The End of the Formal Rehabilitation Is Not the End of Rehabilitation: Knee Function Deficits Remain After Anterior Cruciate Ligament Reconstruction.

OBJECTIVE: To rate athletes' functional ability and return to sport (RTS) success at the end of their individual, formal, medically prescribed rehabilitation after anterior anterior cruciate ligament (ACL) reconstruction. METHODS: In our prospective multicenter cohort study, 88 (42 females) adults aged 18-35 years after acute unilateral ACL rupture and subsequent hamstring grafting were included. All patients were prospectively monitored during their rehabilitation and RTS process until the end of their formal rehabilitation and RTS release. As outcome measures, functional hop and jump tests (front hop, balance hops, and drop jump screening test) and self-report outcomes (Knee Injury and Osteoarthritis Outcome Score, ACL-RTS after injury) were assessed. Literature-based cut-off values were selected to rate each performance as fulfilled or not. RESULTS: At 7.5 months (SD 2.3 months) after surgery, the percentage of participants meeting the functional thresholds ranged from 4% (Knee Injury and Osteoarthritis Outcome Score SPORT) and over 44% (ACL-RTS after injury sum score) to 59% (Knee Injury and Osteoarthritis Outcome Score activities of all daily living) in the self-report and from 29% (Balance side hop) to 69% (normalized knee separation distance) in performance testing. Only 4% fulfilled all the cut-offs, while 45% returned to the same type and level of sport. Participants who successfully returned to their previous sport (type and level) were more likely to be "over-cut-off-performers." CONCLUSIONS: The low share of the athletes who fulfilled the functional RTS criteria highlights the importance of continuing the rehabilitation measures after the formal completion to assess the need for and success of, inter alia, secondary-preventive therapies.

Comparative Effectiveness of Upper Limb Exercise Interventions in Individuals With Stroke: A Network Meta-Analysis.

BACKGROUND: Although numerous effective exercise interventions can treat upper limb motor impairments after stroke, it remains unknown as to which are the most effective. The objective of the present study was to investigate the comparative effectiveness of various exercise interventions of the upper limb for individuals with an acute or subacute stroke. METHODS: For this systematic review with network meta-analysis, we searched PubMed/MEDLINE, Cochrane Library CENTRAL and Web of Science from database inception to September 2021 for randomized controlled trials examining individuals within 6 months of stroke onset, active upper limb exercise interventions, and any kind of control intervention. The primary outcome was upper limb motor function, secondary outcomes were activities of daily living and social participation, both assessed at post-intervention and follow-up. Nonspecific/multimodal active upper limb therapy was the standard comparator. Standardized mean differences, that is, Hedge's g, were the effect size estimators. We calculated Frequentist-based network meta-analysis for the comparative effectiveness calculations using the R package netmeta. Main analyses were network plotting to display the geometry of the network and P-scores to summarize the intervention hierarchy. Results were derived from direct within-study and indirect between-study evidence comparisons. The Cochrane risk-of-bias tool II assessed all risk of bias domains. RESULTS: This review involved 145 randomized controlled trial on 6432 participants and 45 different treatment categories. The network meta-analysis analyzed 119 randomized controlled trials on 5553 participants and 41 different treatment categories. Electrical stimulation combined with task-specific training (standardized mean difference, 1.03 [95% CI, 0.51-1.55]; P<0.0001, P-score=0.11), high-volume constraint-induced movement therapy (0.86 [0.4-1.32]; P=0.0003, P-score=0.18), and strength training (0.65 [0.17-1.13]; P=0.01, P-score=0.28) were the most effective interventions (each k=107). CONCLUSIONS: Electrical stimulation combined with task-specific training (low evidence), high-volume constraint-induced movement therapy (moderate evidence), and strength training (low evidence) were the most effective interventions in improving upper limb motor function in individuals with a stroke. As the results were sensitive against a high risk of bias, likewise, these interventions should receive more attention in research and practice. Due to the heterogeneous use, electrical stimulation in combination with task-specific training should be further investigated in well-designed studies alongside other successful interventions (eg, constraint-induced movement therapy). REGISTRATION: URL: https://www.crd.york.ac.uk/prospero/; Unique identifier: CRD42021284064.

Resistance training volume does not influence lean mass preservation during energy restriction in trained males.

This study investigated the effects of a relatively high- versus moderate-volume resistance training program on changes in lean mass during caloric restriction. Thirty-eight resistance-trained males were randomized to perform either a high-volume (HVG; 5 sets/exercise) or a moderate-volume (MVG; 3 sets/exercise) resistance training program. Both groups were supervised during lower body training. Participants consumed 30 kcal/kg for 6 weeks after 1 week of weight maintenance (45 kcal/kg), with protein intake fixed at 2.8 g/kg fat-free mass. Muscle thickness of the m. rectus femoris, body composition, contractile properties, stiffness, mood, and sleep status were assessed at pre-, mid-, and post-study. No significant group × time interaction was observed for muscle thickness of the m. rectus femoris at 50% (∆ [post-pre] 0.36 ± 0.93 mm vs. ∆ -0.01 ± 1.59 mm; p = 0.226) and 75% length (∆ -0.32 ± 1.12 mm vs. ∆ 0.08 ± 1.14 mm; p = 0.151), contractility, sleep, and mood in the HVG and MVG, respectively. Body mass (HVG: ∆ -1.69 ± 1.12 kg vs. MVG: ∆ -1.76 ± 1.76 kg) and lean mass (∆ -0.51 ± 2.30 kg vs. ∆ -0.92 ± 1.59 kg) decreased significantly in both groups (p = 0.022), with no between-group difference detected (p = 0.966). High-volume resistance training appears to have neither an advantage nor disadvantage over moderate-volume resistance training in terms of maintaining lean mass or muscle thickness. Given that both groups increased volume load and maintained muscle contractility, sleep quality, and mood, either moderate or higher training volumes conceivably can be employed by resistance-trained individuals to preserve muscle during periods of moderate caloric restriction.

Effects of muscle fatigue on exercise-induced hamstring muscle damage: a three-armed randomized controlled trial.

PURPOSE: Hamstring injuries in soccer reportedly increase towards the end of the matches' halves as well as with increased match frequency in combination with short rest periods, possibly due to acute or residual fatigue. Therefore, this study aimed to investigate the effects of acute and residual muscle fatigue on exercise-induced hamstring muscle damage. METHODS: A three-armed randomized-controlled trial, including 24 resistance-trained males, was performed allocating subjects to either a training group with acute muscle fatigue + eccentric exercise (AF/ECC); residual muscle fatigue + eccentric exercise (RF/ECC) or a control group with only eccentric exercise (ECC). Muscle stiffness, thickness, contractility, peak torque, range of motion, pain perception, and creatine kinase were assessed as muscle damage markers pre, post, 1 h post, and on the consecutive three days. RESULTS: Significant group × time interactions were revealed for muscle thickness (p = 0.02) and muscle contractility parameters radial displacement (Dm) and contraction velocity (Vc) (both p = 0.01), with larger changes in the ECC group (partial η2 = 0.4). Peak torque dropped by an average of 22% in all groups; stiffness only changed in the RF/ECC group (p = 0.04). Muscle work during the damage protocol was lower for AF/ECC than for ECC and RF/ECC (p = 0.005). CONCLUSION: Hamstring muscle damage was comparable between the three groups. However, the AF/ECC group resulted in the same amount of muscle damage while accumulating significantly less muscle work during the protocol of the damage exercise. TRIAL REGISTRATION: This study was preregistered in the international trial registration platform (WHO; registration number: DRKS00025243).

Quadriceps and hamstring anterior cruciate ligament reconstruction differ only marginally in function after the rehabilitation: a propensity score-matched case-control study.

PURPOSE: To determine potential quadriceps versus hamstring tendon autograft differences in neuromuscular function and return to sport (RTS)-success in participants after an anterior cruciate ligament (ACL) reconstruction. METHODS: Case-control study on 25 participants operated on with an arthroscopically assisted, anatomic ipsilateral quadriceps femoris tendon graft and two control groups of 25 participants each, operated on with a semitendinosus tendon or semitendinosus-gracilis (hamstring) tendon graft ACL reconstruction. Participants of the two control groups were propensity score matched to the case group based on sex, age, Tegner activity scale and either the total volume of rehabilitation since reconstruction (n = 25) or the time since reconstruction (n = 25). At the end of the rehabilitation (averagely 8 months post-reconstruction), self-reported knee function (KOOS sum scores), fear of loading the reconstructed knee during a sporting activity (RSI-ACL questionnaire), and fear of movement (Tampa scale of kinesiophobia) were followed by hop and jump tests. Front hops for distance (jumping distance as the outcome) were followed by Drop jumps (normalised knee joint separation distance), and concluded by qualitative ratings of the Balanced front and side hops. Between-group comparisons were undertaken using 95% confidence intervals comparisons, effect sizes were calculated. RESULTS: The quadriceps case group (always compared with the rehabilitation-matched hamstring graft controls first and versus time-matched hamstring graft controls second) had non-significant and only marginal higher self-reported issues during sporting activities: Cohen's d = 0.42, d = 0.44, lower confidence for RTS (d = - 0.30, d = - 0.16), and less kinesiophobia (d = - 0.25, d = 0.32). Small and once more non-significant effect sizes point towards lower values in the quadriceps graft groups in the Front hop for distance limb symmetry values in comparison to the two hamstring control groups (d = - 0.24, d = - 0.35). The normalised knee joint separation distance were non-significantly and small effect sized higher in the quadriceps than in the hamstring groups (d = 0.31, d = 0.28). CONCLUSION: Only non-significant and marginal between-graft differences in the functional outcomes at the end of the rehabilitation occurred. The selection of either a hamstring or a quadriceps graft type cannot be recommended based on the results. The decision must be undertaken individually. LEVEL OF EVIDENCE: III.

The course of knee extensor strength after total knee arthroplasty: a systematic review with meta-analysis and -regression.

PURPOSE: Muscular strength loss and atrophy are postoperative complications. This systematic review with meta-analysis investigated the course of on knee extensor mass and strength from pre-surgery over total knee arthroplasty to rehabilitation and recovery. METHODS: A systematic literature search was conducted in PubMed (Medline), Cochrane Library (CINAHL, Embase) and Web of Science (until 29th of June 2022). Main inclusion criteria were ≥ 1 preoperative and ≥ 1 measurement ≥ 3-months post-operation and ≥ 1 objective assessment of quadriceps strength, muscle mass or neuromuscular activity, measured at both legs. Studies were excluded if they met the following criteria: further impairment of treated extremity or of the contralateral extremity; further muscle affecting disease, or muscle- or rehabilitation-specific intervention. The Robins-I tool for non-randomized studies, and the Cochrane Rob 2 tool for randomized controlled studies were used for risk of bias rating. Pre-surgery, 3 months, 6 months and 1 year after surgery data were pooled using random effects meta-analyses (standardized mean differences, SMD, Hedge's g) in contrast to the pre-injury values. RESULTS: 1417 studies were screened, 21 studies on 647 participants were included. Thereof, 13 were non-randomized controlled trails (moderate overall risk of bias in most studies) and 7 were randomized controlled trials (high risk of bias in at least one domain in most studies). Three (k = 12 studies; SMD = - 0.21 [95% confidence interval = - 0.36 to - 0.05], I2 = 4.75%) and six (k = 9; SMD = - 0.10 [- 0.28 to - 0.08]; I2 = 0%) months after total knee arthroplasty, a deterioration in the strength of the operated leg compared with the strength of the non-operated leg was observed. One year after surgery, the operated leg was stronger in all studies compared to the preoperative values. However, this increase in strength was not significant compared to the non-operated leg (k = 6, SMD = 0.18 [- 0.18 to 0.54], I2 = 77.56%). CONCLUSION: We found moderate certainty evidence that deficits in muscle strength of the knee extensors persist and progress until 3 months post-total knee arthroplasty in patients with end-stage knee osteoarthritis. Very low certainty evidence exists that preoperatively existing imbalance of muscle strength and mass in favor of the leg not undergoing surgery is not recovered within 1 year after surgery.

Neuromuscular Electrical Stimulation Training vs. Conventional Strength Training: A Systematic Review and Meta-Analysis of the Effect on Strength Development.

ABSTRACT: Happ, KA, and Behringer, M. Neuromuscular electrical stimulation Training vs. conventional strength training: a systematic review and meta-analysis of the effect on strength development. J Strength Cond Res 36(12): 3527-3540, 2022-A systematic review of the current state of literature and a meta-analysis were conducted to compare the strength development between neuromuscular electrical stimulation (NMES) and conventional strength training when training volume is matched. Searches of PubMed and several other databases were conducted for studies that met the following primary inclusion criteria: randomized studies of >20 days duration with a sample size of >4 subjects in each group ("voluntary contraction" [VC] and "electrically stimulated" [ES]) conducted with percutaneous stimulation only in healthy individuals at equal training volume. Finally, a total of 19 studies were included in the analysis. When comparing strength gains between groups (ES-VC), no favorable effect toward a training method could be observed (0.023 hg [95% CI: -0.198 to 0.246, p = 0.836]). Subgroup analyses were performed based on the application type (NMES evoked and NMES onto voluntary contractions) and stimulation frequency. Both analyses revealed no favorable effect and significant difference of groups (significance level set at 0.05). A meta-regression evaluated the relationship between stimulation frequency and effect size difference. The regression showed a tendency of higher stimulation frequencies being associated with higher study effect size differences (predicted effect size = -0.599 + 0.008 (Hz) ( p = 0.176)). The findings indicate that training with NMES results in virtually identical strength gains compared with conventional strength training when training volume is matched. If training with NMES is preferred, the stimulation frequency type (regular or Burst Mode Alternating Current) can be chosen according to preference without loss of effectiveness.

Effects of Maximal Eccentric Exercise on Deep Fascia Stiffness of the Knee Flexors: A Pilot Study using Shear-Wave Elastography.

The deep fascia is intimately linked to skeletal muscle and may be involved in delayed onset muscle soreness (DOMS). The present study therefore explored the effect of eccentric exercise on fascia stiffness and its relation with DOMS. Healthy active male adults (n = 19, 27 ± 4 years) performed 6 x 10 maximal eccentric knee flexions using an isokinetic dynamometer. Before (baseline) as well as immediately (T0), 1 hour (T1), and each day up to 72 hours (T24 to T72) afterwards, shear wave elastography was used to measure the mechanical stiffness of the biceps femoris muscle and the overlying fascia. As a surrogate of DOMS, pain upon palpation was captured by means of a 100mm visual analogue scale. While muscle stiffness remained unchanged (p > 0.05), deep fascia stiffness increased from baseline to T24 (median: 18 kPa to 21.12 kPa, p = 0.017) and T72 (median: 18 kPa to 21.3 kPa, p = 0.001) post-exercise. Linear regression showed an association of stiffness changes at T24 and pressure pain at T72 (r2 = 0.22, p < 0.05). Maximal eccentric exercise leads to a stiffening of the fascia, which, in turn, is related to the magnitude of future DOMS. Upcoming research should therefore gauge the effectiveness of interventions modifying the mechanical properties of the connective tissue in order to accelerate recovery.

H-reflex and M-wave responses after voluntary and electrically evoked muscle cramping.

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.

Neuromuscular Electrical Stimulation Reduces Leg Cramps in Patients With Lumbar Degenerative Disorders: A Randomized Placebo-Controlled Trial.

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.

Is "Delayed Onset Muscle Soreness" a False Friend? The Potential Implication of the Fascial Connective Tissue in Post-Exercise Discomfort.

Strenuous and unaccustomed exercise frequently lead to what has been coined "delayed onset muscle soreness" (DOMS). As implied by this term, it has been proposed that the associated pain and stiffness stem from micro-lesions, inflammation, or metabolite accumulation within the skeletal muscle. However, recent research points towards a strong involvement of the connective tissue. First, according to anatomical studies, the deep fascia displays an intimate structural relationship with the underlying skeletal muscle and may therefore be damaged during excessive loading. Second, histological and experimental studies suggest a rich supply of algogenic nociceptors whose stimulation evokes stronger pain responses than muscle irritation. Taken together, the findings support the hypothesis that DOMS originates in the muscle-associated connective tissue rather than in the muscle itself. Sports and fitness professionals designing exercise programs should hence consider fascia-oriented methods and techniques (e.g., foam rolling, collagen supplementation) when aiming to treat or prevent DOMS.

Tensiomyography parameters and serum biomarkers after eccentric exercise of the elbow flexors.

PURPOSE: The tensiomyography (TMG) technique is increasingly used to determine muscle contractile properties in exercise and injury management. The present study investigated the informative value of TMG parameters in correlation with commonly used (creatine kinase, CK; myoglobin, Mb) and novel candidate biomarkers of muscle damage (heart-type fatty acid-binding protein, h-FABP; high-mobility group box 1, HMGB1). METHODS: Ten untrained men performed 6 × 10 eccentric contractions of the elbow flexors at 110% of the concentric one repetition maximum. CK, Mb, h-FABP, HMGB1, arm circumference, pain and TMG data, including maximal displacement (Dm) and temporal outcomes as the contraction time (Tc), sustained time (Ts), delay time (Td), and relaxation time (Tr), were assessed pre-exercise, post-exercise, 20 min, 2 h and on the consecutive 3 days post-exercise. RESULTS: CK and h-FABP significantly increased beginning at 24 h, Mb already increased at 2 h (p < 0.05). HMGB1 was only increased immediately post-exercise (p = 0.02). Tc and Td remained unchanged, whereas Ts and Tr were significantly slower beginning at 24 h (p < 0.05). Dm was decreased within the first 24 h and after 72 h (p < 0.01). The % change from pre-exercise correlated for Dm with CK, Mb, and h-FABP the highest at 48 h (r = - 0.95, - 0.87 and - 0.79; p < 0.01) and for h-FABP with CK and Mb the highest at 24 h (r = 0.96 and 0.94, for all p < 0.001). CONCLUSION: This study supports the correlation of TMG parameters with muscle damage markers after eccentric exercise. Therefore, TMG could represent a non-invasive and cost effective alternative to quantify the degree of muscle damage after exercise interventions.

Exercise alarms the immune system: A HMGB1 perspective.

The "danger" model of immunology states that the immune system detects and responds to danger by releasing endogenous molecules called alarmins. Strenuous exercise perturbs physiological homeostasis, increasing circulating alarmins to drive the inflammatory response. We describe a working concept of exercise-induced High Mobility Group Box (HMGB)1, a prototypical alarmin, in modulating immune responses and adaptations.

Anatomical versus functional motor points of selected upper body muscles.

INTRODUCTION: In this study we aimed to identify nerve entry points (NEPs) of superficial skeletal muscles obtained by dissection of 20 human cadavers and compared them with motor points (MP) obtained previously by electrical stimulation. METHODS: The biceps brachii (BB), trapezius (TZ), latissimus dorsi (LD), pectoralis major (Pmaj), and pectoralis minor (Pmin) muscles were dissected from human cadavers. NEP data (mean ± standard deviation) from each muscle were calculated. F-tests with Bonferroni corrections were used to compare NEPs and MPs. RESULTS: The number of NEPs was 2 in BB, 1 in Pmin, 4 in TZ, and 3 in LD, whereas the total number in Pmaj varied from 3 to 5. NEPs and MPs were statistically equal only in Pmin and in the descending part of TZ. DISCUSSION: The findings show crucial differences between NEPs and MPs, possibly impacting the effectiveness of several medical treatment strategies. Muscle Nerve 57: 460-465, 2018.

Wear Kinetics of Highly Cross-Linked and Conventional Polyethylene Are Similar at Medium-term Follow-Up After Primary Total Hip Arthroplasty.

BACKGROUND: Wear debris is a major factor in aseptic loosening of total hip arthroplasty. Ultra high molecular weight polyethylene inlays are known for significant wear, and the following generation, highly cross-linked polyethylene (HCLPE), has shown promising in vitro and short-term in vivo results. This study aimed to investigate wear debris of HCLPE liners with ceramic heads after 9 years to reveal the in vivo wear kinetics of this common bearing combination. METHODS: Fifty-seven patients (72 hips; 46.5 ± 15.5 years; range 16-76 years) who underwent hip arthroplasty with an HCLPE liner (28- or 32-mm Biolox forte ceramic head) were followed up (mean 9.1 ± 2.4 years; range 3.9-13.8 years). Conventional anteroposterior X-rays were analyzed using Hip Analysis Suite software. RESULTS: Volumetric wear had a mean of 38.67 ± 22.09 mm3/year, 333.08 ± 183.93 mm3 overall, and linear wear was 0.063 ± 0.03 mm/year and 0.546 ± 0.27 mm overall. Male patients had a significantly higher wear rate (46.42 ± 27.68 mm3/year) and total wear (400.71 ± 235.21 mm3). Larger femoral heads had a significantly higher wear rate (43.10 ± 23.93 mm3/year) and total wear (364.23 ± 203.68 mm3). Regression analysis showed a significant cubic relationship (R2 = 0.307) with increasing yearly wear after approximately 108 months postoperatively. CONCLUSIONS: HCLPE liners show significant in vivo wear after 9 years. While the total wear compared to ultra high molecular weight polyethylene liners was decreased, the wear kinetics show a comparable course. The increase in wear rate after only 108 months postoperatively is especially alarming. Longer term follow-up is needed to distinguish the long-term superiority of HCLPE liners in polyethylene-ceramic paired hip arthroplasty.

Effects of Neuromuscular Electrical Stimulation on the Frequency of Skeletal Muscle Cramps: A Prospective Controlled Clinical Trial.

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.

Cramp Training Induces a Long-Lasting Increase of the Cramp Threshold Frequency in Healthy Subjects.

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.

Effects of TRPV1 and TRPA1 activators on the cramp threshold frequency: a randomized, double-blind placebo-controlled trial.

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.

Low-Intensity Sprint Training With Blood Flow Restriction Improves 100-m Dash.

Behringer, M, Behlau, D, Montag, JCK, McCourt, ML, and Mester, J. Low-intensity sprint training with blood flow restriction improves 100-m dash. J Strength Cond Res 31(9): 2462-2472, 2017-We investigated the effects of practical blood flow restriction (pBFR) of leg muscles during sprint training on the 100-m dash time in well-trained sport students. Participants performed 6 × 100-m sprints at 60-70% of their maximal 100-m sprinting speed twice a week for 6 weeks, either with (intervention group [IG]; n = 12) or without pBFR (control group [CG]; n = 12). The 100-m dash time significantly decreased more in the IG (-0.38 ± 0.24 seconds) than in the CG (-0.16 ± 0.17 seconds). The muscle thickness of the rectus femoris increased only in the IG, whereas no group-by-time interactions were found for the muscle thickness of the biceps femoris and the biceps brachii. The maximal isometric force, measured using a leg press, did not change in either group. However, the rate of force development improved in the IG. Growth hormone, testosterone, insulin-like growth factor 1, and cortisol concentrations did not significantly differ between both groups at any measurement time point (pre, 1 minute, 20 minutes, 120 minutes, and 24 hours after the 6 all-out sprints of the first training session). The muscle damage marker h-FABP increased significantly more in the CG than in the IG. The pBFR improved the 100-m dash time significantly more than low-intensity sprint interval training alone. Other noted benefits of training with pBFR were a decreased level of muscle damage, a greater increase of the rectus femoris muscle thickness, and a higher rate of force development. However, the tested hormones were unable to explain the additional beneficial effects.