Actually, it would make as much sense to split this part of the SuppVersity EMG Series in two, if not three individual analyses, as it would to split your leg workout over two if not three days. In practice, however, most trainees go through the grueling torture of the dreaded "leg day", just once a week and thus I will mirror this practice by writing a similarly gruelingly long blogpost on the best exercises for the major
Image 1: The major muscle groups of your legs. Quadriceps, adductors, abductors, gluteus, hamstrings, gastrocnemius & soleus
the quadriceps (red) - powerful extensors of the knee joint;crucial in walking, running, jumping and squatting; strongest and leanest muscle in the human body
the gluteus (yellow) - three muscles that make up the buttocks: the gluteus maximus muscle, gluteus medius muscle and gluteus minimus muscle;
the hamstrings (blue) - comprises the semitendinosus, semimembranosusand the short and long head of the biceps femoris, of which the former extend the hip when the trunk is fixed, flex the knee and medially (inwardly) rotate the lower leg, when the knee is bent, while the latter extend the hip (e.g when we begin to walk), flex the knee and laterally (outwardly) rotate the lower leg when the knee is bent
as well as the "minor" muscle groups of your legs
the adductors (cyan) & abductors (magenta) at the inside and outside of the tighs, and
the gastromenicus (light green) & soleus (highlighter green), the major muscles of your calves
In the end it is the the muscular development of all of them that eventually distinguishes the men from the boys. And by the way, playing football or, here in Germany, soccer, is no excuse for not training your legs!
Chest
Biceps
Back
Core
Legs
Triceps
Shoulders
Navigate the SuppVersity EMG Series - Click on the desired body part to see the optimal exercises.
In view of the sheer amount of information this part of the EMG Series is going to contain, I will, without further elaborations, go right into an analysis of the most effective exercises, as measured by electromyography (10 male resistance-trained subjects, mean age 22y, mean body-fat 13%; data from Boeckh-Behrens & Buskies. 2000) for all the major and supposedly minor muscle groups of your legs. I. The best exercises for the four heads of the quadriceps Those of you who have read any of the previous parts of this series will already be familiar with the idea of "isolation" being more of a shift in which part of a muscle takes the greatest hit and not so much about training a single strain of a complex muscle such as the quadriceps with its (who would have guessed) four heads. If I am talking about "best exercises for the inner, outer or whatever part" of any given muscle - and this goes for the whole EMG series - what is meant by that is a relative increase in intensity in a given part of a muscle over the rest. Always keep that in mind.
Image 2: Turns out the hack squat is the most effective exercise. In that, going deep (50° knee angle) is only slightly more taxing on the quads than the standard and much safer 90° knee angle.
The most effective exercises with standard equipment:
Hack squats, lying on machine, 50° knee angle
Hack squats, lying on machine, 90° knee angle
Squats, barbell, 70° knee angle
45° leg press, 90° knee angle
Squats, barbell, 90° knee angle
Squats, barbell, 40° knee angle
If you take a look at the results in detail (figure 1), you will notice that the differences between the most (hack squats down to a knee angle of 50°) and the least effective exercise (leg extensions) are far from being earth-shattering.
Figure 1: Relative EMG activity of all four heads of the quadriceps during hack squat, leg press, squat and leg extension variations in comparison to barbell squatting to parallel (knee angle 75°); data adapted from Boeckh-Behrens & Buskies. 2000
What I consider of particular importance is that both in the case of the hack- as well as in the case of the "standard" barbell squat, going beyond parallel (knee angle <70°) is not worth the increased risk of injury (cf. figure 2).
Figure 2: Shear and compressive forces during squat exercise measured at different knee angles; expressed as percentage of the sum of body weight + load (data adapted from a compilation in Escamilla. 2000)
While the EMG activity of the quads may be marginally improved in the case of the hack squat (+0.38%), doing one's squats "ass to the ground", as some people like to call it, actually reduces the quad activity by -10.34%.
Image 3: 45° leg press with a hip angle of 85°; the smaller hip angle (compared to the hack squat) translates into a -16% lower activity of the quadriceps femoris (image everkinetic.com)
Did you know that the smaller the angle of your hip joint (this is in most cases equivalent to the more upright you are sitting or lying on a machine), the smaller is the EMG activity of the quadriceps femoris. During the hack squat exercise, for example the angle of your hip joint is ~100°, the 45° leg press facilitates an angle of ~85° and on the seated leg press the angle is only ~50°. While this does not lead to an 1:1 reduction in EMG activity, the latter is in fact, -16% and -22,5% smaller for the 85° and 50° hip joint angles on the respective exercises.
Training the inner and outer part of the quads Now, if you are a bodybuilder, you will probably be trying to build those "teardrops" (for all real experts who have no clue what those gym-bros refer to as "teardrops", this is the m. vastus medialis, cf. image 3), which actually does not so much look like a tear drop, as it sometimes takes shedding a few tears to get it growing. With respect to the m. vastus medialis Boeckh-Behrens and Buskies have to say that
[the inner part of the quadriceps] is maximally activated via variants of the horizontal leg presses / hack squats - either deep [knee angle <70°] with less weight or not deep [knee angle >70°] with more weight - variations in weight and knee angle tend to be equivalent.
So after all, even your "tear drops" benefits most if you just keep doing those exercises that hammer the quads, i.e. all four heads, as a whole. A slightly narrower stance, however, may be advantageous, while the positioning of the feet, i.e. parallel or with your feet pointing outward at a 30° angle seems to be negligible (+/- 0.25%).
Figure 3: Relative EMG activity of the outer part of the quadriceps (m. vastus lateralis) during barbell squat and single legged squat variations in comparison to barbell squatting to 90° knee angle; data adapted from Boeckh-Behrens & Buskies. 2000
Image 4: Inner (vastus medialis), medial (vastus intermedius & rectus femoris) and outer (vastus lateralis) parts of the "quads"
As you can see in figure 3, things are quite different, when it comes to the outer part of the "quads". Whereas the standard squat with high loads provides maximal muscle stimulation of the m. vastus lateralis, even if you do not even go down parallel to the floor (knee angle 70°), doing the "full squat" down to 40° with an appropriately lighter weight takes away -18% of the stimulus. Similar results can be seen for the isolation exercise single legged squats, where likewise the principle for maximal muscle stimulation reads more weight, greater knee angles (not going past parallel) - a principle, which can also help you keep injury free, as long as you do not wrench it as long as it say more weight and a smaller knee angle, in which case it is a safe bet that you would hurt yourself - probably sooner, than later. Training the medial part of the quads In view of what has been said before with regards to the maximal activation of the fashionable "teardrop" muscle, it is not really surprising that the usual suspects, i.e. the hack squat and the leg press are among the most effective exercises for the medial part of the quads, i.e. the m. vastus intermedius and the m. rectus femoris, as well.
Figure 4: Relative EMG activity of the medial part of the quadriceps (vastus intermedius & rectus femoris) during selected exercises in comparison to hack squats to a 50° knee angle; data adapted from Boeckh-Behrens & Buskies. 2000
Figure 4 does yet go to show you that there is one relatively unknown "special exercise" for soccer players, as Boeckh-Behrens and Buskies like to call it, that outperforms even the hack squat. It's basically the leg kick you see the ladies do with those straps attached to their ankles in order to build one of those J'Lo-ish behinds, but in this case you do it the other way around, or, as the authors suggest, "think of kicking a ball". The +19% higher EMG activity compared to the hack squat (similar results have been found for the standard leg extensions vs. squats by scientists from the Marquette University in Milwaukee, Wisconsin; Ebben, 2009), suddenly makes, what you probably regarded as one of those ridicolously girly exercises, look like a worthwile addition to your regimen... well, at least, in case you are one of those rare exceptions who have an underdeveloped rectus femoris ;-)
Speaking of girly exercises... while it certainly is manly to squat 500lbs, it is not advisable to do so on a daily base. Even the strongest men in the world regard their training sessions asexactly that, the "process of developing the bodily vigour and endurance by systematic diet and exercise, so as to fit for some athletic feat" (Oxford English Dictionary, "training"), or, in other words, as the means to an end. Remember: King-size egos rarely built king-size quads.
II. The Best Exercises for The Gluteus maximus
Image 5: Atlantic Fitness' interpretation of what Boeckh-Behrens & Buskies call a "hip pendulum"
If you have already taken a look at the data in figure 5, you are probably now asking yourself what this strange leg curl variety that is supposed to activate the glutes ~2.3x as effective as a deadlift is all about. Those of you who read the core-episode of this series and the information about the best exercises for the erector spinae, in particular, will be familiar with its name, however. In essence, this is a standard leg curl, but instead of pushing your ties into the pad you are lying on, you try to lift them up, i.e. to curl your hips back, and forcefully contract the muscles of your lower back, your gluteus maximus and your hamstrings. If that's too complicated for you or just doesn't feel right, you can still look out for what Boeckh-Behrens & Buskies call a "hip pendulum" (cf. image 5) and use that instead.
Figure 5: Relative EMG activity of the m. gluteus maximus during selected exercises in comparison to deadlifts using a weight that matches your own body weight; data adapted from Boeckh-Behrens & Buskies. 2000
Of the exercises without additional weight, only leg kick variations, particularly if they are done with peak contractions and/or ankle weights, provide appreciable muscle stimuli, the intensity of which is about equal to to the leg kicks on the hip pendulum (cf. figure 4). III. The Best Exercises for the Hamstrings For the hamstrings the good old lying leg curls are what biceps curl are for the two-headed muscle of your upper arm. And, in fact, the results of the EMG measurements by Boeckh-Behrens & Buskies confirm that generations of trainees cannot be wrong. Similar to the concentration curls in the case of the biceps, only the use of intensity techniques, i.e. partials in the stretch position or peak contractions elevates the already phenomenal EMG values of the standard variety of the lying leg curls to 134% and 112% of the activity measured on the reference exercise (cf. figure 5)
Figure 6: Relative EMG activity of the muscles of the hamstrings during selected exercises in comparison to standard lying leg cursl; data adapted from Boeckh-Behrens & Buskies. 2000
Done correctly, i.e. with a leg angle of 100°, the leg or hip lift is the only body-weight exercise that can compete. With <50% of the muscle activity of the standard lying leg curls, hyperextensions, on the other hand, will do little for your hamstring development.
Did you know that doing partials and peak contractions is particularly effective eccentric exercises? On concentric exercises such as the squat, on the other hand, they increase your chance of getting injured and contribute little to the efficiacy of your training. Tip: If you are talking to your gym partner or, god-behold, your clients about these intensity techniques, you better not call them "X-reps "- otherwise you could be charged by some clever business men who know how to relable training techniques that have been around ever since the early days of physical culture in order to monetize on these "revolutionary new training techniques".
Image 6: An adductor machine, as you probably know it from your gym, as well.
IV. The Best Exercises for Adductors and Abductors
As you probably have expected, the adductor and abductor machines that are mostly operated by the female gym members, are the reference exercises to train the muscles on the inner and outer sides of your tighs. Unfortunately the build of these machines varies from one manufacturer to another, so that you can hardly be sure whether or not your adductor machine will produce the same muscular activation as the ones used in the study. The same holds true for the funky hip pendulum machine, the use of which as an adductor or abductor trainer is pretty tricky, anyways.
Figure 7: Relative EMG activity of the adductors and abductors during selected exercises in comparison to the respective machines (since the exact value for the abductor machine was not given by the authors, the latter is an estimation based on the rank of the exercise); data adapted from Boeckh-Behrens & Buskies. 2000
Viable alternatives for these machine based exercises are the cable adduction(moving leg pulled in before the stabilizing leg) and, probably to the surprise of those among you who refrain from doing body weight exercises completely, the side bridge with hip abduction.When you are squatting, on the other hand, only the adductors are significantly involved in stabilizing the movement. To further increase their activity, you can do your hack squats with a wider stance and your toes facing slightly outward (30°), which will increase the load on your adductors and intensify the exercise by +3%. V. The Best Exercises for the Calves While chicken legs are no exception especially in many of the fitness oriented gyms, toothpick calves are becoming more and more the rule, especially among those trainees who love to do their endless cardio sessions on an elliptical. At the same time few people want to spend an adequate amount of time in training their calves. It is thus all the more important to know which exercises are effective and which are not.
Figure 8: Relative EMG activity of the calf muscles during selected exercises in comparison to the standing calf raises; data adapted from Boeckh-Behrens & Buskies. 2000
As you can see, you cannot avoid doing any variety of calf raises unless you are satisfied with a >65% reduction in muscle activity of the calves when you are doing your lying leg curls for your hamstrings. That being said, there are a few tweaks that make the exercises even more effective. The first, thing you can always incorporate are peak contractions and forced contractions in the stretched position. Moreover, it is imperative that you do not actively bend the knees during the seated calf raise (no bouncing!), if you do not want to reduce the muscle activity by -11%. And in a similar vein, you also do not want to mess with foot position, because (surprisingly?) the parallel foot position is the one that activates the inner, as well as the outer part of the m. gastrocnemius maximally (cf. figure 8)!
Figure 9: Relative EMG activity of the m. gastrocnemius with different foot positions; data adapted from Boeckh-Behrens & Buskies. 2000
In that, it is worth mentioning that the overall activation of the calves is maximized during standing and bent-over (donkey) calf raises, while the m. soleus activity is highest when you do seated calf raises.
A rule of thumb with regards to the activation of m. gastrocnemius vs. m. soleus is "maximize knee angle (as in standing calf raises or donkey calf raises) to maximize gastrocnemius, minimize knee angle (as in seated calf raises) to maximize soleus activity". Note: It is nonetheless imperative (especially if you are using higher loads) not to forcefully lockout your knees, in order to avoid injury.
Image 7: "Real men" ain't ashamed of doing donkey calf-raises like Dave Draper and Arnold used to do it ;o)
Last but not least, a short note on the "high reps for calves"-myth. While I do not question that many trainees just don't feel their calves working, if they do not go into the 50+ rep range, this is not due to the anatomy, the fiber type or whatever crazy anomaly of the calf muscle, but simply due to a faulty execution of the respective exercises. Bouncing, not utilizing the full range of motion and insufficient time under tension (1 sec up, 1-2 sec hold, 3 sec down, would be an appropriate way to go), the by far commonest mistake I see in the gym is turning your calf into a toe exercise by not pushing from the balls of your feet, but from the toes. Now guess what, it takes some time until your toes are finally fatigued and your calves get some work to do ... what would you say, maybe 20-30 reps? Hmm... that would mean that of your 50 reps of calf raises 30 are toe raises and the last 20 actually train your calves - does not sound particularly effective, does it? V. Conclusion: Too Much Work for a Single Day! Now, that you have arrived at the end of this concise and yet super-long write-up on leg training, you should actually ask yourself how and why you have hitherto packed all that stuff into a single workout. Well, I guess, after all, this is a very reasonable question. Nevertheless, fitness competitors and body builders alike have demonstrated time and again that a single "leg day" per week can suffice to build spectacular legs. Is this all genetics or are those guys (and, of course girls) spending the whole day in the gym?
Video 1: Arnold leg training compilation; only the strong will survive ;-)
Did you know that Arnold Schwarzenegger, as a teenager took a barbell into the woods, where he and his friends squatted till they couldn't stand. This does not go to say that this would be the way to go for anyone - especially not the drug free weekend warrior who just wants to keep in shape, but leg-day or not, whenever you train your legs you should take a look at your toothsticks and ask yourself "How many sets have I done for chest, biceps and triceps this week?" If you did more for those than your did for your legs, you better add another set of squats.
Well, I guess some of the "pros" actually spend the whole day in the gym, but a lot of dedication aside, most of them also use an array of "special equipment" to make those workouts extra productive. My personal experience, on the other hand, tells me that legs can in fact sustain much more volume than many trainees claim from themselves (cf. "Did you know...", above). Yet, while I would think that it was possible to do at least a single working set of all "optimal" exercises, the "EMG-optimized routine" I am going to suggest below deliberately shifts the focus from those "optimal" isolation exercises to the optimal varieties of those compound movements that have built such incredible powerful 38"+ tighs on which Tom Platz and some other old school bodybuilders were walking through the gym.
Did you know that compound exercises such as squats and deadlifts have been found to increase the hormonal response to strength training? Well, I guess you did. What may however be news to you is that these temporary increments are hardly going to exhibit those steroid-like effects some trainees seem to be expecting. This does not mean that the value of these exercises is overrated (on the contrary!), but rather that the increase in GH or testosterone after an intense squatting workout is corollary to, not causative of the efficiacy of these exercises.
The reason for that is quite simple: While a set of barbell squats may not activate your glutes like the strange hip pendulum, your quads like the Beckham-ish leg kicks and your adductors like the girly adductor machine, it will nevertheless build adequate power and mass in all three of these muscles, fortify your core, your calves, your upper back and even help with conditioning and fat loss. In other word, as gruelling as they may seem compared to some of the machine based isolation stuff, compound exercises will still give you the most bang, in this case muscle and strength gains, for your bucks, i.e. the time you spent and the energy you invest in the gym.
Image 8: As long as you are injury free, there is noo way to get around squatting - one way or another (image everkinetic)
If you cannot do squats use leg press machines instead.
As a beginner always have a qualified trainer show you how to squat.
An EMG-optimized routine There is of course a myriad of ways of combining the individual exercises, my personal recommendation for overall leg development (based on EMG measures) would yet be as follows*:
Squats - to parallel (70°), 6-10 reps
Hack squats - to 90°, 8-12 reps
Leg curls - peak contract. or partials, 10-12 reps Superset:
Donkey calf raise - peak contract., 12 reps
Seated calf raise - partials, 12 reps Optional
Adductor machine - 12-15 reps
Abductor machine - 12-15 reps
You may notice that I do not make volume (i.e. set) recommendations. This is due to the fact that I found that everyone has to find what works best for him / her in terms of optimal volume and training frequency. This may also change over time / according to lifestyle factors / nutrition and supplementation.
You will have heard about "calf shocker" routines, but would you have imagined that it takes electro shocks?
I don't know how often I've been writing about the truth and fallacy of the good old saying "no pain, no gain", here at the SuppVersity. And while it certainly has its merit for the faint-hearted, the notion that "pain" will entail "gain" is fallacious, also because it suggests that allowing for adequate recovery would be inferior to digging a deep black "hole of pain" (suggested read: "The SuppVersity Athlete's Triad Series").
And while I know that you know that this ain't the way to go, I am also honest enough to admit that I often catch myself pondering the incorporation of intensity techniques, additional exercises or some fat burning minutes of HIIT, but rarely thinks about the undeniable benefits of things like the hot baths for pre-regeneration and other means to speed up recovery (learn more) ...
Recovery, ceratinly not the #1 topic for gym-conversations
I am not sure, whether or not today's SuppVersity article on the surprising benefits of electrical muscle stimulation (EMS) during the recovery period is going to change that, but it certainly adds another interesting option to my toolbox. After all, the improvements in strength and the researchers from the Quincy College the University of Texas at San Antonio, the Hospital of the University of Pennsylvania, the National Strength and Conditioning Association and the University of Florida present in their most recent paper in the April issue of Official Research Journal of the American Society of Exercise Physiologists would suggest that it will not just allow me to return to the gym earlier, but will also make me stronger.
The "Marc Pro(TM)" is not just the $650 device used in the study, it is also one of most frequently used words in the study at hand... what? No, there is no conflict of interest declared, but I believe the Journal of the American Society of Exercise Physiologists does not even require that.
The study of which I'd better tell you in advance that is has a slight smack of "product pimping", because it mentions the specific EMS device, the Marc Pro(TM) not just in the methods section, but also in the title (Westcott. 2013), involved two trials with comparably large groups (n=43 / n=62) of male and female subjects in their best years (mean age: 61.3 / 61.7 years).
10 weeks 2x per week full body + 4x per week EMS
Suggested read: "Fast Paced High-Resistant Explosive Circuit Training Burns More Fat and Builds More Muscle Than Classical Weight Training. Trainees Dropped 1.5% Body Fat and Gained 3 Pounds of Lean Mass in 8 Weeks." - Don't discard the value of a fast paced full body resistance training (read more).
During both 10-week trials all participants trained twice a week for 60 minutes. The training comprised a medium-paced circuit training on 13 Nautilus machines including leg extension, leg curl, leg press, hip abduction/adduction, chest press, seated row, shoulder press, lat pull down, low back extension, abdominal flexion, torso rotation, neck flexion/extension and calf press. Each exercise was performed only once and the weight was progressively increased by 1% whenever the subjects were able to perform more than the prescribed number of 8-12 reps at a well-controlled pace of 3s for both the concentric and eccentric portion of the exercise. In addition to the standard strength workout, the subjects performed ~20 min of recumbent cycling at 70 to 80% of predicted maximum heart rate) and ~5 min of major muscle group stretching exercises towards the end of each workout.
While all subjects underwent the same supervised workout program, only 50% of them were assigned to the EMS group, and instructed to self-administer 1h of electrical muscle stimulation to the calf muscles of both legs four times a week. With the two obligatory exercise sessions, this allowed for two "recovery sessions" in-between workouts.
Figure 1: Changes (rel. to baseline) in the EMS and control groups after 10-weeks of training (Westcott. 2013)
As the data from the pre- and post strength 3-RM tests and the results of the fatigue questionnaire, a 9-point rating scale with anchors of 1 (never experience feelings of calf muscle fatigue) and 9 (always experience feelings of calf muscle fatigue) in figure 1 goes to show you this routine was surprisingly effective in both increasing the effective gains in calf muscle strength and decreasing the workout induced fatigue.
So what's the mechanism here?
It is not exactly likely that the medium intensity EMS targets the IGF-1 + muscle growth promoting PGC-1 a4 isoform (learn more)
The exact mechanism for the benefits, the researchers observed in both experiments, is not fully understood, they stand in line with previous research mostly by members of the same research group (Parker. 2003; Kemmler. 2010; Wescott. 2012; DiNubile. 2011; Girold. 2012) which suggests that the application of electical muscle stimulation "causes positive cellular responses such as nitric oxide (NO) production, fluid shifts, protein clearance, and angiogenesis" and allow for the hypothesis that additional, isokinetic contractive stimulus has the potential to induce mRNA transcriptional proteins such as PPAR gamma co-activator (PGC)-1 alpha (learn more) and the vascular endothelial growth factor VEGF.
Against that background, the scientists assumption that [...]the enhanced muscle recovery associated with [...] electrical stimulation may be due to increased microcirculation, muscle loading, and angiogenesis." (my emphasis in Westcott. 2013) appears reasonable and would warrant their conclusion that EMS which is hitherto used mainly by professional athletes (esp. football players) "may also be beneficial for less fit individuals who experience prolonged periods of recovery or uncomfortable levels of muscle fatigue after exercising." (Westcott. 2013)
I openly admit: Hot baths are still not a part or my "pre-recovery" routine, but I like some cheap and effective walking on an incline on the day after a leg workout.
Bottom line: Depite the overall promosing results of the study at hand, I'd still have a few questions as far as (a) the usefulness, (b) the alternatives and (c) the superiority of EMS therapy as a means to accelerate recovery and adaptation actually is. A handful of studies, a shiny website and the argument that it does works in recreational, or as the scientists write "less fit" trainees, as well as in pro-athletes won't make me pay approx. $650 for an "electro shocker". This is all the more true in view of the fact that regular aerobic exercise and HIIT (learn how to set up a routine) will also promote PGC1-alpha and VEGF and could - appropriately dosed - probably elicit similar effects.
Apropos "effects" you should not forget that the parameters the scientists measured are actually both performance parameters. Regardless of the fact that the latter is called "fatigue", the fatigue after a standardized workout is mainly determined by your central and peripheral conditioning. It is thus obvious that you should be able to reduce the post-workout fatigue by any means of additional exercise that does not overtax the system - this may also involve enhanced recovery, but the enhancement is a function of physiological adaptations and not externally applied electrical stimuli.
Against that background, the only advantage of EMS over "conscious", i.e. brain-controlled contractions such as a 3x3min (x2 for each leg) session of single-legged body-weight calf-raises or even a simple walk in the park with a deliberate emphasis on calf-involvement would produce, appears to be that it would ease the burden on the central nervous system. Whether that's essentially necessary for the average trainee is however questionable; and though I would probably be slightly irritated, if you called me "an average trainee", I for my part will stick to some recuperative walking on an incline to promote calf-recovery.
References:
DiNubile N, Westcott W, Reinl G, et al. The Marc Pro TM device is a novel paradigm shift in muscle conditioning, recovery and performance: Induction of nitric oxide (NO) dependent enhanced microcirculation coupled with angiogenesis mechanisms. JEPonline. 2011;14(5): 10-19.
Girold S, Jalab C, Bernard O, et al. Dry-land strength training vs. electrical stimulation in sprint swimming performance. J Strength Cond Res. 2012;26(2):497-505.
Kemmler W, Schliffka R, Mayhew JL, von Stengel S. Effects of whole-body electromyostimulation on resting metabolic rate, body composition, and maximum strength in postmenopausal women: The training and electrostimulation trial. J Strength Cond Res. 2010;24(7):1880-1887.
Parker MG, Bennett MJ, Hieb MA, et al. Strength response in human femoris muscle during 2 neuromuscular electrical stimulation programs. J Orthop Sports PhysTher. 2003:33(12): 719-726.
Westcott WL, Chen T, Neric FB, et al. The Marc Pro TM device improves muscle performance and recovery from concentric and eccentric exercise in duced muscle fatigue in humans: A pilot study. JEPonline. 2011;14(2):55-67.
Westcott W, Han D, DiNubile N, Neric F, Loud RLR, Whitehead S, Blum K. Effects of Electrical Stimulation Using the Marc Pro(TM) Device during the Recovery Period on Calf Muscle Strength and Fatigue in Adult Fitness Participants. JEPOnline. April 2013; 16(2): 40-49.
