Switching up your workouts is both physically and mentally beneficial. One caveat, though: You don’t want to skimp on strength training. Not only does strength training help us build muscle, but it also revs our metabolism and protects us from injury so we can live freely and be agile for as long as possible.

“Strength training is beneficial in so many ways beyond aesthetics,” says Dan Giordano, D.P.T., C.S.C.S., co-founder of Bespoke Treatments. “It can boost dopamine and endorphin production, improve cardiovascular health, and slow bone loss.”

This makes strength training even more important as we age. “As we get older, the loss of bone and muscle makes necessary daily activities increasingly tricky,” says Charlee Atkins, C.S.C.S., founder of Le Sweat. And it happens earlier than you think: Around age 30, we all start losing muscle mass, eventually making simple tasks more difficult.

So, yeah, no matter how many candles are on your birthday cake or where you’re at in your health and fitness journey, you’ll do well to rely more heavily on weights—especially if you’re dealing with any of the following four issues.

1. You’re In Pain

Throughout our everyday lives, our body undergoes various types of stress, whether from work, playing with kids and pets, or participating in recreational sports. Often, these stressors leave us in pain. Whether you have joint pain or are constantly plagued by aches, building strength can help you overcome it and move pain-free. “The stronger we are, the more resilient our body is to these stressors and activities,” says Zach Murray, C.S.C.S. “Strength training can improve many factors that may lead to both acute and chronic pain, including poor and repetitive movement patterns, muscle imbalances, and even running efficiency.”

2. You’re Not Seeing The Results You Want

If you never miss an early morning spin class or after-dinner run, you deserve a high-five for living an active lifestyle. But if you’re sticking to a healthy diet and exercising regularly, and you’re still not seeing the physique results you’re after (especially if you want a defined, lean look), it’s a red flag. “If your current workout isn’t giving you the results you want, specifically concerning muscle definition, it’s time to strength train more, or lift heavier weights,” says Atkins.

If you’re doing only cardio or bodyweight moves, or lifting the same old weight as always, your muscles don’t get the stimulus they need to keep adapting and growing. If you want to truly change your physique, you have to continue overloading your muscles with more weight.

3. You’re Feeling Down

While it not may not be a silver bullet for mood disorders, resistance training is associated with a significant reduction in depressive symptoms, according to a paper published in the journal JAMA Psychiatry. “Resistance training has repeatedly been proven to be an effective intervention for decreasing symptoms of mental disorders such as depression, anxiety, and addiction,” says Murray. “Not only do the physiological by-products of strength training—such as increased release of endorphins—help to improve mood, but the very act of getting stronger and achieving physical goals not previously possible can improve confidence and self-image.”

Related: Can Your Diet Make You Depressed?

4. Your Metabolism Is Sloth-Like

Feel like no matter what you do, your sluggish metabolism is holding you back from reaching your weight-loss or fitness goal? Research shows that a regular weightlifting routine can help. You see, for a number of hours after a typical strength-training session, your body continues to use more energy than usual in order to recover. (The process is called excess post-exercise oxygen consumption, or EPOC, but you’ve probably heard it referred to as the ‘after-burn’ effect.)

Related: How Much Do Genetics Factor Into The Speed Of Your Metabolism?

One research study showed that after strength training for 100 minutes, women’s metabolic rates stayed elevated (by about 4.2 percent) for the next 16 hours, resulting in an average of 60 extra calories burned. Sixty extra calories burned multiple times every week can certainly add up over time, increasing the average total number of calories you torch and upping your metabolism.

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