Hypertrophy - The Biggest Gains Ever Reported

In a series of studies using a flywheel ergometer impressive muscle gains were observed in just 5 weeks. All these studies were performed using untrained subjects exercising the knee extensor muscles (quadriceps).

In one study, ten middle-aged (30–53 years) men and women performed unilateral (left limb) knee extensions two or three times weekly for 5 weeks (1). The right limb was used as a control. They used magnetic resonance imaging (MRI) to measure the volume of individual knee extensor and ankle plantar flexor muscle.

After 5 weeks quadriceps muscle volume increased by 6.1 %. Of note, muscle hypertrophy in the three women examined was of similar magnitude (mean 5.8%) as the mean group response (6.1%).

Body fat percentage calculated from multiple (biceps, triceps, suprailiac and front thigh) skinfolds was unchanged after 5 weeks.

Another study assessed the early changes in muscle size and architecture during a 35-day high-intensity resistance training (RT) program (2). Seven subjects performed bilateral leg extension three times per week on a gravity independent flywheel ergometer.

A significant increase in cross-sectional area measured with MRI was observed in the order of 6.5 % and 7.4 % for two regions (C and D) of the quadriceps; fascicle length and pennation angle also increased by 9.9 % and 7.7 % for those two regions respectively.

This study also show for the first time that changes in muscle size are detectable after only 3 wk of RT and that remodeling of muscle architecture precedes gains in muscle CSA. After 20 days of training there was already a 3.5 and 5.2 % increase in the C and D regions, respectively, along with a 2.4 % increase in fascicle length from the 10th day of training.

These results were replicated once again using the same method and intervention, this time using 15 untrained men divided into 2 groups (3). While eight men were assigned to training using a weight stack (WS) machine, seven men trained using a flywheel (FW) device. Again, volume of all individual quadriceps muscles was determined by magnetic resonance imaging.

Quadriceps muscle volume increased by 6.2 % for the flywheel group vs. 3 % in just 5 weeks.

Another study included 58 subjects and divided them into 2 groups, one using just the mass of the flywheel (19.4 kg) T0 and another using an additional 10 kg on the flywheel (T10).

Subjects were trained but not resistance trained, they had a high physical activity level before and during study, and exercised for a total of 225 min/week, including soccer (90 min/week), swimming (45 min/week), gymnastics (45 min/week), and athletics (45 min/week).

In T0 and T10, respectively, there was a “muscle mass” increase of 9.8% and 15% in just 5 weeks (4)! However the method used to measure body composition was bioelectrical impedance which is not the best method, even if subjects were asked to maintain a normal state of hydration before measurement and they were not allowed to exercise, eat, or drink alcohol or caffeine for 12 hours preceding measurements (in the morning).

Even if the “real” results were... let’s say +5 % increase in muscle mass (I believe lean total body mass and not “muscle mass”) in just 5weeks it would still be incredible, let alone 9.8 and 15 % in just 5 weeks!

Other studies without the use of a flywheel also produced good gains.

Kawakami et al. (5) using MRI found that Triceps brachii CSA increased by 31.7 % (0.28 % per day) after 16 weeks of high-intensity (80 % of 1-RM, 3 days a week) unilateral elbow extension (French press) exercise training.

A study compared a periodic resistance training (PTR) program with a continuous resistance training (CTR) for 24 weeks (6). Both groups performed high-intensity, free-weight bench press exercise training 3 days per week at 75 % RM and training volume was set at 3 sets of 10 reps (with 2–3 min rest between sets).

After the 24-week training period, the rate of average increase in TB-CSA and PM-CSA was 0.13 and 0.22 % per day, respectively (9). This translated itself into 21.4 and 39.4 % for the CTR group and 19.6 and 36.1% for the PTR group, for TB-CSA and PM-CSA respectively.

Another study found an increase of 5kg in lean body mass and a decrease in body fat percentage of 2.4 %, measured with skinfolds, following 20 weeks of training (7). The training program consisted of 2 days per week of three sets of 6-8RM in squats, vertical leg presses, leg extensions and leg curls. 

Women also experience great and rapid muscular adaptations in response to only eight sessions of back squat and deadlift training. Significant increases in lean mass for the combined gynoid and leg regions with +0.68 kg LBM after  just 2 weeks  for  the low  volume, and  +0.47 kg for the  moderate volume within three weeks (8)

Thankfully we have individual data which is more telling of what can happen:

Take notice of the cluster between 1 and 1.5kg and the ones up there at 2kg and even one close to 3kg in just 3 weeks. (Individual subject data points represent the largest absolute change in gynoid + leg (left) and leg (right) lean mass, regardless of the testing session). 

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1. Tesch, PA, Ekberg, A, Lindquist, DM, Trieschmann, JT. Muscle hypertrophy following 5-week resistance training using a non-gravity-dependent exercise system. Acta Physiol Scand 180: 89-98, 2004
2. Seynnes, OR, de Boer, M, Narici, MV. Early skeletal muscle hypertrophy and architectural changes in response to high-intensity resistance training. J Appl Physiol 102: 368-373, 2007.
3. Lena Norrbrand, James D. Fluckey, Marco Pozzo, Per A. Tesch. Resistance training using eccentric overload induces early adaptations in skeletal muscle size. Eur J Appl Physiol (2008) 102:271–28
4. Mariusz Naczk, Alicja Naczk, Wioletta Brzenczek-Owczarzak, Jarosław Arlet, Zdzisław Adach. Impact of inertial training on strength and power performance in young active men. J Strength Cond Res. 2013 Nov 20
5. Kawakami Y, Abe T, Kuno SY, Fukunaga T (1995) Training-induced changes in muscle architecture and specific tension. Eur J Appl Physiol Occup Physiol 72:37–43
6. Riki Ogasawara, Tomohiro Yasuda, Naokata Ishii, Takashi Abe. Comparison of muscle hypertrophy following 6-month of continuous and periodic strength training. Eur J Appl Physiol (2013) 113:975–985
7. STARON, R. S., E. S. MALICKY, M. J. LEONARDI, J. E. FALKEL, F. C. HAGERMAN, and G. A. DUDLEY. Muscle, hypertrophy, and fast fiber type conversions in heavy resistance-trained women. Eur. J. Appl. Physiol. Occup. Physiol. 60:71-79, 1990. 
8. Matt S. Stock, Kendra D. Olinghouse, Alexander S. Drusch, Jacob A. Mota, Jennah M. Hernandez, Chibuzo C. Akalonu, Brennan J. Thompson. Evidence of muscular adaptations within four weeks of barbell training in women. Hum Mov Sci. 2016 Feb;45:7-22