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When is the best time to workout to build muscle

Summary of an article looking at an anabolic signaling response to morning (AM) and afternoon (PM) resistance training bout (80% RM).

Who

24 physically active healthy males who did not perfrom resistance training regularly during the last 6 months (UK).

Strength training group
24 males
aged 21.4 (±1.9) years
body weight 83.7 (±13.7) kg
Control group
16 males (randomly selected from 24)
aged 22.0 (±2.0) years
body weight 84.0 (±6.3) kg

Design

Intervention study (non-randomized).

Strength training group

  • 40 minutes (AM session around 8am and PM session around 6pm separated by at least by 72 hours)
  • exercises: seated leg press, chest press, lat pull down, shoulder press
  • 50% 1RM for 2 sets 10 repetitions, 80% 1RM for 3 sets 10 repetitions (2 minutes rest between sets)

Control group

  • 40 minutes
  • of rest

Outcome measures

  • acute anabolic signaling markers: IGFBP-3 (insulin-like growth factor-binding protein-3), myogenic index

  • cortisol (blood sample)

  • temperature (infrared ear thermometer)

  • serum samples were treated on C2C12 mice cell lines

IGFBP-3a protein that binds insulin-like growth factor IGF-1, which has an anabolic effect.

cortisola hormone that among other functions increases muscle breakdown.

myogenic indexa measure of cells acquiring specialization.

Main results

  • Body temperature was higher pre-exercise at PM (37.3°C) than at AM (36.9°C)

  • Pre- and post-exercise cortisol concentration was lower at PM than AM in both groups.

  • Myogenic index was higher (114%) pre-exercise at PM than at AM, but post-exercise myogenic index was higher at AM than PM.

  • Serum IGFBP-3 increased significantly after PM exercise when compared with decrease after AM exercise. No differences were observed in non-exercising group.

  • Post-exercise lactate was higher at PM (6.4mmol/L) than AM (5.8mmol/L)

  • Pre-exercise myotube width was greater at PM compared to AM. No difference in myotube width between groups post-exercise.

  • No difference in pre-exercise serum, glucose level or haematocrit at AM compared to PM

  • Haematocrit and serum changed from pre- to post-exercie both AM and PM.

Take home message

For a clinician
Resitance training at PM may provide better metabolic environment for anabolic effect: higher body temperature, lower cortisol and lactate levels, higher serum IGFBP-3 concentration.
For a parent
Resistance training in the afternoon may provide better metabolic environment to build muscles.
For an athlete
To build muscle, you should move your resistance training to the afternoon.

Original article

Burley SD, Whittingham-Dowd J, Allen J, Grosset JF, Onambele-Pearson GL. The differential hormonal milieu of morning versus evening may have an impact on muscle hypertrophic potential. PLoS One. 2016 Sep 1;11(9):e0161500.

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