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Hawke F, Sadler SG, Katzberg HD, Pourkazemi F, Chuter V, Burns J. Non-drug therapies for the secondary prevention of lower limb muscle cramps. Cochrane Database Syst Rev 2021; 5:CD008496. [PMID: 33998664 PMCID: PMC8127570 DOI: 10.1002/14651858.cd008496.pub3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND Lower limb muscle cramps are common and painful. They can limit exercise participation, and reduce quality of sleep, and quality of life. Many interventions are available for lower limb cramps; some are controversial or could cause harm, and often, people experience no benefit from the interventions used. This is an update of a Cochrane Review first published in 2012. We updated the review to incorporate new evidence. OBJECTIVES To assess the effects of non-drug, non-invasive therapies for lower limb muscle cramps. SEARCH METHODS In August 2018 and May 2020, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, the World Health Organization International Clinical Trials Registry Platform, ClinicalTrials.gov, and reference lists of included studies. We imposed no restrictions by language or publication date. SELECTION CRITERIA We included all randomised controlled trials (RCTs) of non-drug, non-invasive interventions tested over at least four weeks, for lower limb muscle cramps in any group of people, except pregnant women. The primary outcome was cramp frequency. Secondary outcomes were cramp pain severity, cramp duration, health-related quality of life, quality of sleep, participation in activities of daily living, proportion of participants reporting lower limb muscle cramps, and adverse events. DATA COLLECTION AND ANALYSIS Two review authors independently selected trials, assessed risk of bias, and cross-checked data extraction and analyses according to standard Cochrane procedures. MAIN RESULTS We included three trials, with 201 participants, all 50 years of age and older; none had neurological disease. All trials evaluated a form of stretching for lower limb muscle cramps. A combination of daily calf and hamstring stretching for six weeks may reduce the severity of night-time lower limb muscle cramps (measured on a 10 cm visual analogue scale (VAS) where 0 = no pain and 10 cm = worst pain imaginable) in people aged 55 years and older, compared to no intervention (mean difference (MD) -1.30, 95% confidence interval (CI) -1.74 to -0.86; 1 RCT, 80 participants; low-certainty evidence). The certainty of evidence was very low for cramp frequency (change in number of cramps per night from week zero to week six) comparing the stretching group and the no intervention group (MD -1.2, 95% CI -1.8 to -0.6; 80 participants; very low-certainty evidence). Calf stretching alone for 12 weeks may make little to no difference to the frequency of night-time lower limb muscle cramps in people aged 60 years and older (stretching group median number of cramps in the last four weeks (Md) 4, interquartile range (IQR) 8; N = 48; sham stretching group Md 3, IQR 7.63; N = 46) (U = 973.5, z = -0.995, P = 0.32, r = 0.10; 1 RCT, 94 participants; low-certainty evidence). This trial did not report cramp severity. The evidence is very uncertain about the effects of a combination of daily calf, quadriceps, and hamstring stretching on the frequency and severity of leg cramps in 50- to 60-year-old women with metabolic syndrome (N = 24). It was not possible to fully analyse the frequency data and the scale used to measure cramp severity is not validated. No study reported health-related quality of life, quality of sleep, or participation in activities of daily living. No participant in these three studies reported adverse events. The evidence for adverse events was of moderate certainty as the studies were too small to detect uncommon events. In two of the three studies, outcomes were at risk of recall bias, and tools used to measure outcomes were not validated. Due to limitations in study designs that led to risks of bias, and imprecise findings with wide CIs, we cannot be certain that findings of future studies will be similar to those presented in this review. AUTHORS' CONCLUSIONS A combination of daily calf and hamstring stretching for six weeks may reduce the severity of night-time lower limb muscle cramps in people aged 55 years and older, but the effect on cramp frequency is uncertain. Calf stretching alone compared to sham stretching for 12 weeks may make little or no difference to the frequency of night-time lower limb muscle cramps in people aged 60 years and older. The evidence is very uncertain about the effects of a combination of daily calf, quadriceps, and hamstring stretching on the frequency and severity of leg cramps in 50- to 60-year-old women with metabolic syndrome. Overall, use of unvalidated outcome measures and inconsistent diagnostic criteria make it difficult to compare the studies and apply findings to clinical practice. Given the prevalence and impact of lower limb muscle cramps, there is a pressing need to carefully evaluate many of the commonly recommended and emerging non-drug therapies in well-designed RCTs across all types of lower limb muscle cramps. A specific cramp outcome tool should be developed and validated for use in future research.
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Affiliation(s)
- Fiona Hawke
- School of Health Sciences, Faculty of Health and Medicine, The University of Newcastle, Ourimbah, Australia
| | - Sean G Sadler
- School of Health Sciences, Faculty of Health and Medicine, The University of Newcastle, Ourimbah, Australia
| | - Hans Dieter Katzberg
- Department of Neuromuscular Medicine, University of Toronto, Toronto General Hospital / UHN, Toronto, Canada
| | - Fereshteh Pourkazemi
- University of Sydney School of Health Sciences, Faculty of Medicine and Health, Sydney, Australia
| | - Vivienne Chuter
- School of Health Sciences, Faculty of Health and Medicine, The University of Newcastle, Ourimbah, Australia
| | - Joshua Burns
- University of Sydney School of Health Sciences, Faculty of Medicine and Health, Sydney, Australia
- The Children's Hospital at Westmead, Sydney, Australia
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Harmsen JF, Latella C, Mesquita R, Fasse A, Schumann M, Behringer M, Taylor J, Nosaka K. H-reflex and M-wave responses after voluntary and electrically evoked muscle cramping. Eur J Appl Physiol 2020; 121:659-672. [PMID: 33245422 DOI: 10.1007/s00421-020-04560-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 11/10/2020] [Indexed: 11/28/2022]
Abstract
PURPOSE Despite the widespread occurrence of muscle cramps, their underlying neurophysiological mechanisms remain unknown. To better understand the etiology of muscle cramps, this study investigated acute effects of muscle cramping induced by maximal voluntary isometric contractions (MVIC) and neuromuscular electrical stimulation (NMES) on the amplitude of Hoffmann reflexes (H-reflex) and compound muscle action potentials (M-wave). METHODS Healthy men (n = 14) and women (n = 3) participated in two identical sessions separated by 7 days. Calf muscle cramping was induced by performing MVIC of the plantar flexors in a prone position followed by 2.5-s NMES over the plantar flexors with increasing frequency and intensity. H-reflexes and M-waves evoked by tibial nerve stimulation in gastrocnemius medialis (GM) and soleus were recorded at baseline, and after MVIC-induced cramps and the NMES protocol. RESULTS Six participants cramped after MVIC, and H-reflex amplitude decreased in GM and soleus in Session 1 (- 33 ± 32%, - 34 ± 33%, p = 0.031) with a similar trend in Session 2 (5 cramped, p = 0.063), whereas the maximum M-wave was unchanged. After NMES, 11 (Session 1) and 9 (Session 2) participants cramped. H-reflex and M-wave recruitment curves shifted to the left in both sessions and muscles after NMES independent of cramping (p ≤ 0.001). CONCLUSION Changes in H-reflexes after a muscle cramp induced by MVIC and NMES were inconsistent. While MVIC-induced muscle cramps reduced H-reflex amplitude, muscle stretch to end cramping was a potential contributing factor. By contrast, NMES may potentiate H-reflexes and obscure cramp-related changes. Thus, the challenge for future studies is to separate the neural consequences of cramping from methodology-based effects.
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Affiliation(s)
- Jan-Frieder Harmsen
- Department of Molecular and Cellular Sports Medicine, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany.
- Department of Nutrition and Movement Sciences, School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands.
| | - Christopher Latella
- Center for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
- Neurophysiology Research Laboratory, Edith Cowan University, Joondalup, WA, Australia
| | - Ricardo Mesquita
- Center for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
| | | | - Moritz Schumann
- Department of Molecular and Cellular Sports Medicine, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany
| | - Michael Behringer
- Faculty of Sport Sciences, Goethe University Frankfurt, Frankfurt, Germany
| | - Janet Taylor
- Center for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
- Neurophysiology Research Laboratory, Edith Cowan University, Joondalup, WA, Australia
| | - Kazunori Nosaka
- Center for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
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Harmsen JF, Sistig A, Fasse A, Hackl M, Wegmann K, Behringer M. Neuromuscular Electrical Stimulation Reduces Leg Cramps in Patients With Lumbar Degenerative Disorders: A Randomized Placebo-Controlled Trial. Neuromodulation 2020; 24:1483-1492. [PMID: 33169444 PMCID: PMC9292613 DOI: 10.1111/ner.13315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 10/05/2020] [Accepted: 10/19/2020] [Indexed: 11/29/2022]
Abstract
Objectives Lumbar spinal stenosis (LSS) and lumbar disc herniation (LDH) are often accompanied by frequently occurring leg cramps severely affecting patients' life and sleep quality. Recent evidence suggests that neuromuscular electric stimulation (NMES) of cramp‐prone muscles may prevent cramps in lumbar disorders. Materials and Methods Thirty‐two men and women (63 ± 9 years) with LSS and/or LDH suffering from cramps were randomly allocated to four different groups. Unilateral stimulation of the gastrocnemius was applied twice a week over four weeks (3 × 6 × 5 sec stimulation trains at 30 Hz above the individual cramp threshold frequency [CTF]). Three groups received either 85%, 55%, or 25% of their maximum tolerated stimulation intensity, whereas one group only received pseudo‐stimulation. Results The number of reported leg cramps decreased in the 25% (25 ± 14 to 7 ± 4; p = 0.002), 55% (24 ± 10 to 10 ± 11; p = 0.014) and 85%NMES (23 ± 17 to 1 ± 1; p < 0.001) group, whereas it remained unchanged after pseudo‐stimulation (20 ± 32 to 19 ± 33; p > 0.999). In the 25% and 85%NMES group, this improvement was accompanied by an increased CTF (p < 0.001). Conclusion Regularly applied NMES of the calf muscles reduces leg cramps in patients with LSS/LDH even at low stimulation intensity.
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Affiliation(s)
- Jan-Frieder Harmsen
- Faculty of Sport Sciences, Goethe University Frankfurt, Frankfurt, Germany.,Department of Nutrition and Movement Sciences, School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Anna Sistig
- Faculty of Medicine, University Cologne, Cologne, Germany
| | | | - Michael Hackl
- Department of Orthopaedics and Trauma surgery, University Cologne, Cologne, Germany
| | - Kilian Wegmann
- Department of Orthopaedics and Trauma surgery, University Cologne, Cologne, Germany
| | - Michael Behringer
- Faculty of Sport Sciences, Goethe University Frankfurt, Frankfurt, Germany
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Akerman AP, Walker RJ, Schollum JBW, Putt TL, Wilson LC. Refinement of a protocol to induce reliable muscle cramps in the abductor hallucis. Physiol Meas 2020; 41:055003. [DOI: 10.1088/1361-6579/ab8855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Behringer M, Harmsen JF, Fasse A, Mester J. Effects of Neuromuscular Electrical Stimulation on the Frequency of Skeletal Muscle Cramps: A Prospective Controlled Clinical Trial. Neuromodulation 2017; 21:815-822. [PMID: 29164749 DOI: 10.1111/ner.12728] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 09/14/2017] [Accepted: 10/03/2017] [Indexed: 11/29/2022]
Abstract
OBJECTIVES We investigated if neuromuscular electrical stimulation (NMES) of calf muscles prevents spontaneous calf cramps. MATERIALS AND METHODS In 19 individuals affected by more than or equal to one calf cramp per week the gastrocnemius of the predominantly affected leg was stimulated twice a week (intervention leg, IL) over six weeks (3 × 6 stimulation trains at 30 Hz above the individual cramp threshold frequency). The other leg served as control (CL). The participants were advised to record all spontaneous muscle cramps from two weeks before the intervention until two weeks after the last NMES session. RESULTS The number of spontaneous calf cramps in the two weeks after the intervention was 78% lower (2.1 ± 6.8 cramps) in the stimulated (p < 0.001) and 63% lower (2.0 ± 6.9 cramps) in the unstimulated calves (p < 0.001), when compared to the two weeks prior to the intervention (IL: 9.6 ± 12.4 cramps; CL: 5.5 ± 12.7 cramps). Only in the IL, this improvement was accompanied by an increase in the cramp threshold frequency from 15.5 ± 8.5 Hz before the NMES intervention to 21.7 ± 12.4 Hz after the intervention. The severity of the remaining calf cramps tended to be lower in both legs after the intervention. CONCLUSIONS The applied stimulation protocol seems to provide an effective prevention strategy in individuals affected by regular calf cramps.
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Affiliation(s)
- Michael Behringer
- Institute of Sports Sciences, Goethe University Frankfurt, Frankfurt, Germany
| | - Jan-Frieder Harmsen
- German Research Center for Elite Sports-momentum, German Sport University Cologne, Cologne, Germany
| | | | - Joachim Mester
- German Research Center for Elite Sports-momentum, German Sport University Cologne, Cologne, Germany
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Behringer M, Nowak S, Leyendecker J, Mester J. Effects of TRPV1 and TRPA1 activators on the cramp threshold frequency: a randomized, double-blind placebo-controlled trial. Eur J Appl Physiol 2017; 117:1641-1647. [PMID: 28573374 DOI: 10.1007/s00421-017-3653-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 05/27/2017] [Indexed: 12/19/2022]
Abstract
PURPOSE Previous data indicate that a strong sensory input from orally administered TRPV1 and TRPA1 activators alleviates muscle cramps in foot muscles by reducing the α-motor neuron hyperexcitability. We investigated if TRP activators increase the cramp threshold frequency of the medial gastrocnemius. METHODS We randomly assigned 22 healthy male participants to an intervention (IG) and a control group (CG). While participants of the IG ingested a mixture of TRPV1 and TRPA1 activators, the CG received a placebo. We tested the cramp threshold frequency (CTF), the cramp intensity (EMG activity), and the perceived pain of electrically induced muscle cramps before (pre), and 15 min, 4, 8, and 24 h after either treatment. We further measured the maximal isometric force of knee extensors at pre, 4, and 24 h to assess potential side-effects on the force output. RESULTS When we included all measurement time points, no group-by-time interaction was observed for the CTF. However, when only pre and 15 min values were incorporated, a significant interaction, with a slightly greater CTF increase in IG (3.1 ± 1.5) compared to the CG (2.0 ± 1.5), was observed. No significant group by time interaction was found for the cramp intensity, the perceived pain, and the maximal isometric force. CONCLUSION Our data indicate that orally administered TRPV1 and TRPA1 activators exert a small short-term effect on the CTF, but not on the other parameters tested. Future studies need to investigate whether such small CTF increments are sufficient to prevent exercise-associated muscle cramps.
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Affiliation(s)
- Michael Behringer
- German Research Center of Elite Sport - momentum, German Sport University Cologne, Cologne, Germany. .,Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Cologne, Germany. .,Institute of Cardiology and Sports Medicine, German Sport University Cologne, Cologne, Germany.
| | - Stephanie Nowak
- German Research Center of Elite Sport - momentum, German Sport University Cologne, Cologne, Germany
| | - Jannik Leyendecker
- German Research Center of Elite Sport - momentum, German Sport University Cologne, Cologne, Germany
| | - Joachim Mester
- German Research Center of Elite Sport - momentum, German Sport University Cologne, Cologne, Germany
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Behringer M, Spieth V, Montag JCK, Willwacher S, McCourt ML, Mester J. Cramp Training Induces a Long-Lasting Increase of the Cramp Threshold Frequency in Healthy Subjects. Neuromodulation 2016; 21:809-814. [PMID: 27641444 DOI: 10.1111/ner.12525] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 08/03/2016] [Accepted: 08/14/2016] [Indexed: 11/27/2022]
Abstract
OBJECTIVE A low cramp threshold frequency (CTF) is associated with an increased cramp susceptibility. Recent data indicate that the CTF can be substantially increased by a cramp training consisting of electrically induced muscle cramps (EIMCs). This study investigated if four cramp training sessions induce sustained effects on the CTF. METHODS In ten healthy male subjects, EIMCs were induced in the gastrocnemius medialis of one leg (intervention leg, IL) twice a week, while the opposite leg served as control leg (CL). The stimulation protocol consisted of three sets of six bipolar rectangular wave pulsed currents (5 sec on, 10 sec off) at 30 Hz above the individual CTF. RESULTS After four cramp training sessions (2 weeks) the CTF differed (p < 0.001) from pre-values in the IL (pre: 19.2 ± 1.4 Hz post 29.8 ± 8.0 Hz) but not in the CL (pre: 18.2 ± 1.5 Hz post 19.6 ± 2.8 Hz; p > 0.05). Thereafter, the CTF remained elevated in the IL for 22 days (22 days post: 22.2 ± 3.2 Hz; p < 0.05) when compared to pre and was significantly (p < 0.05) higher than that of the CL 5, 10, and 14 days after the intervention. CONCLUSION The applied cramp training induced a long-term CTF increase of 14 days.
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Affiliation(s)
- Michael Behringer
- Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.,German Research Center of Elite Sports (momentum), German Sport University Cologne, Cologne, Germany
| | - Volker Spieth
- Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany
| | - Johannes Caspar Konrad Montag
- Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.,German Research Center of Elite Sports (momentum), German Sport University Cologne, Cologne, Germany
| | - Steffen Willwacher
- Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Cologne, Germany
| | - Molly Leigh McCourt
- Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany
| | - Joachim Mester
- Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.,German Research Center of Elite Sports (momentum), German Sport University Cologne, Cologne, Germany
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Nelson NL, Churilla JR. A narrative review of exercise-associated muscle cramps: Factors that contribute to neuromuscular fatigue and management implications. Muscle Nerve 2016; 54:177-85. [DOI: 10.1002/mus.25176] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/03/2016] [Indexed: 11/09/2022]
Affiliation(s)
- Nicole L. Nelson
- Clinical and Applied Movement Sciences, Brooks College of Health, University of North Florida; 1 UNF Drive Jacksonville Florida 32224-2673 USA
| | - James R. Churilla
- Clinical and Applied Movement Sciences, Brooks College of Health, University of North Florida; 1 UNF Drive Jacksonville Florida 32224-2673 USA
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Behringer M, Link TW, Montag JCK, McCourt ML, Mester J. Are Electrically Induced Muscle Cramps Able to Increase the Cramp Threshold Frequency, When Induced Once a Week? Orthop Rev (Pavia) 2015; 7:6028. [PMID: 26605029 PMCID: PMC4592932 DOI: 10.4081/or.2015.6028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 06/28/2015] [Indexed: 11/23/2022] Open
Abstract
The cramp threshold frequency (CTF) is known to be positively correlated with the individual cramp susceptibility. Here we assessed CTF changes after two bouts of electrically induced muscle cramps (EIMCs). The EIMCs (6×5 sec) were unilaterally induced twice (separated by one week) in the gastrocnemius of an intervention group (n=8), while 5 participants served as control. The CTF increased from 25.1±4.6 Hz at baseline to 31.4±9.0 Hz and 31.7±8.5 Hz 24 h after bout 1 and 2 (P<0.05). Thereafter, the CTF declined following both bouts to reach values of 28.0±6.7 Hz and 29.1±7.7 Hz after 72 h after bout 1 and 2. Creatine kinase (CK) activity and perceived discomfort during cramps was lower after bout 2 (P<0.05). CTF, CK, and discomfort did not change in CG. That is, a single bout of EIMCs induces a 24 h CTF increment and a second bout sustains this effect, while perceived discomfort and muscle damage decreases. This short term effect may help athletes to reduce the cramp susceptibility for an important match.
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Affiliation(s)
- Michael Behringer
- Institute for Training Science and Sport Informatics, German Sport University of Cologne , Germany
| | - Tobias Walter Link
- Institute for Training Science and Sport Informatics, German Sport University of Cologne , Germany
| | | | - Molly Leigh McCourt
- Institute for Training Science and Sport Informatics, German Sport University of Cologne , Germany
| | - Joachim Mester
- Institute for Training Science and Sport Informatics, German Sport University of Cologne , Germany
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Electrically induced muscle cramps induce hypertrophy of calf muscles in healthy adults. JOURNAL OF MUSCULOSKELETAL & NEURONAL INTERACTIONS 2015; 15:227-36. [PMID: 26032216 PMCID: PMC5133727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVES Skeletal muscles usually cramp at short lengths, where the tension that can be exerted by muscle fibers is low. Since high tension is an important anabolic stimulus, it is questionable if cramps can induce hypertrophy and strength gains. In the present study we investigated if electrically induced cramps (EIMCs) can elicit these adaptations. METHODS 15 healthy male adults were randomly assigned to an intervention (IG; n=10) and a control group (CG; n=5). The cramp protocol (CP) applied twice a week to one leg of the IG, consisted of 3x6 EIMCs, of 5 s each. Calf muscles of the opposite leg were stimulated equally, but were hindered from cramping by fixating the ankle at 0° plantar flexion (nCP). RESULTS After six weeks, the cross sectional area of the triceps surae was similarly increased in both the CP (+9.0±3.4%) and the nCP (+6.8±3.7%). By contrast, force of maximal voluntary contractions, measured at 0° and 30° plantar flexion, increased significantly only in nCP (0°: +8.5±8.8%; 30°: 11.7±13.7%). CONCLUSION The present data indicate that muscle cramps can induce hypertrophy in calf muscles, though lacking high tension as an important anabolic stimulus.
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