Changes In Rate Of Force Development Research Articles

Resistance Training–Induced Gains in Rate of Force Development Are Maintained During Training Cessation: A Meta-Analysis

ABSTRACT The present meta-analysis examined the effects of resistance training on increasing the rate of force development (RFD), followed by exploring the changes in RFD occurring during training cessation. Five databases were searched to find eligible studies. Their methodological quality was evaluated using the Downs and Black checklist. The data were pooled in a random-effects meta-analysis. Seven studies with 11 training groups were included in the meta-analysis. All studies were classified as being of good or moderate quality. Resistance training increased RFD (d: 0.24; 95% confidence interval [CI]: 0.09–0.38). There was no significant difference in RFD between the postintervention and postdetraining periods (d: −0.02; 95% CI: −0.10–0.06). In subgroup meta-analyses, there was no significant difference (all p > 0.05) between the postintervention and postdetraining RFD when categorized according to detraining duration (up to 4 weeks versus 7–16 weeks) or participants' training status (untrained versus trained). This meta-analysis demonstrated that resistance training effectively increases RFD. More importantly, the results also indicated that gains in RFD are maintained after detraining. Thus, unlike a few other resistance training–induced adaptations (e.g., increases in muscular strength and muscular endurance), it seems that gains in RFD are preserved during a detraining phase.

Comparison of The Effect of High- and Low-Frequency Vibration Foam Rolling on The Quadriceps Muscle.

Vibration foam rolling (VFR) intervention has recently gained attention in sports and rehabilitation settings since the superimposed vibration with foam rolling can affect several physiological systems. However, the sustained effect and a comparison of the effects of different VFR vibration frequencies on flexibility and muscle strength have not been examined. Therefore, in this study, we aimed to investigate the acute and sustained effects of three 60-s sets of VFR with different frequencies on knee flexion range of motion (ROM) and muscle strength of the knee extensors. Using a crossover, random allocation design, 16 male university students (21.2 ± 0.6 years) performed under two conditions: VFR with low (35 Hz) and high (67 Hz) frequencies. The acute and sustained effects (20 min after intervention) of VFR on knee flexion ROM, maximum voluntary isometric contraction (MVC-ISO) torque, maximum voluntary concentric contraction (MVC-CON) torque, rate of force development (RFD), and single-leg countermovement jump (CMJ) height were examined. Our results showed that knee flexion ROM increased significantly (p < 0.01) immediately after the VFR intervention and remained elevated up to 20 min, regardless of the vibration frequency. MVC-ISO and MVC-CON torque both decreased significantly (p < 0.01) immediately after the VFR intervention and remained significantly lowered up to 20 min, regardless of the vibration frequency. However, there were no significant changes in RFD or CMJ height. Our results suggest that VFR can increase knee flexion ROM but induces a decrease in muscle strength up to 20 min after VFR at both high and low frequencies.

Early Detection of Prolonged Decreases in Maximal Voluntary Contraction Force after Eccentric Exercise of the Knee Extensors.

We examined whether the magnitude of muscle damage indicated by changes in maximal voluntary isometric contraction (MVIC) strength 1 to 3 d after unaccustomed eccentric exercise (ECC) was correlated with changes in central and peripheral neuromuscular parameters immediately post-ECC. Twenty participants (19-36 yr) performed six sets of eight eccentric contractions of the knee extensors. Rate of force development (RFD) during knee extensor MVIC, twitch force, rate of force development (RFDRT) and rate of relaxation (RRRT) of the resting twitch, maximal M-wave (MMAX), voluntary activation, silent period duration, motor-evoked potentials (MEP) and short-interval intracortical inhibition were assessed before, immediately after, and 1 to 3 d post-ECC. Relationships between changes in these variables immediately post-ECC and changes in MVIC strength at 1 to 3 d post-ECC were examined by Pearson product-moment (r) or Spearman correlations. Maximal voluntary isometric contraction strength decreased (-22.2% ± 18.4%) immediately postexercise, and remained below baseline at 1 (-16.3% ± 15.2%), 2 (-14.7% ± 13.2%) and 3 d post-ECC (-8.6% ± 15.7%). Immediately post-ECC, RFD (0-30-ms: -38.3% ± 31.4%), twitch force (-45.9% ± 22.4%), RFDRT (-32.5% ± 40.7%), RRRT (-38.0% ± 39.7%), voluntary activation (-21.4% ± 16.5%) and MEP/MMAX at rest (-42.5% ± 23.3%) also decreased, whereas the silent period duration at 10%-MVIC increased by 26.0% ± 12.2% (P < 0.05). Decreases in RFD at 0 to 30 ms, 0 to 50 ms, and 0 to 100 ms immediately post-ECC were correlated (P < 0.05) with changes in MVIC strength at 1 d (r = 0.56-0.60) and 2 d post-ECC (r = 0.53-0.63). Changes in MEP/MMAX at 10%-MVIC immediately post-ECC were correlated with changes in MVIC strength at 1 d (r = -0.53) and 2 d (r = -0.54) post-ECC (P < 0.05). The magnitude of decrease in MVIC strength at 1 to 3 d after ECC was associated with the magnitude of changes in RFD and MEP/MMAX immediately post-ECC. However, based on individual data, these markers were not sensitive for the practical detection of muscle damage.

Hamstring strength and architectural adaptations following inertial flywheel resistance training

ObjectivesTo investigate the architectural and strength adaptations of the hamstrings following 6-weeks of inertial flywheel resistance training. DesignRandomised, stratified training intervention MethodsTwenty healthy males undertook 6-weeks of a conventional (n=10) or eccentrically biased (n=10) flywheel leg-curl training intervention as well as a subsequent 4-week detraining period. Biceps femoris long head (BFlh) architecture was assessed weekly, whilst assessments of eccentric and isometric knee flexor strength and rate of force development (RFD) were conducted prior to and following the intervention and detraining periods. ResultsThe participants who undertook the eccentrically biased flywheel intervention showed a significant 14±5% (p<0.001, d=1.98) increase in BFlh fascicle length after 6-weeks of training. These improvements in fascicle length subsequently declined by 13±4% (p<0.001. d=-2.04) following the 4-week detraining period. The conventional flywheel leg-curl training group saw no changes in BFlh fascicle length after the intervention (-0.5%±0.8%, p=0.939, d=-0.04) or detraining (-1.1%±1%, p=0.984, d=-0.03) periods. Both groups saw no changes in any of the strength or RFD variables after the intervention or the detraining period. ConclusionsFlywheel leg-curl training performed with an eccentric bias led to significant lengthening of BFlh fascicles without a change in RFD, eccentric or isometric strength. These increases in fascicle length were lost following a 4-week detraining period. Conventional flywheel leg-curl training resulted in no changes in fascicle length, strength and RFD. These findings suggest that additional eccentric bias is required during inertial flywheel resistance training to promote fascicle lengthening in the BFlh, however this may still be insufficient to cause alterations to strength and RFD.

Shod vs. Barefoot Effects on Force and Power Development During a Conventional Deadlift.

Hammer, ME, Meir, RA, Whitting, JW, and Crowley-McHattan, ZJ. Shod vs. barefoot effects on force and power development during a conventional deadlift. J Strength Cond Res 32(6): 1525-1530, 2018-The kinetics of a conventional deadlift in shod (S) vs. unshod (US) footwear conditions in 10 male participants (mean ± SD, age = 27.0 ± 5.8 years; body mass = 78.7 ± 11.5 kg; height = 175.8 ± 8.2 cm; 1 repetition maximum [1RM] deadlift = 155.8 ± 25.8 kg) was assessed in 2 testing sessions. A counterbalanced, cross-over experimental design was used with different loads (60 and 80% 1RM). Four sets of 4 repetitions were prescribed per session with 2 sets per shoe and with each shoe condition involving 1 set per load. Peak vertical force (PF), rate of force development (RFD), time to peak force (TPF), anterior-posterior (COP-AP) and mediolateral (COP-ML) center of pressure excursion, and barbell peak power data were recorded during all repetitions. Except for RFD (F = 6.389; p = 0.045; ηp = 0.516) and ML-COP (F = 6.696; p = 0.041; ηp = 0.527), there were no other significant main effects of shoe. There were significant main effects of load for PF (p ≤ 0.05), COP-AP (p = 0.011), TPF (p = 0.018), and COP-AP (p = 0.011). There were no significant interactions found between session, shoe, and load (p range from 0.944 to 0.086). Although the US condition may have produced changes in RFD and ML-COP compared with the shod condition, there is only limited evidence in the current study to support this lifting technique for the conventional deadlift. Further investigation is required to clarify any possible implications of this result and its benefit to lifters.

Associated decrements in rate of force development and neural drive after maximal eccentric exercise.

The present study investigated the changes in contractile rate of force development (RFD) and the neural drive following a single bout of eccentric exercise. Twenty-four subjects performed 15 × 10 maximal isokinetic eccentric knee extensor contractions. Prior to and at 24, 48, 72, 96, and 168 h during post-exercise recovery, isometric RFD (30, 50 100, and 200 ms), normalized RFD [1/6,1/2, and 2/3 of maximal voluntary contraction (MVC)] and rate of electromyography rise (RER; 30, 50, and 75 ms) were measured. RFD decreased by 28-42% peaking at 48 h (P < 0.01-P < 0.001) and remained depressed at 168 h (P < 0.05). Normalized RFD at 2/3 of MVC decreased by 22-39% (P < 0.01), peaked at 72 h and returned to baseline at 168 h. These changes in RFD were associated with a decrease in RER at 48 h-96 h (P < 0.05-P < 0.001). Accumulated changes (area under curve) revealed a greater relative decrease in accumulated RFD at 100 ms by -2727 ± 309 (%h; P < 0.05) and 200 ms by -3035 ± 271 (%h; P < 0.001) compared with MVC, which decreased, by -1956 ± 234 (%h). In conclusion, RFD and RER are both markedly reduced following a bout of maximal eccentric exercise. This association suggests that exercise-induced decrements in RFD can, in part, be explained decrements in neural drive.

Slackline Training for Balance and Strength Promotion

The prevalence of sustaining a sport injury is high in adults. Deficits in postural control/muscle strength represent important injury-risk factors. Thus, the purpose of this study was to investigate the impact of a specific type of balance training, i. e. slackline training, followed by detraining on balance and strength performance. Twenty-seven adults participated in this study and were assigned to an intervention (age 22.8±3.3 yrs) or a control group (age 23.9±4.4 yrs). The intervention group participated in 4 weeks of slackline training on nylon webbings. Detraining lasted 4 weeks. Tests included the measurement of (A) total centre of pressure displacements during one-legged standing on a balance platform and during the compensation of a perturbation impulse, (B) maximal torque and rate of force development (RFD) of the plantar flexors on an isokinetic device, and (C) jumping height on a force platform. After training, no significant interaction effects were observed for variables of static/dynamic postural control, maximal torque, and jumping height. Training-induced improvements were found for RFD. After the withdrawal of the training stimulus, RFD slightly decreased. Given that the promotion of balance and strength is important for injury prevention, changes in RFD only might not be sufficient to produce an injury-preventive effect.

Effects of Load and Contraction Velocity During Three-Week Biceps Curls Training on Isometric and Isokinetic Performance

The velocity-specificity principle in training is well established by studies applying isokinetic training devices. However, the contraction velocity during customary resistance training using barbells is rarely stable and can be manipulated in several ways. By manipulating load and intention of movement, the significance of contraction velocity during barbell training on gains in strength-related parameters was investigated. Twenty-seven subjects (divided into 3 experimental groups) performed standardized biceps curls 3 times a week for 3 weeks under the following conditions: high load and slow contraction velocity (HS), high load and fast contraction velocity (HF), and low load with fast contraction velocity (LF). Twelve subjects received no intervention, serving as controls (C). Elbow flexion strength was tested before and after the training period at both isometric and 4 isokinetic contraction velocities (30, 90, 240 and 300 degrees/sec) using a dynamometer. Rate of force development (RFD) was calculated in 100 millisecond epochs from isometric torque curves. Increased maximal isometric strength was seen in HF (9.7%), whereas HS improved slow isokinetic strength (8.5%). There were no improvements in force performance for LF and C. In none of the groups were changes in RFD observed. These findings support the principle of training specificity, highlighting the importance of details concerning contraction velocity on the outcome of resistance training using free weights.

Changes in muscle force–length properties affect the early rise of force in vivo

Changes in contractile rate of force development (RFD), measured within a short time interval from contraction initiation, were measured after a period of strength training that led to increases in muscle fascicle length but no measurable change in neuromuscular activity. The relationship between training-induced shifts in the moment-angle relation and changes in RFD measured to 30 ms (i.e., early) and 200 ms (i.e., late) from the onset of isometric knee extension force were examined; shifts in the moment-angle relation were used as an overall measure of changes in quadriceps muscle fascicle length. A significant proportion of the variance in RFD measured only in the initial contraction phase (0-30 ms) could be explained by shifts in the moment-angle relation (r=-0.66-0.71; R2=0.44-0.50). Training-induced increases in muscle fascicle length may lead to a reduced or complete lack of adaptive gains in contractile RFD, especially in the early contraction phase.