Efficacy, feasibility and tolerability of ketogenic diet for the treatment of poor response to bariatric surgery.

PURPOSE: Poor response to bariatric surgery, namely insufficient weight loss (IWL) or weight regain (WR), is a critical issue in the treatment of obesity. The purpose of our study was to assess the efficacy, feasibility, and tolerability of very low-calorie ketogenic diet (VLCKD) for the management of this condition. METHODS: A real-life prospective study was conducted on twenty-two patients who experienced poor response after bariatric surgery and followed a structured VLCKD. Anthropometric parameters, body composition, muscular strength, biochemical analyses, and nutritional behavior questionnaires were evaluated. RESULTS: A significant weight loss (mean 14.1 ± 4.8%), mostly due to fat mass, was observed during VLCKD with the preservation of muscular strength. The weight loss obtained allowed patients with IWL to reach a body weight significantly lower than that obtained at the post-bariatric surgery nadir and to report the body weight of patients with WR at the nadir observed after surgery. The significantly beneficial changes in nutritional behaviors and metabolic profiles were observed without variations in kidney and liver function, vitamins, and iron status. The nutritional regimen was well tolerated, and no significant side effects were detected. CONCLUSION: Our data demonstrate the efficacy, feasibility, and tolerability of VLCKD in patients with poor response after bariatric surgery.

Short-term efficacy of high intensity group and individual education in patients with type 2 diabetes: a randomized single-center trial.

PURPOSE: The aim of this randomized study was to examine the efficacy of two high intensity educational programs: the conversation maps-based (CM™) education and the individual education (IE), compared to usual care (UC) in a cohort of type 2 diabetic (T2DM) patients. METHODS: Ninety T2DM outpatients (30 per group) were randomized and 79 finished the study and were analyzed. The CM™ and IE groups received four educational sessions at 0, 4, 8 and 12 weeks, while the UC group received two brief individual sessions at 0 and 12 weeks. We evaluated glycemic control (HbA1c), diabetes treatment, body mass index (BMI) and carried out a questionnaire survey at three time points (before intervention, at 12 and at 32 weeks) to assess patients' satisfaction, attitudes toward diabetes and dietary knowledge. RESULTS: All the three groups showed a significant and comparable reduction of both HbA1c and BMI. Diabetes therapy needed to be reinforced in a higher percentage of cases (39.3%) among UC patients compared to the IE (14.8%; p = 0.04) and the CM™ (8.3%; p = 0.01) groups. At 32 weeks Diabetes Treatment Satisfaction (DTSQ Q1 + Q4-8) significantly improved in the CM™ group (25.8 ± 4.5 vs. 22.4 ± 6.0; p < 0.01) and attitudes toward diabetes (ATT19) significantly improved in the IE group (58.0 ± 4.7 vs. 55.3 ± 5.1; p = 0.02). CONCLUSIONS: Our trial provides preliminary data regarding the efficacy of structured group and individual education on achieving better glyco-metabolic control without drug therapy reinforcement and with positive effects on patients' attitude and treatment satisfaction.

Influence of early-life and parental factors on childhood overweight and obesity.

PURPOSE: We recently reported that a high BMI and high waist circumference prevalence is present in Sicilian children and that the male gender is associated with a significant risk of obesity. Early-life and parent-related risk factors were investigated 1521 Sicilian children (752 females and 769 males, aged 9.0-14.0 years) to identify biological and environmental factors that can contribute to obesity onset. METHODS: Anthropometric measurements of children, their urban vs rural area provenience, birth weight and neonatal feeding were collected. In addition, the BMI and educational level of their parents and the perception of their child weight status were investigated. RESULTS: In the study cohort, the prevalence of overweight and obesity was 27.2 and 14.1 %, respectively, significantly (p < 0.05) higher in males than in females. Breastfeeding emerged as a protective factor (OR 0.64; p < 0.0005), while risk factors for developing childhood obesity were a birth weight ≥4.0 kg (OR 1.83; p < 0.05), an overweight or obese mother (OR 2.33; p < 0.0001) or father (OR 1.68; p < 0.0001) and a mother with a low/medium education level (OR 1.72; p < 0.005). CONCLUSION: Understanding risk factors for pediatric obesity is a prerequisite to identify children at highly risk of being obese and to predispose early intervention strategies.

The SH2B1 obesity locus and abnormal glucose homeostasis: lack of evidence for association from a meta-analysis in individuals of European ancestry.

BACKGROUND/AIMS: The development of type 2 diabetes (T2D) is influenced both by environmental and by genetic determinants. Obesity is an important risk factor for T2D, mostly mediated by obesity-related insulin resistance. Obesity and insulin resistance are also modulated by the genetic milieu; thus, genes affecting risk of obesity and insulin resistance might also modulate risk of T2D. Recently, 32 loci have been associated with body mass index (BMI) by genome-wide studies, including one locus on chromosome 16p11 containing the SH2B1 gene. Animal studies have suggested that SH2B1 is a physiological enhancer of the insulin receptor and humans with rare deletions or mutations at SH2B1 are obese with a disproportionately high insulin resistance. Thus, the role of SH2B1 in both obesity and insulin resistance makes it a strong candidate for T2D. However, published data on the role of SH2B1 variability on the risk for T2D are conflicting, ranging from no effect at all to a robust association. METHODS: The SH2B1 tag SNP rs4788102 (SNP, single nucleotide polymorphism) was genotyped in 6978 individuals from six studies for abnormal glucose homeostasis (AGH), including impaired fasting glucose, impaired glucose tolerance or T2D, from the GENetics of Type 2 Diabetes in Italy and the United States (GENIUS T2D) consortium. Data from these studies were then meta-analyzed, in a Bayesian fashion, with those from DIAGRAM+ (n = 47,117) and four other published studies (n = 39,448). RESULTS: Variability at the SH2B1 obesity locus was not associated with AGH either in the GENIUS consortium (overall odds ratio (OR) = 0.96; 0.89-1.04) or in the meta-analysis (OR = 1.01; 0.98-1.05). CONCLUSION: Our data exclude a role for the SH2B1 obesity locus in the modulation of AGH.

TRIB3 R84 variant affects glucose homeostasis by altering the interplay between insulin sensitivity and secretion.

AIMS/HYPOTHESIS: The results of studies on the genetics of complex traits need to be replicated and to reach robust statistical significance before they can be considered as established. We here tried to replicate the previously reported association between the TRIB3 Q84R polymorphism (rs2295490) and glucose homeostasis. METHODS: Three samples of Europeans with fasting glucose <7.0 mmol/l were studied. In sample 1 (n=791), the association between TRIB3 Q84R and impaired glucose regulation (IGR; defined as impaired fasting glucose and/or impaired glucose tolerance and/or type 2 diabetes by OGTT) and insulin sensitivity (ISI), and its interplay with early-phase insulin secretion (i.e. disposition index [DI]) were analysed. Sample 2 (n=374) and sample 3 (n=394) were used to replicate the association with IGR and insulin sensitivity (by glucose clamp), respectively. Genotyping was performed by TaqMan allele discrimination. RESULTS: R84 carriers were at higher risk of IGR: OR for the additive model 1.54, p=0.004, and 1.63, p=0.027, in samples 1 and 2, respectively. In sample 1, both ISI (p=0.005) and DI (p=0.043) were progressively lower from QQ to QR and RR individuals. A 'triangulation approach' indicated that the association with IGR was mostly mediated by DI rather than by ISI changes (i.e. being the expected ORs 1.51 and 1.25, respectively). In sample 3, glucose disposal was 38.8+/-17.7, 33.8+/-14.4, and 31.6+/-13.3 micromol min(-1)kg(-1), p=0.022, in QQ, QR and RR individuals, respectively. CONCLUSIONS/INTERPRETATION: Our data confirm that the TRIB3 R84 variant affects glucose homeostasis and suggest this effect is due to an alteration of the interplay between insulin sensitivity and secretion.

A polymorphism (K121Q) of the human glycoprotein PC-1 gene coding region is strongly associated with insulin resistance.

The genes responsible for insulin resistance are poorly defined. Plasma cell differentiation antigen (PC-1) glycoprotein inhibits insulin receptor signaling and is associated with insulin resistance. We describe here a novel polymorphism in exon 4 of the PC-1 gene (K121Q) and demonstrate that it is strongly associated with insulin resistance in 121 healthy nonobese (BMI <30 kg/m2) nondiabetic (by oral glucose tolerance test [OGTT]) Caucasians from Sicily. Compared with 80 KK subjects, Q allele carriers (n = 41, 39 KQ and 2 QQ) showed higher glucose and insulin levels during OGTT (P < 0.001 by two-way analysis of variance) and insulin resistance by euglycemic clamp (M value = 5.25 +/- 1.38 [n = 24] vs. 6.30 +/- 1.39 mg x kg(-1) x min(-1) [n = 49], P = 0.005). Q carriers had higher risk of being hyperinsulinemic and insulin resistant (odds ratio [CI]: 2.99 [1.28-7.0], P < 0.001). Insulin receptor autophosphorylation was reduced (P < 0.01) in cultured skin fibroblasts from KQ versus KK subjects. Skeletal muscle PC-1 content was not different in 11 KQ versus 32 KK subjects (33 +/- 16.1 vs. 17.5 +/- 15 ng/mg protein, P = 0.3). These results suggest a cause-effect relationship between the Q carrying genotype and the insulin resistance phenotype, and raise the possibility that PC-1 genotyping could identify individuals who are at risk of developing insulin resistance, a condition that predisposes to type 2 diabetes and coronary artery disease.

Evidence for genetic epistasis in human insulin resistance: the combined effect of PC-1 (K121Q) and PPARgamma2 (P12A) polymorphisms.

Insulin resistance is believed to be under the control of several genes often interacting each other. However, whether genetic epistasis does in fact modulate human insulin sensitivity is unknown. In 338 healthy unrelated subjects from Sicily, all nondiabetic and not morbidly obese, we investigated whether two gene polymorphisms previously associated with insulin resistance (namely PC-1 K121Q and PPARgamma2 P12A) affect insulin sensitivity by interacting. PC-1 X121Q subjects showed higher level of fasting glucose, lower insulin sensitivity (by both the Matsuda insulin sensitivity index and M values at clamp, the latter performed in a subgroup of 113 subjects representative of the overall cohort) and higher insulin levels during the oral glucose tolerance test (OGTT) than PC-1 K121K subjects. In contrast, no difference in any of the measured variables was observed between PPARgamma2 P12P and X12A individuals. The deleterious effect of the PC-1 X121Q genotype on each of these three variables was significant and entirely dependent upon the coexistence of the PPARgamma2 P12P genotype. Among PPARgamma2 P12P carriers also fasting insulin and glucose levels during OGTT were higher in PC-1 X121Q than in K121K individuals. In contrast, no deleterious effect of the PC-1 X121Q genotype was observed among PPARgamma2 X12A carriers; rather, in these subjects a lower body mass index and consequently lower fasting insulin level was observed in PC-1 X121Q than in K121K carriers. Overall, a significant interaction between the two genes was observed on body mass index, insulin levels (both fasting and after OGTT) and both insulin sensitivity (i.e., insulin sensitivity index and M value) and insulin secretion (i.e., HOMA-B%) indexes.

The Q121 PC-1 variant and obesity have additive and independent effects in causing insulin resistance.

PC-1 is a membrane glycoprotein that impairs insulin receptor function. Its K121Q polymorphism is a genetic determinant of insulin resistance. We investigated whether the PC-1 gene modulates insulin sensitivity independently of weight status (i.e. both in nonobese and obese individuals). Nondiabetic subjects [164 males, 267 females; age, 37 +/- 0.6 yr, mean +/- SEM; body mass index (BMI), 32.7 +/- 0.5 kg/m(2)], who were subdivided into 220 nonobese (BMI < or = 29.9) and 211 obese, were studied. Although subjects were nondiabetic by selection criteria, plasma insulin concentrations during oral glucose tolerance test were higher (P < 0.05) in Q allele-carrying subjects (K121Q or Q121Q genotypes), compared with K121K individuals, in both the nonobese and obese groups. Insulin sensitivity, measured by euglycemic clamp in a representative subgroup of 131 of 431 randomly selected subjects, progressively decreased (P < 0.001) from nonobese K121K [n = 61; glucose disposal (M) = 34.9 +/- 1.1 micromol/kg/min] to nonobese Q (n = 21; M = 29.9 +/- 2.0), obese K121K (n = 31, M = 18.5 +/- 1.2), and obese Q (n = 18, M = 15.5 +/- 1.2) carriers. The K121Q polymorphism was correlated with insulin sensitivity independently (P < 0.05) of BMI, gender, age, and waist circumference. In conclusion, the Q121 PC-1 variant and obesity have independent and additive effects in causing insulin resistance.

A soluble PC-1 circulates in human plasma: relationship with insulin resistance and associated abnormalities.

An increased tissue content of PC-1, an inhibitor of insulin receptor signaling, may play a role in insulin resistance. Large scale prospective studies to test this hypothesis are difficult to carry out because of the need for tissue biopsies. The aim of this study was to investigate whether PC-1 is measurable in human plasma and whether its concentration is related to insulin sensitivity. A soluble PC-1, with mol wt and enzymatic activity similar to those of tissue PC-1, was measurable in human plasma by a specific enzyme-linked immunosorbent assay and was inversely correlated to skeletal muscle PC-1 content (r = -0.5; P < 0.01). The plasma PC-1 concentration was decreased (P < 0.05) in insulin-resistant (22.7 +/- 3.0 ng/mL; n = 25) compared to insulin-sensitive (36.7 +/- 4.5; n = 25) nondiabetic subjects and was correlated negatively with the waist/hip ratio (r = -0.48; P < 0.001) and mean blood pressure (r = -0.3; P < 0.05) and positively with high density lipoprotein/total cholesterol (r = 0.38; P < 0.01) and both the M value and the plasma free fatty acid level decrement at clamp studies (r = 0.28; n = 50; P = 0.05 and r = 0.43; n = 22; P < 0.05, respectively). A plasma PC-1 concentration of 19 ng/mL or less identified a cluster of insulin resistance-related alterations with 75% accuracy. In conclusion, PC-1 circulates in human plasma, and its concentration is related to insulin sensitivity. This may help to plan studies aimed at understanding the role of PC-1 in insulin resistance.

Dynamic performance of a load-moving skeletal muscle.

The dynamic response of the tibialis anterior muscle of the cat was determined while it was subjected to sinusoidally varying orderly stimulation of motor units and to different isotonic loads in the range of 14-85% of the maximal isometric force. The dynamic response consisted of three major components: the displacement gain, the displacement attenuation, and a pure time delay. The displacement gain was dependent on the passive load applied to the muscle and the active force generated during contraction, which could be determined from the length-tension relationships and the corresponding shortening velocity. In general, the load displacement decreased as the load mass increased from 25 to 85% of the maximal isometric force. For loads less than 25% of the maximal isometric force, slight decrease in displacement was consistently observed. The displacement attenuation was dependent on the contraction frequency but uniform for all the load masses applied to the muscle. A pure time delay of 5 ms was present and accounted for various physiological processes such as conduction time in nerve and muscle, neuromuscular junction transmission, and excitation-contraction coupling. A quantitative equation was developed to describe the muscle's dynamic response under isotonic conditions and for a wide range of loads for use in various applications.

Load, length, and velocity of load-moving tibialis anterior muscle of the cat.

Three-dimensional relationships of load, length, and velocity of shortening of the tibialis anterior muscle in the cat were derived experimentally and fitted with an analytic model. Gravitational loads were applied to the isolated muscle, which arrived at an equilibrium with the passive forces before supramaximal tetanic stimulation was delivered to its nerve. Recordings of initial passive muscle length at equilibrium and length changes throughout the shortening phase up to the final length at active equilibrium were taken and numerically differentiated to obtain each load's instantaneous velocity. A three-dimensional surface was constructed by using instantaneous length and the corresponding velocity for each of several loads. Maximal velocity of shortening was shown to gradually decrease, occurring earlier in the shortening phase (at larger muscle lengths) as loads increased. Whereas load-velocity curves were hyperbolic for middle and short muscle lengths, they were nonmonotonic during shortening above the optimal length. The model was found to correlate well with the experimental data (R = 0.98) and allowed for prediction of both muscle performance boundaries and instantaneous shortening velocity for a given length across the physiological load spectrum, thus offering a realistic estimation of the contractile properties exhibited by the tibialis anterior muscle in functions similar to naturally occurring movements against gravitational loads, which are accelerated and decelerated during the movement.

Role of tendon properties on the dynamic performance of different isometric muscles.

The effect of the tendon's viscoelastic stiffness on the dynamic performance of muscles with different architecture was determined using the cat's medial gastrocnemius and extensor digitorum longus. Dynamic response models were derived under sinusoidal contraction-relaxation in the range of 0.4-6.0 Hz and between 20 and 80% of the muscles' maximal isometric tension, manipulated by orderly recruitment-derecruitment of motor units together with firing rate increase-decrease. It was shown that, for isometric contractions at the muscle's optimum length, the dynamic response of the muscles was not significantly different before and after dissection of the tendon. Therefore the conclusion that under these conditions the tendon acts like a stiff force transmitter without significantly modifying the muscle's performance was confirmed and extended to muscles with different architecture.

Electromyogram power spectra frequencies associated with motor unit recruitment strategies.

The isolated contributions of motor unit recruitment and firing rate variations to the median frequency of the electromyogram's power density spectrum were determined. Orderly stimulation of the cat gastrocnemius motor units via nerve electrodes gave rise to linearly increasing median frequency regardless of the action potential firing rate of the active motor units. Increase in the discharge rate of all the motor units resulted in nearly constant median frequency. It was concluded that the increasing average conduction velocity during motor unit recruitment is the major contributor to variations in the electromyogram median frequency. The possibility of using the median frequency as the index to identify the recruitment control strategies employed by various muscles during increasing force contraction is suggested.

Method to impact in vivo rabbit femoral cartilage with blows of quantifiable stress.

The purpose of this study was to develop a technique by which a known stress could be applied uniformly across the femoral cartilage of a rabbit as a model for the development of post-traumatic arthritis. A system to impact the cartilage was designed that consisted of an apparatus to deliver a blow of quantifiable force, a method to apply the stress uniformly over the impact area, and a way to accurately measure the impact area. The knee joints of cadaveric New Zealand White rabbits were surgically exposed with the knee flexed so that the distal femoral articular surface was perpendicular to an impactor. With the knee fixed in position, a cup containing polymethylmethacrylate bone cement was applied to create an exact contour of the femoral surface, and the cement was allowed to cure. The form was then rested on the rabbit knee, and a drop tower released a weight of known mass from a known height onto an impactor (instrumented with strain gauges to measure the compressive force) that was attached to the cup. The area of the impacted surface was determined and, with the measured force, was used to calculate an accurate estimate of the impact stress. This method can be performed under sterile conditions, and therefore it is well suited for survival experiments in which the long-term effects of impact to cartilage will be studied.

The dynamic performance model of skeletal muscle.

Applications of electrical stimulation to the nerve or muscles associated with a defunct limb joint due to stroke or spinal cord injury are a viable means of restoring a certain level of functional movement to the patient. In this article, the currently acceptable physiology of motor control is outlined and used as a criterion for electrophysiological and biomechanical performance evaluation of contemporary electrical stimulation strategies used by various systems attempting to duplicate such motor control in an effort to restore meaningful limb function. Strategies associated with surface, nerve, intramuscular, and reflex stimulation are critically reviewed with special reference to voluntary sensory motor control of a limb joint rather than an isolated muscle.

The role of the hamstrings in the rehabilitation of the anterior cruciate ligament-deficient knee in athletes.

There is ample evidence for the synergy between the knee musculature and ligaments, and the overall maintenance of joint integrity. In fact it could be reasonably concluded that the joint's antagonist muscle acts as a 'regulator' compensating for various internal and external disturbances of the intended movement. Undoubtedly, well conditioned muscles provide substantial improvements in joint stiffness and laxity, and reduce the risk of ligamentous injuries in the elite athlete. More research is needed to delineate the details of the questions which this new approach raises.

The effect of placing a tensioned graft across open growth plates. A gross and histologic analysis.

BACKGROUND: Midsubstance tears of the anterior cruciate ligament in skeletally immature patients are increasingly common and are a challenging problem. The results of nonoperative treatment are no better in children than they are in adults. Physeal-sparing reconstructive procedures have yielded poor results. Reconstructive procedures that are utilized in adults violate the physis, potentially resulting in growth abnormalities. The objective of this study was to provide a model for reconstruction of the anterior cruciate ligament in skeletally immature patients by evaluating the effects of a tensioned connective-tissue graft placed across the canine physis. METHODS: Twelve ten-week-old beagles underwent reconstruction of the anterior cruciate ligament consisting of placement of fascia lata autograft through drill-holes across the femoral and tibial physes, tensioning of the graft to 80 N, and fixing it with screws and washers. The contralateral limb served as a control. One dog was eliminated from the study secondary to a postoperative infection. Four months postoperatively, the dogs were killed and were inspected grossly, radiographically, and histologically for any evidence of growth disturbance. RESULTS: Significant valgus deformity of the distal part of the femur (p < 0.001) and significant varus deformity of the proximal part of the tibia (p = 0.03) developed in the treated limbs. Neither radiographic nor histologic examination demonstrated any evidence of physeal bar formation. CONCLUSIONS: Significant growth disturbances occur with excessively tensioned transphyseal reconstruction of the anterior cruciate ligament in the canine model. These growth disturbances occur without radiographic or histologic evidence of physeal bar formation.

The effect of tendon viscoelastic stiffness on the dynamic performance of isometric muscle.

The effect of tendons viscoelastic stiffness on the dynamic response of the cat's tibialis anterior muscle under isometric conditions was determined. It was shown that the dynamic response model of the muscle derived under sinusoidal contraction-relaxation in the range of 20-80% of its maximal isometric tension was not statistically different before and after the disection of the whole distal tendon. It was suggested that under isometric conditions in the force range of 20-80% of the maximal, the tendon acts as a very stiff force transmission linkage without significantly modifying the muscle's performance.

The isometric length-force models of nine different skeletal muscles.

The length-force relations of nine different skeletal muscles in the hindlimb of the cat were determined experimentally, with electrical stimulation of the sciatic nerve as the activation mode. It was shown that the active-, passive-, and total-force patterns varied widely among the muscles. The tibialis posterior (TP), medial and lateral gastrocnemius (MG, LG) and flexor digitorum longus (FDL) had a symmetric active-force curve, whereas the tibialis anterior (TA), peroneus brevis (PB), peroneus longus (PL), extensor digitorum longus (EDL), and soleus (SOL) had an asymmetric curve which exhibits about 25% of the maximal isometric force at extreme lengths. The SOL, EDL, and LG had a low-level passive force which appeared at short muscle length, whereas all other muscles exhibited initial passive force just before the optimal length. The total force was rising quasi-linearly for the SOL, whereas the other muscles exhibited an intermediate plateau about the optimal length. The LG and FDL had a substantial but temporary intermediate dip in the total force as the muscle was elongated past the optimal length. The elongation range of the various muscles also varied, ranging from +/- 15 to +/- 30% of the optimal length. The elongation range was symmetric for the FDL, LG, MG, TP, SOL, and EDL, and asymmetric for the PL, PB, and TA, being -12 to + 17%, -12 to + 17%, and -35 to + 12%, respectively. Two different models which incorporate muscle architecture were successfully fitted to the experimental data of the muscles except for the MG and TA. The architecture of these two muscles is highly nonhomogeneous and contains compartments with two pennation patterns or two different optimal lengths. New models, which add spatially and temporally the individual characteristics of each compartment of the muscles, were constructed for these two muscles. The new models demonstrated high correlation to the experimental data obtained from the MG and TA. It was concluded that the length-force relation varies widely among various skeletal muscles and is probably dependent on the primary function of the muscle in the context of integrated movement; this is a manifestation of architectural factors such as fiber pennation pattern and angle, cross-sectional area, ratio of muscle to tendon length, distribution of the fiber length within the muscle and compartmental pennation.

Frequency-dependent changes in neuromuscular responses to cyclic lumbar flexion.

Repetitive lifting in the workplace has been identified to be a cause of low back disorders. Epidemiologic data further supports an hypothesis that higher repetition rate (i.e. frequency) is an added risk factor. The objective of this study was to provide experimental data testing the above hypothesis. An in vivo feline model was subjected to 20-min of cyclic lumbar loading at frequencies of 0.1 Hz and 0.5 Hz while monitoring the EMG from the L-3/4-L-5/6 multifidus muscles and the creep at the L-4/5 level. Seven hours of rest were allowed after the cyclic flexion/extension was terminated. During this rest period, a single test cycle was performed every hour to assess recovery of EMG and lumbar creep. The results demonstrate that cyclic lumbar flexion elicits a transient neuromuscular disorder consisting of EMG spasms during the cyclic loading and initial and delayed muscular hyperexcitabilities during the rest period. Cyclic loading at 0.5 Hz resulted in significant (p<0.05) increase in the hyperexcitability magnitude and duration during the recovery period. It was concluded that repetitive lumbar loading at fast rates is indeed a risk factor as it induces larger creep in the lumbar viscoelastic tissues which in turn intensify the resulting neuromuscular disorder.