Incorporate sprints, jumps or dynamic exercises.
Test what works for you and take your training to the next level!
Intensity is the key to your training success
Intensity is one of the most important factors that will help you to progress in your training. It determines whether you build muscle, become stronger or increase your endurance.
But remember: it's not about always pushing yourself to the limit – striking the right balance is what makes the difference. Train smarter, not harder!
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