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Exercise Choice: The 3 Factors in Choosing the Right Exercise


calendar-iconFebruary 13, 2019

Foundational Training Series


Every exercise boils down to 3 unique factors

  1. Compound vs. Isolation
  2. Unilateral vs. Bilateral
  3. Free weight vs. Machine

Principles of resistance training such as the hypertrophy and progressive overload will utilize these different exercise choices in order to build the best workout routines.

Everyone has their favorite exercise regimen, and the online fitness community is filled with "experts" claiming different sets of exercises are the "best for muscle growth". As a result, anyone trying to build a new workout plan is left dazed and confused after just a couple of Google searches.

What are the best kinds of exercises for muscle growth and fat loss? We'll break it down in simple (and scientifically supported) terms so you can build your best workout programs with exercises that are optimal for your goals.

Compound vs Isolation Exercises

One choice in building your workout is between compound exercises and isolation exercises.

Compound exercises are exercises that work multiple muscle groups at the same time, like the bench press or military press.

Compound exercises are more efficient means of muscle growth because they recruit multiple muscle groups at a time.1-6 This creates greater training volume and intensity, both of which lead to greater muscle growth.1-6

Isolation exercises are exercises that work a single muscle group at a time, like a bicep curl or tricep extension. Isolation exercises can be useful targeting specific muscles for muscle growth, and in stressing muscles that aren't worked directly in a compound exercise.1-6 They can also be particularly useful if one muscle group is lagging behind another and creating imbalances within a compound exercise that relies on the strength of multiple muscle groups.1-6

The addition of single joint exercises to a resistance training program involving multi-joint exercises does not seem to promote additional benefits to trained men, suggesting multi-joint-only resistance training to be a time-efficient approach.

DeFranca et al

In other words, compound exercises and isolation exercises are both great options for contributing to muscle growth.

When choosing between compound and isolation exercises, its best to utilize compound exercises to hit more muscles at once, and use isolation exercises to address more specific muscle growth needs.

Free Weight vs Machine Exercises

In building your training regimen, you'll also be faced with the decision of using free weights or machine exercises. Free weight exercises are exercises where the resistance is provided by a barbell, dumbbells, or any other free moving object, such as a barbell squat or a dumbbell bent-over row. The object being moved is on a free path – no cables, no attachments – nothing. Free weight exercises are useful because they more muscle fibers, which is beneficial for muscle growth.7-9 This is because they require more muscles to control the path of resistance.7-9

Machine exercises are exercises that provide resistance through a fixed path or range of motion, such as a smith machine bench press or leg press machine. Free weight exercises generally lead to greater to muscle stimulation than machine exercises and therefore offer more opportunity for muscle growth.7-9 

Results suggested greater muscle activity during the free-weight bench press, especially at the 60% 1-RM load, although there were notable differences among the patterns of individual subjects.

Steven & Friday

Machines exercises offer their own advantages, though, such as:

  1. Increased safety
  2. Improper form prevention
  3. Greater ease of use.

Machines also allow for the performance of some exercises that are not practically accomplished with free weights. Imagine doing leg extensions with free weights!.10

When choosing between free weight or machine exercises, it's best to utilize free weight exercises to stress your muscles more dynamically, and use machine exercises while learning a new motion or to add more weight to specific motions that are difficult to perform with free weights.

Author's note: Exercises using a cable, like a cable fly or tricep pull-down fall somewhere in between free weight and machine exercises. Incorporating these types of exercises into your workout can also be beneficial!

Unilateral vs Bilateral Exercises

A final choice you'll have to make when choosing the exercises in your workout is between unilateral and bilateral exercises. Bilateral exercises are exercises where you perform a motion with both sides of your body simultaneously, like an overhead press.10-12 Bilateral exercises are useful because they allow you to use greater resistance as both halves of your body can work together more effectively. They are also time efficient – you don't have to take the time to perform repetitions for each side of your body.

Unilateral exercises are exercises you only use one side of your body independent of the other, like a dumbbell lunge or a single arm overhead press. Unilateral exercises can be useful when you have an injury that prohibits the use of an arm or a leg. They also have different levels of muscle activation, which can be useful for progressive overload.10-12

Results indicate that UL and BL are equally effective for early phase improvement of unilateral and bilateral leg strength and power in untrained men and women.

McCurdy et al.

In summary, unilateral exercises are just as effective as bilateral exercises, you won't sacrifice any potential strength gains or muscle growth by doing one over the other.

When choosing between unilateral and bilateral exercises, it's best to use bilateral exercises to save time and lift more weight, and use unilateral exercises when you have an injury or want to add variable muscle activation into your routine.

The Takeaway

The bottom line here is there is no "best type of exercise".

Exercises mix and match from a range of classifications including:

  • Compound exercise – Hits multiple muscle groups
  • Isolation exercise – Hits a single muscle
  • Free weight exercise – Generally uses a barbell or dumbbell a.k.a. no machines
  • Machine exercise – This uses a machine
  • Unilateral exercise – This works a single side of your body
  • Bilateral exercise – This works both sides of your body

For optimal muscle growth and a workout that fits your personal goals, it is best to incorporate all types of exercises into your routine.

Each type of exercise has its own strengths and weaknesses, so by using a wide variety of exercises, you get the best of all worlds!


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  2. Dankel SJ, Mattocks KT, Jessee MB, et al. Frequency: The Overlooked Resistance Training Variable for Inducing Muscle Hypertrophy?. Sports Med. 2017;47(5):799-805. Link
  3. Schoenfeld BJ, Ogborn D, Krieger JW. Effects of Resistance Training Frequency on Measures of Muscle Hypertrophy:
    A Systematic Review and Meta-Analysis. Sports Med. 2016;46(11):1689-1697. Link
  4. Gentil P, Soares S, Bottaro M. Single vs. Multi-Joint Resistance Exercises: Effects on Muscle Strength and
    Hypertrophy. Asian J Sports Med. 2015;6(2):e24057. Link
  5. De frança HS, Branco PA, Guedes junior DP, Gentil P, Steele J, Teixeira CV. The effects of adding single-joint exercises to a multi-joint exercise resistance training program on upper body muscle strength and size in trained men. Appl Physiol Nutr Metab. 2015;40(8):822-6. Link
  6. Gentil P, Fisher J, Steele J. A Review of the Acute Effects and Long-Term Adaptations of Single- and Multi-Joint Exercises during Resistance Training. Sports Med. 2017;47(5):843-855. Link
  7. McCaw ST, Friday JJ. A Comparison of Muscle Activity Between a Free Weight and Machine Bench Press. The Journal of Strength & Conditioning Research. 1994;8(4). Link
  8. Mazzetti SA, Kraemer WJ, Volek JS, et al. The influence of direct supervision of resistance training on strength
    performance. Med Sci Sports Exerc. 2000;32(6):1175-84. Link
  9. Willoughby, Scott D, Gillespie J. A Comparison of Isotonic Free Weights and Omnikinetic Exercise Machines on Strength.; 2018. Link
  10. American College of Sports Medicine position stand. Progression models in resistance training for healthy adults. Med Sci Sports Exerc. 2009;41(3):687-708. Link
  11. Mccurdy KW, Langford GA, Doscher MW, Wiley LP, Mallard KG. The effects of short-term unilateral and bilateral lower-body resistance training on measures of strength and power. J Strength Cond Res. 2005;19(1):9-15. Link
  12. Mujika I, Padilla S. Detraining: loss of training-induced physiological and performance adaptations. Part II: Long term insufficient training stimulus. Sports Med. 2000;30(3):145-54. Link
Date Created: February 13, 2019

Last Updated: April 2, 2020

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