Every trainee will know the very familiar and downtrodden feeling of stagnation or plateaus in gym progress. The weights have stalled, the reps fail to go up and yet it feels like you make a Herculean effort every time you set foot on the gym floor.
“No Pain, No Gain” is your mantra and you virtually wrote the book on hard work paid in sweat, blood and tears.
SHORT-CIRCUIT IN THE GREY MATTER...
At the epicentre of our very existence is the central nervous system (CNS) comprised of the brain, spinal cord and its neural projections to every contracting muscle fibre in the body. The CNS is one of the most important facets to human physical performance but is often poorly nurtured.
We hear all the time of incredible and seemingly physically impossible superhuman feats of strength, power or endurance. Some time ago, the BBC reported how a young woman involved in a car accident summoned up the strength to lift a car 20 times her own bodyweight to free her trapped friend whilst being severely injured herself (BBC, 2005). Yet, it would seem that no matter how hard we train our muscles, nourish them with the right foods, supplement in just the right amounts and provide the correct rehabilitation, very few of us ever seem to tap into our true potential for strength and performance.
Prior to this our muscles tend to experience the proverbial white flag of neuromuscular fatigue. It’s the recovery of this system that allows you to keep making progress in the gym and prevents the slip into the darkness of overtraining. We’re all in a continuous race to fight this inevitable decline in strength and power.
Imagine if you could reduce fatigue by only a few per cent? Over the course of a training lifetime, that’s a greater volume of weight lifted, requiring more adaptation by the muscle and, potentially, further gains in muscle mass.
Are these attempts in vain? Or is there a secret method to annihilating the fatigue complex?
THE FATIGUE FALLACY
Even though neuromuscular fatigue has been studied in detail since the late 1800s (Lombard, 1892), only a few principles have ever emerged that characterise the phenomenon fully. Specifically, neuromuscular fatigue is defined as “A decline in the maximal contractile force of the muscle and/or the inability of the muscle to maintain power output” (Williams and Ratel, 2009).
You’re possibly thinking that an answer to this issue is simply to ensure there is enough fuel in the tank in the form of stored energy (muscle glycogen). However, regardless of how well nourished you are prior to exercise, there is up to a 50% decline in power output when a single muscle contracts maximally through electrical stimulation (Stephens & Taylor, 1971) on subsequent bouts of high intensity resistance exercise.
This shows that despite being awash with nutrients, the CNS must have an intrinsic regulatory role in the ability of a muscle to contract again and again.
WEAKNESSES IN THE ARCHITECTURE...
Before we start dissecting the reasons why neuromuscular fatigue even occurs, it’s well worth highlighting the anatomy of the neuromuscular junction (NMJ) and where the kinks in the armour start to arise as our work efforts in the gym start to take a nosedive.
Cast your eyes over Figure 1 (at the end of the article) for a brief overview of how neural transmissions from the brain cause muscle contraction.
See Figure 1
Once the muscle membrane (sarcolemma) receives the neurotransmitter signal to contract from the neuron, a wave of electrical impulses (action potentials) spread down deep channels (T-tubules) between bundles of muscle fibres (myofibrils) to release calcium (Ca++) from storage (sarcoplasmic reticulum) and cause muscle contraction.
See Figure 2
As you can see, fatigue in itself is comparable to a chain of events along the length of this complex neural system; it can arise at any point in transmission from the neuron or propagation of the action potential along the muscle fibre.
A COMMUNICATION FAILURE...
Finnish investigators Hakkinen and colleagues in a fantastic series of studies from 1994 to 2006 highlighted exactly what types of training and intensities were required to induce this issue.
They took cohorts of male and female athletes and subjected them to 10 sets of squats (anyone who’s ever experienced German Volume Training is probably wincing in pain now!) at 70% of their 1-rep max, very similar to what many a gym-goer is probably using right now.
Even when 3 minutes were allowed between sets, maximal force produced had decreased by 47% in the males and 29% in the females across the sets. The investigators also recorded the voluntary neural activation of the athletes (how long the athletes took to execute each repetition of the exercise), showing a similar 49% and 32% decrease in activation of the exercised muscles.
Follow-up experiments by the same team with explosive strength training (40% of 1-rep max but moving the weight as fast as possible) had the same effect on neural activation (decreased) as the former, but to a lesser extent (Linnamo et al. 1998).
Strangely enough, this effect also seems to occur to a greater extent in men rather than women (Hakkinen et al. 1994, Linnamo et al.1998, Avin, K.G. et al. 2010). Whilst the effect seems to be muscle group-specific, overall, women appear to be more resistant to neuromuscular fatigue than their male counterparts. Perhaps you should think twice before uttering the phrase “you lift like a girl”!
SO FOR HOW LONG DOES THIS NEURAL FATIGUING EFFECT LAST FROM A TYPICAL GYM SESSION?
Training at 100% effort for a single session of resistance training (to muscle failure) has been shown to take anywhere between 24 to 48 hours to fully recover performance (Hakkinen, 1994, Raastad & Hallen, 2000). Add in traditional shock tactics such as forced repetitions and you’ll add another drain on the neural network, prolonging your recovery further (Ahtianen et al. 2003).
Keep this up for weeks on end and you’ll soon see those training log entries stall faster than traffic out of London on a bank holiday weekend.
THE RESEARCH ROUND-UP
The science gives us several reasons why constantly thrashing yourself in the gym will eventually take its toll.
- Lifting with a greater force (i.e. more weight in the lower rep range) requires a significant increase in neural firing at the neuromuscular junction. This is known as high frequency stimulation. This pattern of stimulation requires significantly more time for the CNS to recover than low frequency stimulation activities (e.g. walking or lifting a very light object) (Allen et al. 2008).
- Changes in the proportion of high energy and inorganic compounds in the muscle tissue (e.g. phosphocreatine, calcium, inorganic phosphate, glycogen), an increase in muscle temperature and a concomitant build-up of metabolic byproducts from exercise (such as lactic acid) directly affect the contractile “machinery” (myofilaments) of the muscle cell (Lambert et al. 2005, Pires et al. 2011, Wim & Gijsbertus, 2009).
- A lack of provision for recovery periods within a training programme. Classically, athletes would have their training structured or periodised, according to their goals in a specific training year leading up to a competition. For the average trainee, intensity should be backed off in blocks to allow neuromuscular recovery otherwise this will quickly lead to a decline in performance (Verkhoshansky & Siff, 2009).
So now we’re aware of the detrimental effects of too much training on our gym efforts, are there any nutritional tactics we can utilise in our quest for pivotal neural health? Well, one aspect that is well-evidenced is hormonal balance.
Research is showing that a healthy hormonal profile, in particular the balance between testosterone and cortisol, may induce favourable neuromuscular recovery adaptations (Crewther et al. 2011).
Testosterone is well-known for its anabolic effects on skeletal muscle mass, leading to growth and maturation of both contractile muscle fibre (Kadi, 2009) and storage of glycogen (Lane et al. 2009). Its multiple physiological roles in muscular adaptation have contributed to its elevation to the status of king of hormones in sports performance.
However, one of its lesser known properties is its effects on the CNS. It would appear from animal studies that testosterone provides trophic (cellular) support to the neural network, acting in a neuroprotective manner due to its free movement across the blood:brain barrier (Bialek et al. 2004).
Cortisol, on the other hand, is a catabolic hormone. Whilst it remains within a healthy hormonal range, it has a very definite role to play in dynamic conjuction with testosterone. It is released in response to stress (exercise is a known “stressor”), providing energy to muscle tissue and hence sparing precious protein from catabolic deterioration.
Since the two hormones can be easily tracked and assayed using saliva samples, this pivotal balance may even become the new paradigm for monitoring athletes’ tolerance and recovery from their training programmes (Crewther et al. 2011).
Could the future of truly personalised training programmes be in your spit? It may well be.
NOURISHMENT AND TACTICS TO ALTER THE BALANCE
Shifting that testosterone:cortisol ratio too far in the wrong direction could deliver a fatal blow to those hard-earned muscle gains. There are ways to maintain the balance and push your training recovery into anabolic mode:
- Get serious about sleep. Aim for 6 to 8 hours of sleep per night as a regular schedule. A deficiency of even a week’s worth of rest will crush the king of hormones (Leproult et al. 2011).
- Get lean but don’t crash-diet. Having a bodyfat percentage within the healthy to lower range (10% to 15%) is superb for boosting testosterone levels (Blouin et al. 2007). However, extreme energy restriction (i.e. crash dieting) causes a cataclysmic decline in testosterone and a nice boost to cortisol. Not a good combination. Try to plan ahead and give yourself time to drop the excess blubber slowly (0.5 kg to 1.0 kg per week).
- Carbs to cure. Carbohydrates are often vilified but for the purposes of endocrine health, there couldn’t be a better tool. Low carbohydrate diets (<30% intake) are associated with a low free testosterone to cortisol balance (Lane et al. 2009); but if you keep those carbohydrates in your diet and supplement them during training with essential amino acids (EAAs) you’ll reduce protein degradation and keep cortisol at bay (Bird et al. 2005).
- Bring up the D. Emerging as the undisputed vitamin of choice for all-round health improvements, vitamin D status is also intrinsically linked to high serum free testosterone levels (Wehr et al. 2010). Getting enough of the sunshine vitamin is difficult, especially during the winter months but you can find this fat-soluble wonder vitamin in foods such as salmon, whole eggs and fortified breakfast cereals.
THE TOP 6 TIPS FOR MAKING IT ALL WORK
- In order to increase muscle mass, there’s an extremely strong relationship between the amount of overall force a muscle can exert and its cross-section area (overall size); heavy resistance training will do this (no surprises there). Pretty much every trainee knows at some stage they must get stronger over time to have the best physique changes.
- Continuous heavy resistance training (10 reps or below) will produce significant strength improvements but will also cause a rapid onset of neuromuscular fatigue. This gets worse the heavier the weight becomes and subsequently the reps decrease (e.g. pyramid-style training). Add in forced reps, strip sets and a bit of “you go, I go” and you’re eating into your natural ability to recover.
- Day in, day out heavy loading in the gym very quickly leads to stalling, causing frustration and lack of progress. However, most trainees are looking in the wrong places. The main source of fatigue is within the ability of the athlete to induce neural activation of the muscles. So cycle your training in blocks (e.g. 6 to 8 weeks) with periods of lower intensity lifting, then return to your strength progression work.
Nutrition and recovery
- Diets don’t work and often promote a poor ability to recover the CNS and endocrine system from consistent training. Changes in your physique take time, so plan ahead, try to keep your waistline in check and stay ahead of the rest.
- Fast-acting carbohydrates and essential amino acids taken during training could help maintain training intensity and have a beneficial effect on your recovery outside the gym.
- Try not to skimp on the basics. A good night’s rest will do wonders for CNS health.
Developing a balance between training intensity and recovery so as to make progress without frying your CNS is a tricky task, but it just goes to show that the training journey truly is about “brains” and not “brawn”. M&F
Rick Miller is an HPC Registered NHS Dietitian and works with elite natural bodybuilders on both the training and nutrition aspects of their programmes. Rick holds a BSc with Honours in Human Biology from St Andrews University, a Masters Degree in Sport and Exercise Nutrition from Loughborough University, and, a Postgraduate Diploma in Dietetics from Leeds Metropolitan University. If you have any questions for Rick, please contact him at firstname.lastname@example.org
British Broadcasting Company News (2005). Woman Lifts 20 Times Her Body Weight,[Online]. Available: http://news.bbc.co.uk/1/hi/england/wear/4746665.stm.
Allen, D.G., Lamb, G.D. & Westerblad, H.(2008) Skeletal Muscle Fatigue: Cellular Mechanisms. Physiology Review, 88, p.287-332
Andersson, H., Raastad, T., Nilsson, J.,Paulsen, G., Garthe, I. & Kadi, F. (2008) Neuromuscular Fatigue andRecovery in Elite Female Soccer: Effects of Active Recovery. Medicine & Science in Sports &Exercise, 40(2), p.372-380
Ahtianen, J.P., Pakarinen, A., Kraemer,W.J., & Hakkinen, K. (2003) Muscle Hypertrophy, hormonal adaptations andstrength development during strength training in strength-trained and untrainedmen. European Journal of AppliedPhysiology, 89(6), p.555-563
Avin, K.G., Naughton, M.R., Ford, B.W.,Moore, H.E., Monito-Webber, M.N., Stark, A.M., Gentile, A.J. & Law Frey,L.A. (2010) Sex Differences in Fatigue Resistance are Muscle Group Dependent. Medicine & Science in Sports &Exercise, 42(10), p.1943-1950
Bialek, M., Zaremba, P., Borowicz, K.K.& Stanislaw, J.C. (2004) Neuroprotective role of Testosterone in theCentral Nervous System. Polish Journal ofPharmacology, 56, p.509-518
Bird, S.P., Tarpenning, K.M. & Marino,F. (2005) Liquid Carbohydrate/Essential Amino Acid Ingestion during ashort-term bout of Resistance Exercise suppresses myofibrillar proteindegradation. Metabolism, 55(5),p.570-577
Blouin, K., Bolvin, A. & Tchernof, A.(2007) Androgens and Bodyfat Distribution. TheJournal of Steroid Biochemistry and Molecular Biology, 108(3-5), p.272-280
Crewther, B.T., Cook, C., Marco, C.,Weatherby, R.P. & Lowe, T. (2011) Two Emerging Concepts for Elite Athletes:The Short-Term Effects of Testosterone and Cortisol on the Neuromuscular Systemand the Dose-Response Training Role of these Endogenous Hormones. Sports Medicine, 41(2), p.103-123
Di Guilio, C., Danielle, F. & TiptonC.M. (2006) Angelo Mosso and Muscular Fatigue: 116 years after the firstcongress of physiologists: IUPS Commemoration. Advances in Physiology Education, 30, p.51-57
Hakkinen, K. (1994) Neuromuscular Fatigue inMales and Females during Strenuous Heavy Resistance Loading. Electromyography and ClinicalNeurophysiology, 34(4), p.205-14
Kadi, F. (2009) Cellular and MolecularMechanisms responsible for the action of Testosterone on human skeletal muscle.A Basis for Illegal Performance Enhancement.British Journal of Pharmacology, 154(3), p.522-528
Lane, A.R., Duke, J.W. & Hackney, A.C.(2009) Influence of Dietary Carbohydrate Intake on the Free Testosterone:Cortisol ratio responses to short-term intensive exercise training. European Journal of Applied Physiology,108(6), p.1125-1131
Lambert, E.V., Gibson, A.C. & Noakes,T.D. (2005) Complex systems model of fatigue: Integrative Homeostatic Controlof Peripheral Physiological Systems During Exercise in Humans. British Journal of Sports Medicine, 39,p.52-62
Leproult, R.& Van-Cauter, E. (2011) Effect of 1 Week Sleep Restriction on TestosteroneLevels in Young Healthy Men. Journal of The American MedicalAssociation, 306(8),p.793-896
Linnamo, V., Hakkinen, K. & Komi, P.V.(1998) Neuromuscular Fatigue and Recovery in Maximal Compared to ExplosiveStrength Loading. European Journal ofApplied Physiology and Occupational Physiology, 77(1-2), p.176-181
Lombard, W.P. (1892) Some of the influenceswhich affect the power of voluntary muscular contractions. Journal of Physiology, 13, p.1-58
Pires, F.O., Lima-Silva, A.E., Bertuzzi, R.,Casarini, D.H., Augusta, M., Lambert, M.I. & Noakes, T.D. (2011) TheInfluence of Peripheral Afferent Signals on the Rating of Perceived Exertionand Time to Exhaustion During Exercise at Different Intensities. Psychophysiology, 48(9), p.1284-1290
Stephens, J.A. & Taylor, A. (1971)Fatigue of Maintained Voluntary Contraction in Man. Journal of Physiology, 220, p.1-18
Verkhoshansky, Y.V. & Siff, M. (2009)Supertraining. Sixth Edition - Expanded Version. Verkhoshansky SSTM.
Wehr, E., Pilz,S., Boehm, O., Marz, W. & Obermayer-Pietsch, B. (2010) Association ofVitamin D status with serum androgen levels in men. ClinicalEndocrinology, 73(2),p.243-248
Williams, C.A., & Ratel, S. (2009) HumanMuscle Fatigue. Taylor and Francis Group. Oxon.
Wim, A. & Gijsbertus, J. (2009) Exerciseand Fatigue. Sports Medicine, 39(5),p.389-422