Evidence Based Recovery (Part 3): Acupuncture, Ultrasound, Electrical Stimulation, Laser Therapy and Hyperbaric Oxygen

 
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Evidence Based Recovery (Part 3): Acupuncture, Ultrasound, Electrical Stimulation, Laser Therapy and Hyperbaric Oxygen

In our two previous posts of evidence based recovery, Part 1 covered massage therapy, foam rolling and stretching and Part 2 covered compression garments, heat and ice. In part 3 of the our review of recovery modalities, we will cover acupuncture, ultrasound, electrical stimulation, laser therapy and hyperbaric oxygen.

Acupuncture. Acupuncture is a treatment modality in which thin needles are inserted into the body for therapeutic purposes. It originates from China more than 2,500 years ago and remains a key component of traditional Chinese medicine to treat a wide variety of ailments. In western cultures, it falls under the category of complementary and alternative medicine. Studies have linked acupuncture to reduced cardiovascular disease and hypertension, among other chronic diseases (WHO, 2003). In athletes, acupuncture has been reported to help with exercise performance and recovery. Acupuncture is generally considered to be safe when performed by a trained practitioner using clean and single use needles. Although traditionally it involves only needles, some practitioners may apply a small electric current, a modality termed ‘electroacupuncture.’ Acupuncture should not be confused with dry needling. Dry needling is used by physical therapist with a very different training background to treat musculoskeletal trigger points.

How acupuncture works is unclear. According to traditional chinese medicine, acupuncture addresses an imbalance in the qi, or life force that every person has, that flows within the body. The imbalance or disharmony is sometimes attributed to the yin and the yang or meridians as well. There is no scientific research to support these explanations of acupuncture and they are not based on any known mechanism of action supported by science. Scientific explanations may include activation of the sympathetic and parasympathetic nervous system, promoting gastric peristalsis and exerting anti-inflammatory effects.

There is a dearth of studies evaluating acupuncture as a recovery modality. Three studies show positive results. In a study of recovering basketball players, acupuncture at the Neiguan (PC6) and Zusanli (ST36) acupoints had lower HRmax, VO2max and blood lactic acid than both the sham acupuncture group and control group in a subsequent treadmill test (Lin, 2009). In a subsequent study of basketball players, acupuncture at the Neiguan (PC6) and Zusanli (ST36) acupoints again showed a decrease in serum lactate levels following exercise (Tandya, 2018). Pain perception, but not mechanical pain threshold or maximum isometric voluntary force, improved when acupuncture was applied in the subsequent 72 hours following exercise (Hübscher, 2008). Not all studies on acupuncture show benefit. Dry needling was equivocal to placebo in improving post-exercise hamstring and gluteal pain and tightness (Huguenin, 2005).

In conclusion, acupuncture is complementary and alternative medicine technique that has several barriers to confidently recommend as a recovery modality. The lack of scientific explanation for how the treatment works continues to create challenges for basic science and clinical research. However, the overall lack of research makes any recommendation limited. There are 3 small studies which are positive and one small study which showed no difference. There is an opportunity for further investigation of acupuncture as a recovery modality and it is generally considered safe in the hands of a trained acupuncturist. However, at this time it can not be recommended with confidence as a method to help athletes recovery from exercise or sport.

Ultrasound. Ultrasound has been promoted as a potential treatment modality for muscle injury, for both pain relief and muscle regeneration (Delos, 2013). Despite its widespread use, including by more than 80% of physical therapists, there are no clear indicators that it enhances recovery from activity or injury. The scientific explanation of how ultrasound provides healing benefits is unclear. Early research showed that ultrasound promotes satellite cell proliferation, but the clinical significance of that was unclear (Rantanen, 1999). In individuals with skeletal muscle injuries, adding ultrasound to exercise did not improve recovery compared to exercise alone (Markert, 2005).

There are multiple studies investigating ultrasound as a recovery modality, most of which find no benefit. In a study of athletes performing knee extensions, no differences were noted in peak torque or DOMS at 24, 48, 72 or 96 hours with the use of ultrasound when compared to placebo (Plaskett, 1999). In a similar study of eccentric bicep exercises at 24, 48, 72 and 96 hours, ultrasound did not influence recovery (Tiidus, 2002). Pulsed ultrasound did not affect recovery from DOMS in athletes undergoing eccentric elbow exercises (Shankar, 2006). In contused muscles, ultrasound does not hasten or improve the regeneration of skeletal muscle (Wilkin, 2004). In patients with rotator cuff disease, ultrasound yielded no additional efficacy to the standard physiotherapy treatment regimen (Analan, 2015).

In athletes using a wearable ultrasound device, lactate clearance was faster compared to controls during the first few minutes, however there was no significant difference at 10 and 60 minutes following exercise (Rakiweicz, 2014). In a separate study, wearable ultrasound improved post-exercise lactate clearance (Langer, 2017). One study showed positive effects. In athletes who used ultrasound as a warm up modality, the ultrasound group had less swelling and muscle damage when compared to controls and heat therapy groups (Evans, 2002).

In conclusion, ultrasound has little evidence to support its utility as a recovery modality. All of the studies evaluating symptoms in athletes showed no benefit. There are two studies which show some effect on lactate clearance and one on swelling and muscle damage, but the significance of this to the recovering athlete is unclear. Based on the available evidence, ultrasound can not be endorsed with confidence as a recovery modality.

Electrical Stimulation. Neuromuscular electrical stimulation (NMES) involves using low stimulation frequencies which induce contractions comparable to active recovery. Researchers have postulated that this may favor increased blood flow to muscles, improved oxygenation and metabolite wash out following exercise. Submotor stimulation may also have an analgesic effect on muscle soreness. Theoretically, this may reduce microvascular permeability, minimizing protein leakage and also repelling large, negatively charged proteins from the interstitial space. Notably, the evidence supports the use of NMES in recovery from surgery (i.e. quad recovery after ACL or knee replacement) or in stroke patients, thus providing a strong theoretical bases for use in athletes.

The majority of studies show no or minimal benefit from stim. A 2011 study found no benefit of electrical stimulation with DOMS or recovery knee extensor strength (Leeder, 2011). Butterfield et al found stim was ineffective in providing lasting pain reduction and at reducing ROM and strength losses associated with DOMS (Butterfield, 1997). Multiple other studies showed no benefit for DOMS (Feyistean, 2007; Kang, 2015; Tourville, 2006). One study showed that frequency specific microcurrent therapy reduced DOMS at 24, 48 and 72 hours compared to sham therapy, with no difference in pain (Curtis, 2010). The use of transcutaneous electrical acupoint stimulation (TEAS), a form of acupuncture using electrical stimulation as well, was superior to acupuncture alone in enhancing muscle force recovery but had no effect on lactate removal or power following exercise (So, 2007).

A 2011 review of the available research concluded that stim provided some benefit for lactate and CK clearance for DOMS but lacked evidence regarding performance indicators such as muscle strength (Babault, 2011). A subsequent 2014 systematic review of the data concluded that as a recovery modality, there “may be some subjective benefits for postexercise recovery, evidence is not convincing to support NMES for enhancing subsequent performance” (Malone, 2014). A 2013 study found that low-frequency electrical stimulation (LFES) was similar to active recovery in calf muscles following exercise (Bieuzen, 2013). Although stim reduced blood lactate post exercise compared to passive recovery, it was inferior to submaximal swimming (Neric, 2009).

In conclusion, the available data is limited and what is available suffers from methodological flaws. The variability between applications of electrical stimulation also makes interpretation and extrapolation challenging. Nearly all studies, including two systematic reviews found no benefit for performance and limited benefit for DOMS. It may promote lactate clearance, but the clinical significance is not clear. Several studies even suggest stim was equivocal or inferior to active recovery. The research is not compelling to support the use of electrical stem as a recovery modality.

Laser therapy. Low level laser therapy (LLLT) has been used in the treatment of musculoskeletal pain. There have been some positive findings in the treatment of fibromyalgia and cervicalgia. Light-emitting diode therapy (LEDT) is another modality used to treat musculoskeletal injuries. These modalities appear to induce a photochemical effect in cells through absorption of light by photoreceptors, often described as “photobiostimulation” or “photobiomodulation” (Leal-Junior, 2015). The magnitude of the effect is influenced by wavelength, energy density (or fluence), power density, type of injury, and the absorption spectrum of photoreceptor.

LLLT appears to have benefits as a recovery modality. Although not statistically significant, pre-exercise LLLT trended toward improved soreness in athletes after a plyometric exercise protocol (Fritsch, 2016). Miranda et al found a combination of lasers and LEDs increased the time, distance, and pulmonary ventilation and decreased the score of dyspnea during a cardiopulmonary test (Miranda, 2016). Baroni et al found LLLT treatment before eccentric exercise attenuated the increase of muscle proteins in the blood and loss of muscle strength (Baroni, 2010). In a randomized, blinded study applying LLLT to swimmers adductor group after exercise, researchers found a moderate effect on performance and a small effect on CK levels with no difference on lactate levels (Zagatto, 2016). Larkin-Kaiser et al found that when applied to skeletal muscle before resistance exercise, near-infrared light therapy attenuated strength loss (Larkin-Kaiser, 2015). When applied prior to exercise photobiomodulation therapy reduced sensation of perceived exertion with no effect on lactate clearance (Toma, 2018). Although most human research focuses on LLLT prior to exercise, application after exercise also showed benefit in rat models.

LLLT may help with lactate clearance and limiting CK elevation. In a study of volleyball and soccer players, LLLT helped decreased CK and increase lactate clearance compared to sham therapy with no difference in the wingate test (Junior, 2009). Aver Vanin et al found LLLT at 50 J dose increased performance and improves biochemical markers related to skeletal muscle damage and inflammation with no effect on DOMS (Aver Vanin, 2016). Two other studies found no significant effect on lactate clearance (Toma, 2018; Zagatto, 2016)

The systematic reviews are all generally favorable. Borsa et al reviewed the available data in 2013 and concluded exposing skeletal muscle to single-diode and multi diode laser or multi diode LED therapy was shown to positively affect physical performance by delaying the onset of fatigue, reducing the fatigue response, improving postexercise recovery, and protecting cells from exercise-induced damage (Borsa, 2013). In a 2015 systematic review, the authors found that phototherapy increased time till exhaustion and increased the number of repetitions and concluded phototherapy accelerated recovery when applied before exercise (Leal-Junior, 2009). Another 2015 meta analysis concluded phototherapy may preserve tissue against exercise induced muscle damage and speed up recovery when applied before exercise (Vanin, 2015).

In conclusion, photobiomodulation therapy shows promise for exercise recovery, especially when applied prior to exercise. There are several modalities, it is unclear which is superior although one study found low-powered pulsed laser or light was superior to low power continuous or high-powered continuous in exercise recovery (De Marchi, 2017). LLLT may even be better than cold therapy. In a randomized, non-blinded study of athletes, phototherapy was superior to cryotherapy for muscle recovery (De Marchi, 2017). The evidence is compelling to support LLLT as a recovery modality and it can be recommended with confidence for athletes and sports medicine providers.

Hyperbaric Oxygen. Hyperbaric oxygen therapy (HBOT) is administration of therapeutic oxygen, usually at 100% FiO2 at greater than environmental or atmospheric pressure. Typically, you place the patient in an airtight compartment, increase the pressure and administer oxygen. For therapeutic purposes, this is typically done between 60-120 minutes at a time. HBOT is used in medicine for treating illnesses such as decompression sickness, carbon monoxide poisoning and diabetic ulcers. It has been suggested in the literature that HBOT can be used to treat muscle contusions and sports-related injuries (Tiidus, 2015).  

How HBOT works is based of animal models. Theoretically, administration of 100% oxygen at pressures above atmosphere should reduce tissue hypoxia and enhance oxygen delivery to tissues. This can limit edema, cytokine activity, reduce oxidative and free radical damage and promote accelerated healing. HBOT does have some risk associated with use including barotrauma to ears, sinuses and lungs, claustrophobia and oxygen poisoning.

Most studies of HBOT find no benefit as a recovery modality. A 2016 study looking at Brazilian jiu-jitsu athletes found no difference between HBOT and passive recovery with rates of perceived exertion, lactate clearance, CK or liver enzymes (Branco, 2016). Mekjavic et al found that HBOT did not help with DOMS (Mekjavic, 2000). HBOT following eccentric exercise induced muscle soreness did not improve recovery (Germain, 2003). A 2006 cochrane review found similar conclusions and even stated that HBOT may increase interim pain in DOMS (Bennet, 2006).

In addition to not improving DOMS, Babul et al found that HBOT following eccentric exercises had no effect on muscle force, muscle swelling, or CK (Babul, 2004). In high intensity interval training on bicycles, hyperoxia had no effect on peak and mean power output (Sperlich, 2012). HBOT may even be harmful in recovery. One study found that hyperbaric hyperoxia attenuated blood flow compared to other conditions in the study (Casey, 2011). One study found positive results. When administered prior to exercise, HBOT had a minor effect on muscle fatigue after maximal intermittent plantar flexion exercise (Shimoda, 2015).

In conclusion, hyperbaric oxygen therapy as a recovery modality does not appear to have any beneficial effects. When considering the side effects of the hyperbaric chamber and of hyperoxia, HBOT as a recovery modality likely does more harm than good. Furthermore, one study suggested it attenuated blood flow. It is worth noting that some animal models have shown benefit at the cellular level, but this has not translated into human studies. At this time, HBOT should be avoided as a recovery modality for the above mentioned reasons.

Conclusion. Acupuncture as a recovery modality suffers from a lack of studies investigating its utility. Although it cannot be recommended for recovery, it is generally considered safe in the hands of a trained acupuncturist. There are a multitude of studies investigating both ultrasound and neuromuscular electrical stimulation as recovery modalities with the vast majority finding no benefit in the recovering athlete. These can not be endorsed with confidence. Low level laser therapy has compelling data to support its utility as a recovery modality when utilized prior to exercise. It may even be superior to cryotherapy. Hyperbaric oxygen therapy does not demonstrate any benefit to the recovering athlete, and due to the risks associated with hyperbaric chamber and hyperoxia, it should be avoided.

References

[1] Lin, Zen-Pin, et al. "Effects of acupuncture stimulation on recovery ability of male elite basketball athletes." The American journal of Chinese medicine 37.03 (2009): 471-481.

[2] Urroz, Paola, et al. "Effect of acute acupuncture treatment on exercise performance and postexercise recovery: a systematic review." The Journal of Alternative and Complementary Medicine 19.1 (2013): 9-16.

[3] World Health Organisation (WHO). Acupuncture Review and Analysis of Reports on Controlled Clinical Trials. Cervia, Italy: WHO, 2003

[4] Tandya, L., Mihardja, H., Srilestari, A., Kurniarobbi, J., & Kurniawan, A. (2018). Effect of acupuncture on decreasing blood lactate levels after exercise in elite basketball athletes. Journal of Physics: Conference Series, 1073,

[5] Hübscher M, Vogt L, Bernhörster M, Rosenhagen A, Banzer W. Effects of acupuncture on symptoms and muscle function in delayed-onset muscle soreness. J Altern Complement Med. 2008 Oct;14(8):1011-6.

[6] Huguenin, L., Brunker, PD, McCrory, P., Smith, P., Wajswelner, H., Bennell, K. (2005). Effect of dry needling of gluteal muscles on straight leg raise: a randomized, placebo controlled, double blind trial. Br J Sports Med, 39, 84-90.

[7] Plaskett, Carrie, Peter M. Tiidus, and Lori Livingston. "Ultrasound treatment does not affect postexercise muscle strength recovery or soreness." Journal of Sport Rehabilitation 8.1 (1999): 1-9.

[8] Delos, Demetris, Travis G. Maak, and Scott A. Rodeo. "Muscle injuries in athletes: enhancing recovery through scientific understanding and novel therapies." Sports Health5.4 (2013): 346-352.

[9] Rantanen J, Thorsson O, Wollmer P, Hurme T, Kalimo H. Effects of therapeutic ultrasound on the regeneration of skeletal myofibers after experimental muscle injury. Am J Sports Med. 1999;27(1):54-59

[10] Markert CD, Merrick MA, Kirby TE, Devor ST. Nonthermal ultrasound and exercise in skeletal muscle regeneration. Arch Phys Med Rehabil. 2005;86(7):1304-1310

[11] Shankar, Gauri. "Pulsed ultrasound does not affect recovery from delayed onset muscle soreness." Online Journal Of Health And Allied Sciences 5.1 (2006).

[12] Tiidus, Peter M., et al. "Ultrasound treatment and recovery from eccentric-exercise-induced muscle damage." Journal of Sport Rehabilitation 11.4 (2002): 305-314.

[13] Wilkin, L. D., et al. "Influence of therapeutic ultrasound on skeletal muscle regeneration following blunt contusion." International journal of sports medicine 25.01 (2004): 73-77.

[14] Evans RK, Knight KL, Draper DO, Parcell AC. Effects of warm-up before eccentric exercise on indirect markers of muscle damage. Med Sci Sports Exerc. 2002 Dec;34(12):1892-9.

[15] Warden SJ. A new direction for ultrasound therapy in sports medicine. Sports Med. 2003;33(2):95-107. Review. PubMed PMID: 12617689.

[16] Analan PD, Leblebici B, Adam M. Effects of therapeutic ultrasound and exercise on pain, function, and isokinetic shoulder rotator strength of patients with rotator cuff disease. J Phys Ther Sci. 2015 Oct;27(10):3113-7.

[17] Rakiweicz, Teresa. Determination of the Effectiveness of the ZetrOZ Wearable Ultrasound Device (SAM) for the Postexercise Clearance of Lactic Acid. Senior Honors Thesis. SUNY. 12/19/2014.

[18] Langer, M., et al. The Effect of Low Intensity Wearable Ultrasound on Blood Lactate and Muscle Performance after High Intensity Resistance Exercise. Journal of Exercise Physiology. August 2017. Volume 20, Number 4.

[19] Babault, Nicolas, et al. "Does electrical stimulation enhance post-exercise performance recovery?." European journal of applied physiology 111.10 (2011): 2501.

[20] Malone, John K., Catherine Blake, and Brian M. Caulfield. "Neuromuscular electrical stimulation during recovery from exercise: a systematic review." The Journal of Strength & Conditioning Research 28.9 (2014): 2478-2506.

[21] Bieuzen, François, et al. "Positive effect of specific low-frequency electrical stimulation during short-term recovery on subsequent high-intensity exercise." Applied Physiology, Nutrition, and Metabolism 39.2 (2013): 202-210.

[22] So, Raymond CH, Joseph K-F. Ng, and Gabriel YF Ng. "Effect of transcutaneous electrical acupoint stimulation on fatigue recovery of the quadriceps." European journal of applied physiology 100.6 (2007): 693-700.

[23] Leeder J, Spence J, Taylor E, et al. The effect of electrical stimulation on recovery from exercise-induced muscle damage. Br J Sports Med 2011;45:A21.

[24] Butterfield DL, Draper DO, Ricard MD, Myrer JW, Schulthies SS, Durrant E. The effects of high-volt pulsed current electrical stimulation on delayed-onset muscle soreness. J Athl Train. 1997 Jan;32(1):15-20.

[25] Neric FB, Beam WC, Brown LE, Wiersma LD. Comparison of swim recovery and muscle stimulation on lactate removal after sprint swimming. J Strength Cond Res. 2009 Dec;23(9):2560-7.

[26] Feyistean et al. Comparative Study of Stretch Exercises and Electrical Stimulation in the Relief of Delayed-Onset Muscle Soreness. Journal of Clinical Sciences. 2007, 7(2):21-25.

[27] Kang DH, Jeon JK, Lee JH. Effects of low-frequency electrical stimulation on cumulative fatigue and muscle tone of the erector spinae. J Phys Ther Sci. 2015 Jan;27(1):105-8.

[28] Curtis D, Fallows S, Morris M, McMakin C. The efficacy of frequency specific microcurrent therapy on delayed onset muscle soreness. J Bodyw Mov Ther. 2010 Jul;14(3):272-9. doi:

[29] Tourville TW, Connolly DA, Reed BV. Effects of sensory-level high-volt pulsed electrical current ondelayed-onset muscle soreness. J Sports Sci. 2006 Sep;24(9):941-9.

[30] Junior, Ernesto Cesar Pinto Leal, et al. "Effect of 830 nm low-level laser therapy applied before high-intensity exercises on skeletal muscle recovery in athletes." Lasers in medical science 24.6 (2009): 857.

[31] Leal-Junior, Ernesto Cesar Pinto, et al. "Effect of phototherapy (low-level laser therapy and light-emitting diode therapy) on exercise performance and markers of exercise recovery: a systematic review with meta-analysis." Lasers in Medical Science 30.2 (2015): 925-939.

[32] Aver Vanin, Adriane, et al. "Pre-exercise infrared low-level laser therapy (810 nm) in skeletal muscle performance and postexercise recovery in humans, what is the optimal dose? A randomized, double-blind, placebo-controlled clinical trial." Photomedicine and laser surgery 34.10 (2016): 473-482.

[33] De Marchi, Thiago, et al. "Phototherapy for improvement of performance and exercise recovery: comparison of 3 commercially available devices." Journal of athletic training52.5 (2017): 429-438.

[34] De Marchi, Thiago, et al. "Does photobiomodulation therapy is better than cryotherapy in muscle recovery after a high-intensity exercise? A randomized, double-blind, placebo-controlled clinical trial." Lasers in medical science 32.2 (2017): 429-437.

[35] Fritsch, Carolina Gassen, et al. "Effects of low-level laser therapy applied before or after plyometric exercise on muscle damage markers: randomized, double-blind, placebo-controlled trial." Lasers in medical science 31.9 (2016): 1935-1942.

[36] Miranda, Eduardo Foschini, et al. "Using pre-exercise photobiomodulation therapy combining super-pulsed lasers and light-emitting diodes to improve performance in progressive cardiopulmonary exercise tests." Journal of athletic training 51.2 (2016): 129-135.

[37] Borsa PA, Larkin KA, True JM (2013) Does phototherapy enhance skeletal muscle contractile function and postexercise recovery? A systematic review. J Athl Train 48:57–67

[38] Baroni BM, Leal Junior EC, De Marchi T, Lopes AL, Salvador M, Vaz MA (2010a) Low level laser therapy before eccentric exercise reduces muscle damage markers in humans. Eur J Appl Physiol 110:789–796

[39] Zagatto, Alessandro Moura, et al. "Effects of low-level laser therapy on performance, inflammatory markers, and muscle damage in young water polo athletes: a double-blind, randomized, placebo-controlled study." Lasers in medical science 31.3 (2016): 511-521.

[40] Larkin-Kaiser, Kelly A., et al. "Near-infrared light therapy to attenuate strength loss after strenuous resistance exercise." Journal of athletic training 50.1 (2015): 45-50.

[41] Toma, Renata Luri, et al. "Photobiomodulation (PBM) therapy at 904 nm mitigates effects of exercise-induced skeletal muscle fatigue in young women." Lasers in medical science(2018): 1-9.

[42] Vanin et al. “Effect of phototherapy (LLLT and LEDT) on exercise performance and markers of exercise recovery: a systematic review with meta-analysis”. Physiotherapy. (2015): May, 101:1

[43] Assis et al. Effect of low-level laser therapy (808 nm) on skeletal muscle after endurance exercise training in rats. Brazilian Journal of Physical Therapy. (2015)

[44] Mekjavic, IGOR B., et al. "Hyperbaric oxygen therapy does not affect recovery from delayed onset muscle soreness." Medicine and science in sports and exercise 32.3 (2000): 558-563.

[45] Bennett M, Best TM, Babul S, Taunton J, Lepawsky M. Hyperbaric oxygen therapy for delayed onset muscle soreness and closed soft tissue injury (Cochrane Review). In: The Cochrane Library, Issue 1, 2006. Oxford: Update Software.

[46] Germain, G., et al. "Effect of hyperbaric oxygen therapy on exercise-induced muscle soreness." (2003).

[47] Tiidus, Peter M. "Alternative treatments for muscle injury: massage, cryotherapy, and hyperbaric oxygen." Current reviews in musculoskeletal medicine 8.2 (2015): 162-167.

[48] Babul S, Rhodes EC, Taunton JE, Lepawski M. Effects of intermittent exposure of hyperbaric oxygen for the treatment of an acute soft tissue injury. Clin J Sports Med. 2004;13:138–47.

[49] Casey, Darren P., et al. "Hyperbaric hyperoxia reduces exercising forearm blood flow in humans." American Journal of Physiology-Heart and Circulatory Physiology 300.5 (2011): H1892-H1897.

[50] Branco, Braulio Henrique Magnani, et al. "The effects of hyperbaric oxygen therapy on post-training recovery in jiu-jitsu athletes." PloS one 11.3 (2016): e0150517.

[51] Shimoda, Manabu, et al. "Effects of hyperbaric oxygen on muscle fatigue after maximal intermittent plantar flexion exercise." The Journal of Strength & Conditioning Research29.6 (2015): 1648-1656.

[52] Sperlich, Billy, et al. "Effects of hyperoxia during recovery from 5× 30-s bouts of maximal-intensity exercise." Journal of sports sciences 30.9 (2012): 851-858.

[53] Webster AL, Syrotuik DG, Bell GJ, Jones RL, Hanstock CC. Effects of hyperbaric oxygen on recovery from exercise-induced muscle damage in humans. Clin J Sport Med. 2002 May;12(3):139-50.