Does concurrent training attenuate gains in maximal strength, explosive strength, or muscle size? Original paper

Strength training and concurrent training (strength + endurance) led to similar increases both in muscle size and in maximal strength. Concurrent training led to lower increases in explosive strength, but only when the strength and endurance workouts were separated by <3 hours.

This Study Summary was published on January 4, 2022.

Background

A training regimen that includes both strength and endurance workouts (not always on the same day) is called concurrent training.[1] Unfortunately, endurance workouts can reduce the gains (in strength, power, and muscle size) from strength workouts. This “interference effect”, first described in a landmark 1980 study,[2] can be explained by several mechanisms:

  • Reductions in motor-neuron recruitment and motor-unit discharge (a motor unit being the combination of a motor neuron and all the muscle fibers it innervates)[3]
  • Acute fatigue, if a strength workout is performed soon after an endurance workout[4]
  • MPS inhibition caused by AMPK activation following an endurance workout[5]

The study

This was a meta-analysis of 43 controlled trials that compared strength training (ST) with concurrent training (CT; same strength training + endurance training) for ≥4 weeks.

Three outcomes were assessed:

  • Maximal strength (37 trials, 967 healthy adults) was assessed via squats, bilateral leg press, bilateral knee extension, or unilateral knee extension.
  • Explosive strength (18 trials, 478 healthy adults) was assessed via jump height, squat-jump power, leg-press power at 50% of 1RM, or isometric rate of force development.
  • Muscle size (15 trials, 389 healthy adults) was assessed via segmental DXA scan of the lower extremities, thickness of the vastus lateralis muscle, or cross-sectional area of the quadriceps femoris muscle.

Six potential moderators were assessed in subgroup analyses:

  • Age (18–40 vs. >40 years old)
  • Training status (active vs. untrained)
  • Type of endurance workout (cycling vs. running)
  • Concurrent-training frequency (4.1 vs. 6.1 weekly sessions)
  • Concurrent training: timing of the strength and endurance workouts (different days vs. same day vs. same session)
  • Concurrent training: order of the strength and endurance workouts (when performed in the same session)

The results

Increases in explosive strength were smaller in the CT group.

  • This effect was statistically significant only when the strength and endurance workouts took place less than 3 hours apart. (There weren’t enough trials to assess the effect of workout order.)
  • This effect was statistically significant for cycling but not running; however, when the authors excluded a potential outlier study,[7] there were no differences between the cycling and running trials.
  • This effect was statistically significant for low but not high training frequencies; however, when the authors removed the same outlier study,[7] there were no differences based on training frequency.

Increases in maximal strength and increases in muscle size didn’t differ between the two groups.

The big picture

At least two other meta-analyses have assessed the effects of concurrent training on strength and power adaptations.

In a 2012 meta-analysis of 21 controlled trials, strength-only training led to a greater increase in lower-body power and nonsignificantly greater increases in lower-body strength and muscle size. Concurrent training and endurance-only training both increased VO2max.[1]

A 2021 meta-analysis of 27 controlled trials compared people who were trained (i.e., who’d participated in a structured training program for ≥3 months before the intervention), moderately trained (i.e., who were physically active but hadn’t participated in a structured training program for ≥3 months before the intervention), and sedentary.

  • In trained individuals, strength-only training led to greater 1RM increases for squat and leg press.
  • In moderately trained individuals, strength-only training led to nonsignificantly greater 1RM increases for squat and leg press.
  • In sedentary individuals, strength-only training and concurrent training had similar benefits.

When the authors stratified the results, they found that concurrent training attenuated 1RM increases only when the strength workout and the endurance workout were performed during the same session.[8]

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This Study Summary was published on January 4, 2022.

References

  1. ^Wilson JM, Marin PJ, Rhea MR, Wilson SM, Loenneke JP, Anderson JCConcurrent training: a meta-analysis examining interference of aerobic and resistance exercisesJ Strength Cond Res.(2012 Aug)
  2. ^R C HicksonInterference of strength development by simultaneously training for strength and enduranceEur J Appl Physiol Occup Physiol.(1980)
  3. ^K Häkkinen, M Alen, W J Kraemer, E Gorostiaga, M Izquierdo, H Rusko, J Mikkola, A Häkkinen, H Valkeinen, E Kaarakainen, S Romu, V Erola, J Ahtiainen, L PaavolainenNeuromuscular adaptations during concurrent strength and endurance training versus strength trainingEur J Appl Physiol.(2003 Mar)
  4. ^Ben C Sporer, Howard A WengerEffects of aerobic exercise on strength performance following various periods of recoveryJ Strength Cond Res.(2003 Nov)
  5. ^Layne E Norton, Donald K LaymanLeucine regulates translation initiation of protein synthesis in skeletal muscle after exerciseJ Nutr.(2006 Feb)
  6. ^Daniel Garcia, Reuben J ShawAMPK: Mechanisms of Cellular Energy Sensing and Restoration of Metabolic BalanceMol Cell.(2017 Jun 15)
  7. ^J Mikkola, H Rusko, M Izquierdo, E M Gorostiaga, K HäkkinenNeuromuscular and cardiovascular adaptations during concurrent strength and endurance training in untrained menInt J Sports Med.(2012 Sep)
  8. ^Henrik Petré, Erik Hemmingsson, Hans Rosdahl, Niklas PsilanderDevelopment of Maximal Dynamic Strength During Concurrent Resistance and Endurance Training in Untrained, Moderately Trained, and Trained Individuals: A Systematic Review and Meta-analysisSports Med.(2021 May)