Ever wondered if pushing to absolute muscle failure is necessary for maximum gains? The debate between training to failure and leaving reps in reserve (RIR) has divided fitness enthusiasts for years! In this comprehensive guide, we’ll explore the fascinating science behind muscle failure and help you determine which approach might be best for your specific goals. A recent study in the Journal of Strength and Conditioning Research found that both methods can be effective when programmed correctly—but the devil is in the details. Whether you’re a seasoned athlete or just starting your fitness journey, understanding this crucial training variable could be the key to unlocking your potential.
What is Muscle Failure? Understanding the Physiology
Man, I remember when I first started lifting seriously about 15 years ago. I thought muscle failure meant collapsing on the gym floor after every set! It wasn’t until I started studying exercise physiology that I really understood what was happening beneath the surface.
So what exactly is muscle failure? In the simplest terms, it’s the point where your muscles physically cannot complete another repetition with proper form. But there’s so much more going on physiologically!
When you’re lifting weights, your body recruits motor units (a motor neuron and all the muscle fibers it connects to) in a specific order. It starts with the smaller, endurance-oriented motor units and gradually works up to the larger, strength-oriented ones. This is called the size principle, and it’s fascinating stuff! As you approach failure, nearly all available motor units are recruited, which is one reason some people argue for training to failure.
I’ve experienced different types of muscle failure firsthand. There’s concentric failure, where you can’t lift the weight up anymore (like when I got stuck at the bottom of a bench press – embarrassing!). Then there’s eccentric failure, where you can’t control the weight on the way down (definitely don’t recommend this without a spotter). And don’t forget technical failure, where your form breaks down before your muscles actually give out.
The metabolic response to reaching failure is pretty intense too. Lactic acid builds up, ATP (your muscles’ energy currency) gets depleted, and various hormones like growth hormone and testosterone get a nice boost. I remember checking my heart rate after a set of squats to failure – it was through the roof!
But here’s something I didn’t understand for years: muscle damage itself isn’t the goal, but rather the repair process that follows. When you train to failure, you create microscopic tears in your muscle fibers. Your body then repairs these tears and builds the muscle back stronger – that’s protein synthesis in action! I used to think more damage meant more growth, but now I know it’s way more complicated than that.
One thing’s for sure though – whether you train to failure or not, you need to create enough mechanical tension and metabolic stress to stimulate growth. Finding that sweet spot is what it’s all about.
The Case for Training to Failure: Benefits and Research
I’ll never forget my old training partner Mike who swore by training to failure. “Go hard or go home!” was basically his motto. And to be fair, there’s solid research backing up some of his enthusiasm.
When you push to absolute failure, you’re guaranteeing maximum motor unit recruitment. A study I read in the Journal of Applied Physiology showed that the last few reps before failure recruit those stubborn fast-twitch muscle fibers that have the greatest potential for growth. I’ve definitely noticed this effect in my own training – that burn during those last couple of reps feels different, almost more productive.
The hypertrophy benefits can be significant. Research from Stuart Phillips’ lab showed that training to failure produced similar hypertrophy with lower loads compared to higher loads not taken to failure. Pretty cool, right? I remember being skeptical until I tried a program based on this research and saw decent gains despite using lighter weights than I was used to.
There’s also this incredible mental toughness aspect that I’ve experienced. When you’ve truly gone to failure, you know exactly where your limits are. There’s no wondering “could I have done more?” It’s oddly satisfying, even through the discomfort. I used to hate that feeling, but now I almost look forward to it during certain training phases.
For beginners especially, training to failure can help develop a mind-muscle connection and learn what true effort feels like. I coach some newer lifters, and it’s amazing to see the lightbulb moment when they truly reach failure for the first time. Suddenly they realize their perceived limit was nowhere near their actual limit!
The psychological benefits shouldn’t be underestimated either. There’s something empowering about pushing through when your brain is screaming to stop. I’ve applied this mental fortitude to other areas of my life too.
That said, context matters enormously. Training to failure seems to be most beneficial for isolation exercises, machines, and during specific hypertrophy-focused training blocks. I’ve found that failure training works best for me on exercises where safety isn’t a major concern and when I’m well-rested and properly fueled.
The Downside of Training to Failure: Recovery and Risks
Despite the benefits, I learned the hard way that constantly training to failure isn’t sustainable. About five years ago, I went through a phase of taking every single set to absolute failure. Big mistake! After a few weeks, I was constantly tired, my performance tanked, and I actually got weaker instead of stronger.
The research backs up my experience. Studies show that training to failure dramatically increases central nervous system (CNS) fatigue. Your muscles might recover within 24-48 hours, but your nervous system takes much longer. I didn’t understand this at first – I just knew I felt run down all the time, even though my muscles weren’t particularly sore.
The injury risk is another major downside. Form breakdown is almost inevitable during those last grinding reps. I’ve tweaked my shoulder more than once pushing for “just one more rep” on the bench press. Not worth it! Technical failure (where your form breaks down) should almost always be your stopping point, especially on compound movements like squats, deadlifts, and presses.
There’s also the issue of diminishing returns. Research from Eric Helms and others suggests that the fatigue cost of those last few reps at failure might outweigh the stimulus benefits. I’ve tracked my training pretty carefully over the years, and I’ve noticed that when I constantly train to failure, I can’t train as frequently or with as much volume overall. Since total training volume is a key driver of growth, this becomes counterproductive.
The psychological burnout is real too. Training to failure on every set is mentally exhausting. I remember dreading workouts during that “failure everything” phase I mentioned earlier. Exercise should be challenging but still enjoyable overall!
One particularly interesting study I came across showed that training to failure resulted in greater muscle fiber damage but not necessarily greater muscle growth compared to stopping short of failure. When I read that, it clicked why my “destroy the muscle” approach wasn’t giving me the results I expected.
These days, I’m much more strategic about when and where I implement failure training. Live and learn, right?
Reps in Reserve (RIR): The Scientific Approach
After burning myself out with constant failure training, I discovered the concept of Reps in Reserve (RIR) and it completely changed my approach. RIR simply refers to how many more reps you could do if you had to push to failure. It’s tied to the Rate of Perceived Exertion (RPE) scale, where RPE 10 means absolute failure and RPE 9 means you had 1 RIR, RPE 8 means 2 RIR, and so on.
At first, I was skeptical. How could stopping short of failure possibly be as effective? But then I read a fascinating study by Dr. Mike Zourdos that showed similar strength and hypertrophy outcomes between groups training to failure versus leaving 1-2 reps in reserve. The kicker was that the RIR group experienced less fatigue and recovered faster!
I decided to experiment on myself and started leaving 1-3 reps in the tank on most sets. The results surprised me – not only did my performance improve over time, but I actually started looking forward to my training sessions again. I could train more frequently and with higher overall volume since I wasn’t completely trashing myself each workout.
The physiological explanation makes perfect sense. When you train with 1-3 RIR, you’re still recruiting the vast majority of motor units and creating sufficient mechanical tension for growth, but without the excessive systemic fatigue. It’s like getting 90% of the stimulus with only 60% of the recovery cost. Pretty efficient if you ask me!
One challenge I faced was accurately gauging my RIR – it takes practice to know exactly how many reps you have left. I was way off at first, thinking I had 3 RIR when I actually had maybe 1. Video recording my sets helped a lot with this. Research shows that experienced lifters tend to be more accurate at estimating their RIR, but even they’re not perfect.
The beauty of the RIR approach is that it allows for better long-term progression. When you’re not constantly obliterating yourself, you can add weight or reps more consistently over time. I’ve found this to be especially true for compound movements like squats and deadlifts, where the fatigue cost of failure is highest.
That said, there’s definitely a learning curve. It took me several months of conscious practice before I could reliably gauge my RIR across different exercises and rep ranges. These days, it’s second nature, and I adjust my effort based on how I’m feeling that day – another major benefit of this approach.
Hybrid Approaches: Strategic Implementation of Both Methods
After years of experimenting, I’ve found that a hybrid approach works best for most people, myself included. The key is being strategic about when and where you implement failure training versus RIR.
One approach I’ve had great success with is periodizing failure training throughout a training block. For example, during an accumulation phase focused on volume, I’ll stay 2-3 RIR on most sets. Then during an intensification phase, I’ll incorporate more failure training, especially on isolation exercises. This gives me the benefits of both approaches while minimizing the downsides.
Exercise selection matters tremendously too. I’ve learned to be much more conservative with compound movements like squats, deadlifts, and overhead presses. Taking these to failure not only increases injury risk but creates excessive systemic fatigue. Now I typically stay 2-3 RIR on these movements. However, for isolation exercises like bicep curls, lateral raises, or leg extensions, I’m more likely to push to failure occasionally since the fatigue is more localized and the injury risk lower.
I’ve also found that timing failure sets strategically makes a big difference. For instance, taking only the last set of an exercise to failure can give you some of the benefits without excessive fatigue. Or using intensification techniques like drop sets or rest-pause sets on a single exercise at the end of a workout. My favorite approach is what I call “controlled failure” – pushing to the point where form starts to break down slightly, but not to complete muscular failure.
Different training phases call for different approaches too. When I’m in a fat loss phase and training volume is already reduced, I might incorporate more failure training to maintain intensity with fewer sets. Conversely, during a mass-gaining phase where I’m doing more total volume, I’ll leave more reps in reserve to manage recovery.
The key insight I’ve gained is that failure isn’t a binary concept – it exists on a spectrum. Technical failure, momentary concentric failure, complete muscular failure – they all have different applications and recovery costs. Learning to use the right type of failure at the right time has been a game-changer for me.
I also believe in autoregulation – adjusting your approach based on how you’re feeling that day. Some days, stopping 3 reps short of failure is the smart move. Other days, when everything feels great, pushing closer to failure might make sense. Learning to listen to your body takes time but pays huge dividends in the long run.
Individual Factors: Tailoring Your Approach
If there’s one thing I’ve learned from coaching dozens of clients and tracking my own training for years, it’s that individual differences matter enormously when it comes to optimal failure/RIR strategies.
Training experience is probably the biggest factor. When I was just starting out, occasionally training to failure helped me learn what true effort felt like. But as I’ve gained experience, I’ve found that I can stimulate growth with less proximity to failure and better technique. Research supports this – beginners often benefit from occasional failure training to develop the mind-muscle connection, while advanced lifters can stimulate growth with more moderate intensities.
Age and recovery capacity cannot be ignored either. In my twenties, I could train to failure frequently and bounce back quickly. Now in my forties, I’m much more strategic about it. My recovery just isn’t what it used to be! I’ve seen this pattern with older clients too – they typically do better with higher frequency, moderate intensity approaches rather than infrequent, all-out sessions.
Different muscle groups seem to respond differently as well. My quads and chest can handle failure training pretty well, but my lower back and shoulders need a more conservative approach. I’ve noticed this pattern with many clients too – certain body parts just seem more prone to overtraining or injury when frequently taken to failure.
Nutritional status plays a huge role too. During periods of caloric surplus with plenty of carbs, I can push closer to failure more often. During caloric restriction? I’ve learned the hard way to back off the intensity a bit. The research on this is clear – recovery capacity is directly tied to nutritional status.
Sleep quality is another critical variable. After a week of poor sleep, training to failure is a recipe for disaster in my experience. I track my sleep pretty carefully these days, and I adjust my RIR targets based on how rested I am.
There are also fascinating genetic components at play. Some people seem to respond better to higher intensity, lower volume approaches (failure training), while others thrive on moderate intensity, higher volume protocols (RIR approach). Finding your individual sweet spot takes experimentation and careful tracking.
Even psychological factors matter. Some people are naturally more conservative in their training and need to occasionally push to failure to realize their true capacity. Others (like my younger self) tend to overdo it and need the structure of RIR targets to avoid burnout. Knowing your psychological tendencies can help you choose the right approach.
The point is that there’s no one-size-fits-all answer to the failure versus RIR question. Your optimal approach depends on a complex interplay of factors that are unique to you. This is why cookie-cutter programs often fall short – they don’t account for individual variability.
Practical Application: Creating Your Optimal Strategy
After all this theory and research, let’s get practical. How do you actually implement this knowledge in your training? Here’s what’s worked for me and many of my clients over the years.
First, I recommend establishing a baseline by tracking your typical RIR across different exercises. For a couple of weeks, estimate your RIR on each set, then occasionally take a set to actual failure to check your accuracy. Most people (including myself initially) overestimate how many reps they have left in the tank. This reality check can be humbling but incredibly valuable!
Once you have a feel for RIR, try implementing this simple framework I’ve developed:
For compound movements (squats, deadlifts, bench press, etc.):
- Warm-up sets: 5+ RIR
- Working sets: 2-3 RIR most of the time
- Occasional test sets: 0-1 RIR (maybe once every 2-3 weeks)
For isolation exercises (curls, lateral raises, extensions, etc.):
- Working sets: 1-2 RIR most of the time
- Final set of each exercise: 0-1 RIR is fine if recovery allows
I’ve found this approach gives most people a good balance of stimulus and recovery. But remember, this is just a starting point – you’ll need to adjust based on your individual response.
For progression, I recommend focusing on adding weight or reps while maintaining the same RIR rather than simply pushing closer to failure with the same weight. For example, if you can do 225 pounds for 8 reps with 2 RIR, aim to eventually do 225 for 10 reps with 2 RIR before increasing the weight. This approach leads to more sustainable progress in my experience.
Implementing periodic “deload” weeks where you stay 3-4 RIR on all sets is crucial for long-term progress. I schedule these every 4-6 weeks now, and they’ve been a game-changer for avoiding plateaus and overtraining. I used to think deloads were for the weak – boy was I wrong!
As for specific program design, here’s a simple upper body workout example that incorporates both failure and RIR approaches:
- Bench Press: 3 sets of 6-8 reps, 2-3 RIR
- Rows: 3 sets of 8-10 reps, 2-3 RIR
- Overhead Press: 3 sets of 8-10 reps, 2-3 RIR
- Pull-ups: 3 sets of 6-10 reps, 2-3 RIR
- Lateral Raises: 3 sets of 12-15 reps, first 2 sets 2 RIR, last set to technical failure
- Tricep Pushdowns: 3 sets of 12-15 reps, first 2 sets 2 RIR, last set to technical failure
- Bicep Curls: 3 sets of 12-15 reps, first 2 sets 2 RIR, last set to technical failure
This approach keeps the heavy compound movements more conservative while allowing for some failure training on the isolation movements where the risk/reward ratio is more favorable.
Pay attention to warning signs that your current approach needs modification. Persistent fatigue, decreasing performance, joint pain, or decreased motivation are all signals that you might be pushing too close to failure too often. I’ve learned to view these as valuable feedback rather than obstacles to push through.
Remember that perfect is the enemy of good. You don’t need to nail your RIR estimates perfectly every time – being in the ballpark is sufficient. Some days you’ll accidentally go to failure, other days you’ll leave more in the tank than intended. It all evens out over time as long as you’re consistent with your overall approach.
Conclusion
Training to failure and utilizing reps in reserve both have their place in an effective resistance training program. The science suggests that a strategic approach combining both methods may be optimal for most lifters. Remember that your individual response, recovery capacity, and goals should dictate your approach. Consider experimenting with different protocols to find what works best for your body while monitoring your progress closely. Safety, sustainability, and progressive overload should remain your priorities regardless of which method you choose. What’s your experience with these training approaches? We’d love to hear about your results in the comments below!
