1. What does your heart rate tell you?
Wearing a heart rate monitor can be effective for cardio. Your heart rate should reach three-quarters of its maximum for an effective cardio session (I recommend HIIT for an even more effective cardio session and a longer after-burn). And how do you work this out? Your maximum heart rate is 220 minus your age. Once you have your maximum heart rate, multiply by .75. Aim for this as your best measure of cardiovascular fitness.
2. How quickly do you recover from intense activity?
The more conditioned you become, the faster you will recover. Test yourself by doing 50 jump squats and time how long it takes you to recover. Repeat that test 2 weeks later and compare the length of time it takes you to recover. If it slows quickly and regulates itself, that's a good sign of cardiovascular fitness, which comes as a result of effective workouts.
3. Can you hold a conversation?
Personally, talking during a workout is not my thing. That helps me make sure I am focusing on my reps and therefore having an effective workout. If you work out with a friend and find that you can maintain a conversation throughout your exercise, find a new friend or shut your mouth lol. There's a good chance too much chatting means you're not pushing yourself as much as you can. Find a happy medium which feels challenging, yet sustainable.
4. How are you sleeping?
If you're physically tired the night after a workout, chances are you had a great workout. Exercise should make you fatigued, but again, if you still find yourself tossing and turning, that can be a sign of overtraining. The post-workout hormones may keep you up if you really go at it hard. I find if I workout close to bed time I can't go to sleep easily.
5. Are you focusing on quality over quantity?
You may think going to the gym 6 days a week for 2 hours each day will equal better results. Honestly, that sounds like after a month you'll be burnt out. Making sure your workouts are effective will keep you on track and save time. Train smarter, and you'll save time. After all, we all complain about not having enough time right?
High-intensity interval training is more effective at getting extra calorie burn during and after your workout. The same holds true for compound strength training movements (using more than one muscle at once). If you have an hour or more, hit the weights and then do cardio. Cardio burns carbohydrates first and then fat, so utilize energy from carbohydrates in your body to fuel your strength session, and then move on to cardio where your body will have no choice but to burn fat. Prioritize weights before cardio. Cardio expends more calories during the workout, but may not have as much after-burn.
6. How hungry do you feel after you've worked out?
It's normal to feel hungry after you've worked out. Following a massive expenditure of energy, your body will need to refuel and you may find yourself craving carbohydrates and a substantial meal. This is a sure sign that you've worked hard. But if you had a big meal before you workout (which I don't recommend), you might not be hungry immediately after you workout. Listen to you're body. Don't force yourself to eat if you aren't hungry. Wait and hour and see how you feel.
7. What is your perceived rate of exertion?
I love using the rate of perceived exertion to measure a client's intensity during a workout. The RPE scale defines the rate of perceived exertion "by use of a 0-to-10 chart to rate the feelings caused by your exertion." For example, sitting in front of the TV gets a rating of 0. Increasing pace or adding a hill could have you working more toward a 10 on the scale. Clients I work with usually underestimate their RPE, thinking they're at level 8 when they're really at a 5.
Sources: https://www.huffpost.com/entry/workout-tips_b_3157878