Repetitions Of Squat Research Articles

Metabolic Responses to Weight Lifting

Metabolic Responses to Weight Lifting

Effects of the Occlusal Thickness of Mouthpieces on Salivary Cortisol during Resistance Strength Training

Background: When worn during exercise, it has been suggested that a mouthpiece may have a benefit to the athlete by increasing strength and endurance. Specifically, the use of a mouthpiece during resistance strength training has been shown to result in reduced post-exercise concentrations of cortisol when compared to no mouthpiece. The purpose of this pilot study is to determine if the thickness of the biting (occlusal) surface of the mouthpiece has an effect on the reduction of postexercise cortisol concentrations. Methods and findings: Six male (aged 22-25 years) participants performed identical one-hour workouts of strength training exercises consisting of five sets of five repetitions of back squats, bench press, deadlifts, and military press with 90 seconds of rest between sets. Each participant completed three total workouts while wearing either a mouthpiece with an occlusal thickness of 2 mm, of 6 mm, or no mouthpiece (control). Free cortisol concentrations were measured from salivary samples collected at four times during each workout; pre-workout, 30 min into the workout, immediately following the completion of the workout, and 10 min post-workout. Statistical significance was determined at α=0.05. Conclusion: While there was no statistical significance found amongst the results, there is a trend that follows previous research that the use of a mouthpiece during resistance strength training yields a reduced salivary cortisol concentration at 10 min post-workout when compared to no mouthpiece, suggesting that the thicker, 6 mm mouthpiece may be more effective. This finding suggests that the effect of a mouthpiece on athletic performance may be dependent on the occlusal thickness, which warrants further research into the optimal design for an athletic mouthpiece.

Vitamin D supplementation affects the IGF system in men after acute exercise

ObjectiveContradictory data between the Insulin-Like Growth Factor System (IGF) system and exercise may be due to alteration in IGF binding proteins. Vitamin D (D) deficiency has been related to muscle weakness and Insulin Like Growth Factor Binding Protein 3 (IGFBP3). A Vit. D and acute exercise merge is proposed to modify the IGF system. DesignD insufficient and deficient men (39.0±8.6yo with serum D (25OH D) 20.0±7.7ng/mL) did 1h of stretching (ST), aerobic (AB), and resistance (RT) exercises, before and after 28d of 4000IU/d Vit. D3 (D, n=6) or Placebo (P, n=7). ST, a time/attention control visit, interchanged unreceptive movements. AB was moderate intensity treadmill walking. RT rotated moderate strength 50% 1-RM repetitions (15, 10) of squat, bench press, leg press, and lat pull down. Serum Total IGF1 (TIGF1), Insulin Like Growth Factor Binding Protein 1 (IGFBP1), and IGFBP3 were measured before (T1, fasting), immediately after (T2), and 2h post (T3) exercise. ResultsAfter ST, IGFBP3 was greater in the D group at T2 (2948, 2130ng/mL; p<0.03) and T3 (3087, 2212; p<0.02). During RT, TIGF1 decreased in the Placebo (P) group from T1 to T3 (151.4, 107.3ng/mL; p<0.05), while IGFBP1 increased in the D group from T1 to T3 (26.5, 96.2ng/mL; p<0.05). RT IGFBP3 was greater at T1, T2, and T3 in the D group (2932.5, 2110.7; p<0.03), (3163.9, 2392.5; p<0.04), and (3355.3, 2353.1; p<0.01). In AB, IGFBP3 was greater in the D group at T2 (3128.6, 2226.3.0; p<0.04) and T3 (2949.7, 2135.1; p<0.05). ConclusionD supplementation amplified IGFBP3 after low or moderate activity which may increase the delivery of IGF1 to tissues. Resistance exercise with D not only increased IGFBP3 and IGFBP1 levels but also conserved TIGF1 levels, possibly shifting the IGF system for enriched muscle well-being.

Ingestion of High Molecular Weight Carbohydrate Enhances Subsequent Repeated Maximal Power: A Randomized Controlled Trial.

Athletes in sports demanding repeat maximal work outputs frequently train concurrently utilizing sequential bouts of intense endurance and resistance training sessions. On a daily basis, maximal work within subsequent bouts may be limited by muscle glycogen availability. Recently, the ingestion of a unique high molecular weight (HMW) carbohydrate was found to increase glycogen re-synthesis rate and enhance work output during subsequent endurance exercise, relative to low molecular weight (LMW) carbohydrate ingestion. The effect of the HMW carbohydrate, however, on the performance of intense resistance exercise following prolonged-intense endurance training is unknown. Sixteen resistance trained men (23±3 years; 176.7±9.8 cm; 88.2±8.6 kg) participated in a double-blind, placebo-controlled, randomized 3-way crossover design comprising a muscle-glycogen depleting cycling exercise followed by ingestion of placebo (PLA), or 1.2 g•kg•bw-1 of LMW or HMW carbohydrate solution (10%) with blood sampling for 2-h post-ingestion. Thereafter, participants performed 5 sets of 10 maximal explosive repetitions of back squat (75% of 1RM). Compared to PLA, ingestion of HMW (4.9%, 90%CI 3.8%, 5.9%) and LMW (1.9%, 90%CI 0.8%, 3.0%) carbohydrate solutions substantially increased power output during resistance exercise, with the 3.1% (90% CI 4.3, 2.0%) almost certain additional gain in power after HMW-LMW ingestion attributed to higher movement velocity after force kinematic analysis (HMW-LMW 2.5%, 90%CI 1.4, 3.7%). Both carbohydrate solutions increased post-exercise plasma glucose, glucoregulatory and gut hormones compared to PLA, but differences between carbohydrates were unclear; thus, the underlying mechanism remains to be elucidated. Ingestion of a HMW carbohydrate following prolonged intense endurance exercise provides superior benefits to movement velocity and power output during subsequent repeated maximal explosive resistance exercise. This study was registered with clinicaltrials.gov (NCT02778373).

The Effects of Supplementation with p-Synephrine Alone and in Combination with Caffeine on Metabolic, Lipolytic, and Cardiovascular Responses during Resistance Exercise

Objective: The purpose of this study was to examine the metabolic, lipolytic, and cardiovascular responses to supplementation with p-synephrine alone and in combination with caffeine during resistance exercise (RE).Methods: Twelve healthy men performed a control RE protocol (6 × 10 repetitions of squats) and were randomly assigned (using a double-blind crossover design with random protocol sequencing) to a supplement sequence: p-synephrine (S; 100 mg), p-synephrine + caffeine (SCF; 100 mg of p-synephrine plus 100 mg of caffeine), or a placebo (P). Subjects reported to the lab at a standard time, consumed a supplement, sat quietly for 45 minutes, performed the RE protocol, and sat quietly for 30 minutes. Blood samples were collected at rest (T1), after sitting quietly for 45 minutes (T2), immediately following RE (T3), and 15 minutes (T4) and 30 minutes (T5) postexercise. Oxygen consumption (VO2) and heart rate (HR) data were collected throughout. Results: Serum glycerol was significantly elevated at T2 only in S and SCF and T3 to T5 in all treatments. Nonesterified fatty acid (NEFA) concentrations did not differ between treatments. Plasma glucose was significantly elevated compared to T1 with highest area under the curve values seen in SCF. Mean VO2 and energy expenditure (EE) were significantly higher in S and SCF through 30 minutes postexercise. Fat oxidation rates favored S and SCF between 25 and 30 minutes postexercise. Mean HR during RE was significantly highest in SCF.Conclusions: Supplementation with S and SCF increases lipolysis primarily at rest and increases VO2, EE, and fat oxidation rates 30 minutes following RE. No HR changes were observed unless caffeine was added.

Kinesiology Tape or Compression Sleeve Applied to the Thigh Does Not Improve Balance or Muscle Activation Before or Following Fatigue.

Cavanaugh, MT, Quigley, PJ, Hodgson, DD, Reid, JC, and Behm, DG. Kinesiology tape or compression sleeve applied to the thigh does not improve balance or muscle activation before or following fatigue. J Strength Cond Res 30(7): 1992-2000, 2016-Compression sleeves (CS) and kinesiology tape (KT) are purported to enhance proprioception, however, there is substantial conflict in the literature. Because the beneficial effects of CS and KT are more evident in the literature with recovery, the objective of this study was to examine the effects of CS and KT on balance under acute nonfatigued and postfatigued conditions. Using a within-subject, repeated-measures design, 12 university participants (5 females and 7 males) performed in a random order CS, KT, and Control conditions. Two trials of each test were conducted before the application of CS or KT (pretest 1), immediately after the application (pretest 2), with posttests at 1 and 10 minutes after 4 sets of unilateral Bulgarian squats to failure (1 minute rest between sets). Tests included a Y balance test (measures: distance reached by nondominant foot in anterior, posterior lateral, and posterior medial directions) and drop jump landing balance test from a 50-cm platform (measures: ground reaction force, electromyography, and center of pressure). The fatigue protocol induced 25.3% decrease in unilateral squat repetitions from set 1 to set 4. There were no significant condition main effects or interactions for any balance measure or EMG before or after fatigue. In conclusion, independent of fatigue, there was no significant effect of CS or KT on balance outcomes immediately and up to 10 minutes following the fatiguing intervention. Thus, nonfatigued or muscles weakened by fatigue did not benefit from CS and KT application.

Sustainability and repeatability of postactivation potentiation.

This study investigated the duration and repeatability of postactivation potentiation (PAP) benefits within a single exercise session. Specifically examined were the recurring effects, over multiple sets, of heavy back squats on repeated sprint times. A partially randomized, counterbalanced, repeated measures design was implemented using 29 college-aged male NCAA varsity field sport athletes participating in PAP and control conditions. Subjects performed four repetitions of back squats (PAP=90% 1RM; control =20% 1RM), rested 8 minutes, performed a set of four 40-m sprints (55 s inter-repetition active recovery) and rested for 8 minutes after the last sprint. This was performed two more times, for a total of three sets (of back squats and sprints) performed 20 minutes apart. Sprint performance was measured using electronic timing gates and a timing pad to capture of reaction time (RT) at the start of each sprint. 2x3 (condition x sets) and 2x4 (condition X repetition) repeated measures ANOVAs were used to analyze both sprint and RT outcomes. Subjects ran significantly faster (P<0.05) after PAP than control. Specifically, sprint times were faster for the first two-three sprints, but not the fourth, across all three sets of sprints over the 51-min exercise session. RT was not affected (P>0.05) by PAP activity. The PAP effect was sustainable up to 11 minutes after heavy back squats and was repeated successfully three times. These findings can assist coaches and athletes interested in applying PAP to improve performance.

Comparison Of Muscle Activation Using A Nitrogen Piston-based Resistance Device With Free Weights

Resistance training is especially important for populations at risk of sarcopenia and osteopenia such as older adults or astronauts working in microgravity. A limitation of common forms of resistance training is that they are gravity-based and lack efficacy in microgravity. Therefore, to maintain muscle and bone mass in microgravity, an alternative solution must be sought. One alternative is the use of a gas-filled piston-based resistance training system. PURPOSE: The goal of the current study is to assess the effectiveness of a Nitrogen-filled piston-based resistance training system (NitroForce) compared to isotonic resistance training. METHODS: Thirty recreational athletes performed five repetitions of squat and toe-raise exercises, in two experimental conditions: NitroForce and Isotonic. The NitroForce condition was characterized by resistance of approximately 70% of the participant’s one repetition maximum (1RM) while resistance was supplied using the NitroForce system. Isotonic condition was characterized by participants performing each exercise with resistance equal to 70% of 1RM provided by free weights. Surface electromyography (sEMG, 1928 Hz, Delsys) was recorded from the vastus medialis (VM), vastus lateralis (VL), and the lateral (LG) and medial heads of the gastrocnemius (MG). Mean sEMG amplitude was quantified using the RMS (20 ms smoothing window) and normalized to MVC for each muscle in each condition. Paired samples t-tests were used to compare mean sEMG values. Significance was set at p < 0.05. RESULTS: In the squat exercise, VM activation was significantly greater in the NitroForce compared to isotonic condition (p = 0.039), but no differences were observed in the VL (p = 0.367). No significant differences were observed between the NitroForce and isotonic conditions for the LG (p = 0.400) or MG (p = 0.442) in the toe-raise exercise. CONCLUSIONS: These data demonstrate that muscle activation intensity as measured by sEMG is not significantly different in the NitroForce compared to isotonic conditions. Therefore, the NitroForce provides a similar level of resistance and overload to standard isotonic resistance training loads. However, due to the non-gravity-based nature of the NitroForce, it may provide a better resistance training solution in microgravity environments.

The Relationship Between Bat Velocity And Measures Of Strength And Power In Ncaa Division Ii Baseball Players

PURPOSE: This study was designed to examine the relationship between measures of upper and lower-body strength and power components and instantaneous bat velocity in NCAA Division II Collegiate baseball players. METHODS: Ten Division II collegiate baseball players (age: 20.3 ± 1.3 years; mass: 89.6 ± 12.1 kg; average years of experience: 14.9 ± 1.6; 7 right-handed batters) volunteered to participate in this study. Each subject completed two days of testing with a week between test days. Day 1 consisted of 5 repetition maximum bench press, 5 repetition squat, and grip strength. Day 2 consisted of lower body power (vertical jump performed on a contact mat), upper-body power (plyometric pushup performed on a force plate) and instantaneous bat velocity testing. A 3D motion analysis system sampling at 200 Hz was used to record the instantaneous bat velocity with the players hitting a ball from a tee. Spearman rank correlations were performed to establish the magnitude of the relationships between the variables. RESULTS: The magnitude of the relationships between the measures of strength and power and bat velocity ranged from small to large (-0.103 to 0.583) and none were significant (p>0.05). The largest correlation was found between left-hand grip strength and instantaneous bat velocity (0.583). CONCLUSION: Findings from this study suggest the importance of possibly implementing hand grip training to aid in an increase in instantaneous bat velocity. Since the upper-body and lower-body strength components demonstrated only small correlations with bat velocity, training should consist of working on mechanical efficiency of the players swing once muscular strength and power have been developed.

Influence of Footwear Type on Barbell Back Squat Using 50, 70, and 90% of One Repetition Maximum: A Biomechanical Analysis.

The effect of footwear type was investigated during the barbell back squat using three-dimensional motion analysis and ground reaction force data. Nine male participants (mean age = 26.4 ± 5.4 years, height = 1.79 ± 0.08 m, and mass = 84.7 ± 16.1 kg) completed 2 experimental testing sessions wearing 2 different forms of training footwear: (a) standard sports trainers (running shoes [RS]) and (b) specialized weightlifting shoes (WS). On each test day, participants completed a sequence of 5, 3, and 1 repetitions of a barbell back squat using 50, 70, and 90%, respectively, of their 1 repetition maximum (1RM) load in each of the shoe conditions. Shoe order, which was initially randomly assigned for test day 1, was reversed on test day 2. Significant main effects were found for peak dorsiflexion of both left (p < 0.001) and right (p < 0.001) ankles. Pairwise post hoc comparisons showed that the RS condition exhibited significantly more dorsiflexion compared with the WS condition in both left and right ankles. There was also a significant main effect of load (%1RM) within the left ankle (p < 0.01) with post hoc comparisons showing that there was a significant increase in peak dorsiflexion angle from 50 to 90% (p ≤ 0.05) and 70-90% of 1RM (p ≤ 0.05) but no difference between 50 and 70% of 1RM (p = 1.000). These findings indicate that further investigation is necessary to substantiate claims regarding the benefits of wearing WS during resistance training exercises targeting the squat movement.

Vascular Occlusion and Sequential Compression for Recovery After Resistance Exercise.

The purpose of this study was to evaluate vascular occlusion (OCC) and sequential intermittent pneumatic compression (SIPC) as recovery strategies after fatiguing resistance exercise. Twelve strength-trained male participants (age: 24.0 ± 6.3 years, height: 180.4 ± 9.7 cm, and weight: 84.8 ± 9.6 kg) participated in a randomized cross-over study. Participants performed a fatiguing resistance exercise bout consisting of 10 sets with 10 repetitions of back squats at 70% 1 repetition maximum with 3-minute rest between sets. Outcome measures of perceived recovery status, muscle soreness, concentric peak isokinetic torque of the quadriceps, squat jump (SJ) height, and countermovement jump (CMJ) height were taken before the fatiguing resistance exercise bout and repeated immediately post, 1 hour, and 24 hours later. Immediately after the postexercise measures, participants undertook 1 of the 3 recovery strategies: OCC, SIPC, and a passive control (CON). Concentric peak isokinetic torque of the quadriceps was decreased significantly immediately post and 1 hour after the fatiguing resistance exercise bout compared with baseline values (p ≤ 0.05). Mean SJ and CMJ jump height decreased significantly immediately post and 1 hour compared with baseline measures, but only the SJ was significantly decreased at 24 hours. There were no significant differences between conditions for any of the postexercise measures (p > 0.05). In conclusion, this study indicates that OCC and SIPC are not effective for attenuating muscle performance loss after a fatiguing resistance exercise bout relative to passive recovery.

Intra Complex Recovery Intervals for Acute Lower Body Post Activation Potentiation in Elite Badminton Athletes

1.1 Objectives: This study examined the acute effects of back squats on jump performance with a focus on the individual recovery interval for postactivation potentiation (PAP) through a discontinuous time course. 1.2 Methods: Eleven elite badminton athletes performed 3 countermovement jumps (CMJs) at 10 randomized and separate testing sessions, 3-12 mins after 3 repetitions of maximal back squats at 90% one-repetition maximum. Power output, force, velocity and jump height were determined for all CMJs. 1.3 Results: There was no significant main effect in CMJ kinetic variables across the time course of the recovery intervals. Percentage differences at each recovery interval revealed mostly insubstantial differences in peak power, mean power, peak force, peak velocity, mean velocity and jump height. Only mean force showed trivial to small improvements from baseline measures. Individual athletes attained maximal values for CMJ kinetic variables at different recovery intervals, yet this did not result in improvement of jumping performance. 1.4 Conclusion: Even though the potentiation of the mean response for jump kinetic variables at each recovery interval was mostly insubstantial, the considerable potentiation observed for individual athletes in power and jump height may warrant substantial advantage in athletic performance, making it prudent to pre-determine the optimal protocol to induce PAP to enhance jump performance.

The Limiting Joint During a Failed Squat: A Biomechanics Case Series.

This investigation examined the characteristics of a failed back squat. Subjects were instructed to perform 3 repetitions of a barbell squat with a 3 repetition maximum load while instrumented for biomechanical analyses and standing atop force platforms. Inverse dynamics calculations were used to determine the net joint moment (NJM) power, work, and energy of the hip, knee, and ankle. Five subjects failed to complete all 3 repetitions, allowing for comparisons between a successful and the failed repetition. Although the NJM power and work were lower at all 3 joints during the failed attempt, the only statistically significant differences were at the hip. These findings suggest that the energy generated by the hip joint NJM limited performance of the task. However, examination of the NJM energy generation over time on an individual basis uncovered some features that were masked by the aggregated group mean data. For some subjects, the knee NJM limited the movement. Additionally, negligible to modest compensations occurred between the hip and knee NJM: a decreased energy generated by one NJM was often accompanied by an increase in energy generated at the other. A limiting joint, or "weak link," may explain the failure to complete a lift. Interventions should address the limiting joint on an individual-specific basis and incorporate assistive exercises that target these deficiencies.

Effects of an Unstable Load on Force and Muscle Activation During a Parallel Back Squat.

Stability training has become commonplace in the strength and conditioning field. Although unstable surface training has been investigated, little is known regarding the efficacy of performing resistance exercises with an unstable load. The purpose of this study was to determine if performing a parallel back squat with an unstable load (weights suspended from the bar by an elastic band) produces greater ground reaction forces (GRFs) and muscle activation in the trunk and lower extremities than a stable condition (a normally loaded barbell). Fifteen resistance-trained males (age: 24.2 ± 3.4 years, mass: 83.4 ± 18.7 kg) completed 10 repetitions of the back squat, with 60% of their 1 repetition maximum in both stable and unstable conditions. Peak vertical GRF and the integrated muscle activity of the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, soleus, rectus abdominis, external oblique, and erector spinae muscles on the right side of the body were determined The unstable load resulted in a small (3.9%) but significant decrease in peak vertical GRF. The unstable load also produced greater muscle activation in the rectus abdominis, external oblique, and soleus. The findings of this study suggest that squatting with an unstable load will increase activation of the stabilizing musculature; and while force decrements were statistically significant, the decrease was so small it may not be relevant to practitioners.

Comparison of Two Methods to Measure Snatch and Front Squat Bar Velocity.

While bar displacement has traditionally been measured using camera-based methods, several portable systems using cords connecting directly to the bar are now available. Because many weight training exercises involve the bar moving in multiple planes, which may change across load intensity, the validity of using a linear position transducer (LPT) is of significance. PURPOSE: To compare camera and LPT measurement of vertical bar velocity during front squats and snatches. METHODS: Healthy men (n=7) aged 18 to 35yrs completed one test session during which two repetitions of the front squat and snatch at 50%, 60% and 80% of their reported one repetition maximum (1RM) were completed. Order of exercises performed was randomized. Simultaneous measurement of bar displacement was made by a 12 camera system (Vicon, Oxford, UK) and a LPT (Tendo Power Analyzing Unit, Tendo Power Machines, Slovak Republic), from which peak velocities were computed. Correlational and 95% limits of agreement (LOA) analyses were conducted between the two methods. RESULTS: Strong relationships were revealed between the methods for both the front squat (50%: r=.96, 60%: r=.90, 80%: r=.97) and snatch (50%: r=.92, 60%: r=.99, 80%: r=.99). Camera estimated peak velocities were significantly greater for front squat at 50% (P=.018) and 60% (P=.031) and snatch at 60% (P=.004) and 80% (P=.003). Bias and 95% LOA during the front squat were: .09±.18m/s (50%), .09±.17m/s (60%), and .04±.14m/s (80%). Bias and 95% LOA during the snatch were .10±.52m/s (50%), .28±.32m/s (60%), and .26 ± .28m/s (80%). CONCLUSION: Stronger agreement was evident for the front squat compared to the snatch, which may be explained by the complexity of the snatch lift as it involves a degree of curvature during the second pull and catch. This explanation is plausible given research showing bar curvature during the second pull and catch increases as loads increase. However, given the relative agreement between these measurement techniques, this work does suggest a portable system may be efficacious for use in non-laboratory settings. As this study engaged intermediate lifters, future research should examine the agreement between measurement approaches in elite level lifters, particularly as such lifters may be less likely to increase the curvature of bar trajectory during a snatch life.

The Effects of Acute Resistance Exercise on Arterial Stiffness in Strength-trained Men

Previous studies examining the effects of acute resistance exercise on central arterial stiffness have reported mixed results. Previous investigations have not included men with a history of resistance exercise training. PURPOSE: The purpose of this study was to examine the effects of acute resistance exercise (RE) on arterial stiffness and central blood pressure indices in strength-trained men. METHODS: Nine men (age 24 ± 6.2 yrs; training age 10.7 ± 6.8 yrs) completed a control (CS) and exercise testing session (ES). Carotid-femoral pulse wave velocity (cfPWV) and radial artery pulse wave analysis derivatives [central systolic blood pressure (SBP) and augmentation index (AIx75)] were assessed using the SphygmoCor device and software at baseline, immediately post, and 1, 2, 3, and 4 hours after a standard breakfast (440 kcal; 43% carbohydrate, 45% fat, 12% protein). In ES, RE (4 X 5 repetitions of back squat, bench press, deadlift, barbell row at 75-80% 1-RM) was performed two hours after the standard breakfast. In CS, participants rested for the entire period. A 2 X 6 ANOVA with repeated measures was computed (α < 0.05). RESULTS: Heart rate (HR) was higher at hour 3 (75.2 ± 13.5 bpm, p = 0.002) and hour 4 (59.7 ± 8.5 bpm, p = 0.01) in ES compared to CS (53.8 ± 8.1 and 51.0 ± 9.0 bpm, respectively). Central SBP was higher at hour 3 (96.4 ± 8.3 mmH, p = 0.05) in ES when compared to CS (91.3 ± 5.1 mmHg). AIx75 was greater at hour 3 (66 ± 2.8%, p = 0.003) during ES when compared to CS (-10.8 ± 9.1%). There were no differences in AIx75 between the ES and CS at hour 4 (p > 0.05). There were no differences in cfPWV between ES and CS at any time point (p > 0.05). CONCLUSIONS: Acute resistance exercise does not increase central arterial stiffness as assessed by the carotid-femoral PWV, but may temporarily increase augmentation index, in strength-trained young men.

Force production during squats performed with a rotational resistance device under stable versus unstable conditions.

[Purpose] Force production during a squat action on a rotational resistance device (RRD) under stable and unstable conditions. [Subjects and Methods] Twenty-one healthy males were asked to perform six sets of six repetitions of squats on an RRD on either stable or unstable surfaces. The stable and unstable sets were performed on different days. Muscular outputs were obtained from a linear encoder and a strain gauge fixed to a vest. [Results] Overall, the results showed no significant differences for any of the dependent variables across exercise modes. Forcemean outputs were higher in the concentric phase than in the eccentric phase for each condition, but there were no differences in velocity, time or displacement. The forcepeak was similar in the eccentric and concentric phases of movement under both stable and unstable conditions. There were no significant differences in forcemean between sets per condition or between conditions. [Conclusion] These results suggest that performing squats with a RRD achieves similar forcemean and forcepeak under stable and unstable conditions. The forcepeak produced is also similar in concentric and eccentric phases.

Foam rolling for delayed-onset muscle soreness and recovery of dynamic performance measures.

After an intense bout of exercise, foam rolling is thought to alleviate muscle fatigue and soreness (ie, delayed-onset muscle soreness [DOMS]) and improve muscular performance. Potentially, foam rolling may be an effective therapeutic modality to reduce DOMS while enhancing the recovery of muscular performance. To examine the effects of foam rolling as a recovery tool after an intense exercise protocol through assessment of pressure-pain threshold, sprint time, change-of-direction speed, power, and dynamic strength-endurance. Controlled laboratory study. University laboratory. A total of 8 healthy, physically active males (age = 22.1 ± 2.5 years, height = 177.0 ± 7.5 cm, mass = 88.4 ± 11.4 kg) participated. Participants performed 2 conditions, separated by 4 weeks, involving 10 sets of 10 repetitions of back squats at 60% of their 1-repetition maximum, followed by either no foam rolling or 20 minutes of foam rolling immediately, 24, and 48 hours postexercise. Pressure-pain threshold, sprint speed (30-m sprint time), power (broad-jump distance), change-of-direction speed (T-test), and dynamic strength-endurance. Foam rolling substantially improved quadriceps muscle tenderness by a moderate to large amount in the days after fatigue (Cohen d range, 0.59 to 0.84). Substantial effects ranged from small to large in sprint time (Cohen d range, 0.68 to 0.77), power (Cohen d range, 0.48 to 0.87), and dynamic strength-endurance (Cohen d = 0.54). Foam rolling effectively reduced DOMS and associated decrements in most dynamic performance measures.

Wearable system for auditory feedback based on real-time gait analysis: Application on patients with Parkinson's disease

(GA) at 100Hz (Viconmotion systems, UK; gait protocols [2,3]). 3D accelerometer and gyroscope datawere collected at 50Hz from the 5 sensors, and analysed by proprietary algorithms based onKalman and lowpass filters. The exercise and rest period sequences, and the targetmotion,were suggestedby an interfacewith audio andvisual feedbacks. Results: For each of the above mentioned exercises the knee and thorax angles were acquired from the two systems. A typical acquisition is shown in Fig. 1 where it can be seen that the subject performed 5 repetitions of squat in 70 s, moving the thorax on the sagittal plane between 0◦ and 45◦. The mean distance in degrees between the two systems was evaluated for each subject and each exercise and the average distances over time are shown in Table 1. The distance is also presented to provide the best and the worst measure for each exercise. Discussion: This work investigated the reliability of a modern rehabilitation system based on inertial sensors, whichwould allow for rehabilitation exercises to be performed in a variety of settings. The setting up was simple and fast, and the performance can be monitored at distance and reasonable costs. The results proved that the present system implies small motion errors at the knee and thorax, and therefore it can be utilized in routine practice after orthopaedic treatments.

Neuromuscular response differences to power vs strength back squat exercise in elite athletes.

The study's aim was to establish the neuromuscular responses in elite athletes during and following maximal 'explosive' regular back squat exercise at heavy, moderate, and light loads. Ten elite track and field athletes completed 10 sets of five maximal squat repetitions on three separate days. Knee extension maximal isometric voluntary contraction (MIVC), rate of force development (RFD) and evoked peak twitch force (Pt) assessments were made pre- and post-session. Surface electromyography [root mean square (RMS)] and mechanical measurements were recorded during repetitions. The heavy session resulted in the greatest repetition impulse in comparison to moderate and light sessions (P < 0.001), while the latter showed highest repetition power (P < 0.001). MIVC, RFD, and Pt were significantly reduced post-session (P < 0.01), with greatest reduction observed after the heavy, followed by the moderate and light sessions accordingly. Power significantly reduced during the heavy session only (P < 0.001), and greater increases in RMS occurred during heavy session (P < 0.001), followed by moderate, with no change during light session. In conclusion, this study has shown in elite athletes that the moderate load is optimal for providing a neuromuscular stimulus but with limited fatigue. This type of intervention could be potentially used in the development of both strength and power in elite athletic populations.