Facts About Lean Muscle and Body Fat

The body is an amazing organism made up of many different elements, including various types of tissue, bone, organ and fluid. Two of which, lean muscle and body fat, are discussed most often when it comes to exercise and a sustainable lifestyle. We exercise and monitor our nutritional intake to order to build one, lean muscle, while trying to lose the other, body fat (also known as adipose tissue).

How Much Lean Muscle Does the Average Adult Carry?

Skeletal muscle is the most abundant tissue in our body, accounting for approximately 42 percent and 35 percent of body weight in men and women respectively. In other words, an average male weighing 185 pounds has about 78 pounds of lean muscle tissue while a female weighing 140 pounds has approximately 49 pounds of lean muscle tissue. Take muscle and fat out of the equation, and bodyweight still has other constituents like, water, mineral, bone, connective tissue, and organ weight. Speaking of organ weight, did you know the average human heart weighs about 10 oz. while the brain weighs about 3 pounds? That same average male may have, on average, about 25 percent body fat (or 46 pounds of fat) while that average female may have 30 percent body fat (or 42 pounds of fat).

Did You Know this About Lean Muscle…

One of the amazing things about muscle tissue is that it has the ability through regular, progressive, resistance exercise, to increase in size (known as muscle hypertrophy). Donnelly and colleagues have reported that strength training studies (lasting from 8 to 52 weeks) have shown increases of 2.2 to 4.5 pounds of muscle mass. In addition to increasing in size, muscle tissue also gets stronger with prolonged training. A periodized strength training program can elicit changes in endurance capacity, power output and force production while keeping sarcopenia at bay.

Protein stores found in muscle can account for about 30,000 calories of energy. Muscle tissue can contribute approximately 20 percent of the body’s total daily energy expenditure compared to 5 percent for fat tissue (it would be great if we could tap into those fat stores more often).

Lean muscle tissue requires 3-4 times more calories to maintain compared to fat and is important in the process of energy metabolism. A pound of metabolically active muscle tissue requires 5-7 calories per pound to maintain while less active fat tissue, requires only 2 calories per pound.

Finally, muscle plays an important role in the aging process. With advancing age we experience a loss of exercise capacity. This is due to first, to a decline in skeletal muscle mass and strength during aging and then a decrease in maximal oxygen uptake mainly due to a drop in maximal heart rate, according to Henning Wackerhage, PhD, a Senior Lecturer in Molecular Exercise Physiology at the University of Aberdeen.

Did you Know this About Fat…

Fat is found in the body in the form of triglycerides and stored in fat cells which are called adipocytes. According to Coyle, about 50,000 to 60,000 calories of energy are stored in fat cells throughout the body. Fat can also be stored within skeletal muscle cells.

Fat accumulated in the lower body is subcutaneous. While fat in the abdominal area is largely visceral. Where fat ends up on your body is influenced by several factors, including hormones and heredity.

The photo below shows equivalent amounts of fat and muscle. Lean muscle, however, is more dense and takes up one-third less space compared to fat. Five pounds of muscle and fat may in fact weigh the same but that is where the similarities end.

Source: Reddit

One thing is for certain, we typically want more lean muscle and less body fat. Regular strength training is a much needed critical component for everything from health to activities of daily living. Check out some of the many great strength training routines found on Jefit, like the FitBody Plan. Stay strong with Jefit.

References

Marieb, EN and Hoehn, K. (2010). Human Anatomy and Physiology (8th ed.). San Francisco: Benjamin Cummings.

Elia, M. (1999). Organ and Tissue Contribution to Metabolic Weight. Energy Metabolism: Tissue Determinants and Cellular Corollaries. Kinney, J.M., Tucker, H.N., eds. Raven Press. New York.

Donnelly, J.E., Jakicic, J.M., et. al. (2003). Is Resistance Training Effective for Weight Management Evidence-Based Preventive Medicine. 1(1): 21-29.

Wackerhage, H. (2014). Molecules, Aging and Exercise in Molecular Exercise Physiology. Routledge.

Wood, M. (2018). TBC30: 6 Steps to a Stronger and Healthier You. Wicked Whale Publishing.

Coyle, EF. (1995). Fat metabolism during exercise. Sports Science Exchange, 8(6):59.

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The Science Behind the Best Back Exercises

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There are literally hundreds of different exercises to choose from when developing a Jefit strength training program. That number can easily increase to over a thousand when considering all the different exercise variations. The Jefit database, as an example, has more than 1,300 different exercises. Have you ever thought about what the best exercises are or what’s the perfect exercise to choose for a program? One way to choose the best exercise is from an EMG standpoint. In this particular case, we’re going to talk about the best back exercises. Some back exercises are much better than others in terms of muscle recruitment or activation.

Electromyography (EMG) Measurements

Electromyography (EMG) measures the electrical activity of muscles. Usually performed in a research or rehabilitation setting, EMG records the movement of muscle. EMG is based on the premise when a muscle contracts, a burst of electric activity is generated. The higher the load, the higher the firing rate. Muscle contraction strength is related to the number of motor units in the muscle. Finally, here is a definition of EMG from John Hopkins Medicine. EMG “measures muscle response or electrical activity in response to a nerve’s stimulation of the muscle.”

How do Muscles Move?

Movement actually begins in the brain, specifically with the motor cortex, where neural activity signals the spinal cord, and information about the movement is conveyed to the relevant muscle by way of motor neurons. We can fast forward a bit, a muscle then contracts and produces movement. As muscle fibers contract, they shorten, performing a concentric contraction. Conversely, when muscle fibers lengthen, an eccentric contraction is performed.

A question for you. Can you manage more weight doing a bicep curl when lifting the weight up (concentric contraction) or when lowering the weight (eccentric contraction)? The answer is, you’re stronger during the eccentric phase, where you can actually handle 1.75 times more weight! In addition, 3% more muscle hypertrophy is produced over time during the eccentric phase.

Best Back Exercises Based on this Criteria?

The largest muscle groups that make up the back include the trapezius and latissimus dorsi. There are other smaller muscle groups as well like the rhomboids. Exercise selection typically depends on what a persons goals are, experience level, and equipment availability. All things being equal, the following exercise list includes some of the best back exercises you can do based on EMG.

One study looked at the EMG activation of various muscle groups while doing Pull-ups and Chin-ups. EMG data showed the highest muscle involvement coming from the latissimus dorsi (117-130% range), and biceps brachii (78-96% range).

Other back exercises with a high EMG output were: Dumbbell Bent-Over Two-Arm Row (93%), One-Arm Dumbbell Row (91%), T-Bar Row (89%), Lat Pull-down (86%) and Seated Pulley Row (83%) rounded out the highest EMG activity. Other research on performing a lat pull-down to the sternum with a light lean back also worked well (101%).

There are other exercises, like the Squat and Deadlift that focus on hips and legs but also recruit many other muscle groups, like the back. Both are considered great total-body exercises but the back is used more as a stabilizer than a prime mover compared to a Bent-over Row or Pull-up.

You now have a few back exercises, ranked by science, that you can hopefully start to use more often in your Jefit workouts. Stay Strong!

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