Transition to forefoot strike reduces load rates more effectively than altered cadence

Background: Excessive vertical impacts at landing are associated with common running injuries. Two primary gait-retraining interventions aimed at reducing impact forces are transition to forefoot strike and increasing cadence. The objective of this study was to compare the shortand long-term effects of 2 gait-retraining interventions aimed at reducing landing impacts.Methods: A total of 39 healthy recreational runners using a rearfoot strike and a cadence of 170 steps/min were randomized into cadence(CAD) or forefoot strike(FFS) groups. All participants performed 4 weeks of strengthening followed by 8 sessions of gait-retraining using auditory feedback. Vertical average load rates(VALR) and vertical instantaneous load rates(VILR) were calculated from the vertical ground reaction force curve. Both cadence and foot strike angle were measured using 3D motion analysis and an instrumented treadmill at baseline and at 1 week,1 month, and 6 months post retraining.Results: ANOVA revealed that the FFS group had significant reductions in VALR(49.7%) and VILR(41.7%), and changes were maintained long term. Foot strike angle in the FFS group changed from 14.2° dorsiflexion at baseline to 3.4° plantarflexion, with changes maintained long term. The CAD group exhibited significant reduction only in VALR(16%) and only at 6 months. Both groups had significant and similar increases in cadence at all follow-ups(CAD, +7.2% to 173 steps/min;and FFS, +6.1% to 172 steps/min).Conclusion: Forefoot strike gait-retraining resulted in significantly greater reductions in VALR and similar increases in cadence compared to cadence gait-retraining in the short and long term. Cadence gait-retraining resulted in small reductions in VALR at only the 6-month follow-up.     

Running speed-induced changes in foot contact pattern influence impact loading rate

Purpose. We aimed to determine the effect of speed-induced changes in foot contact patterns on the vertical instantaneous loading rate (VILR). We hypothesized that transition runners, i.e. runners that shift towards a mid- (MF) or forefoot contact pattern (FF) when running speed increases, show smaller increases in VILR than non-transition runners, i.e. runners that remain with a rearfoot contact pattern (RF).

Methods. Fifty-two male and female runners ran overground at 3.2, 4.1, 5.1 and 6.2?m?s^?1. Ground reaction forces, lower limb sagittal plane knee and ankle kinematics and plantar pressures were recorded. Multi-level linear regression models were used to assess differences between transition and non-transition runners.

Results. Non-transition runners experienced larger speed-induced increases in VILR (48.6?±?2.6?BW?s^?1 per m?s^?1) than transition runners (–1.4?±?7.6?BW?s^?1 per m?s^?1). Transition runners showed higher VILRs and a more flat foot touch down at the same pre-transition speed than non-transition runners.

Conclusion. When running speed increases, some runners transition towards more anterior foot contact patterns. This reduces or even eliminates the speed-induced increase in VILR. This result is especially the case for those RF runners who already have relatively high VILRs and flat foot positioning at slower running speeds.     

A new footwear technology to promote non-heelstrike landing and enhance running performance: Fact or fad?

This study sought to compare the kinetics and kinematics data in a group of habitual shod runners when running in traditional running shoes and newly designed minimalist shoes with lug platform. This novel footwear design claims to simulate barefoot running and reduce energy loss during impact. We compared footstrike angle (FSA), vertical average (VALR) and instantaneous (VILR) loading rates, energy loss and initial vertical stiffness between two shoe conditions. Runners demonstrated a decreased FSA while running in minimalist shoes with lug platform than traditional shoes (P = 0.003; Cohen’s d = 0.918). However, we did not observe a landing pattern transition. VALR and VILR between two footwear conditions showed no significant difference (P = 0.191–0.258; Cohen’s d = 0.304–0.460). Initial vertical stiffness (P = 0.032; Cohen’s d = 0.671) and energy loss (P = 0.044; Cohen’s d = 0.578) were greater when running in minimalist shoes with lug platform. The results show that minimalist shoes with lug platform reduce the FSA but may not lead to a landing pattern switch or lower vertical loading rates. Interestingly, the new shoe design leads to a greater energy loss than traditional running shoes, which could be explained by a higher initial vertical stiffness.     

Metabolic and performance responses of male runners wearing 3 types of footwear: Nike Vaporfly 4%, Saucony Endorphin racing flats,and their own shoes

PurposeWe compared running economy (RE) and 3-km time-trial (TT) variables of runners wearing Nike Vaporfly 4% (VP4), Saucony Endorphin lightweight racing flats (FLAT), and their habitual running (OWN) footwear.MethodsEighteen male recreational runners (age = 33.5 ± 11.9 year (mean ± SD), peak oxygen uptake (VO_2peak) = 55.8 ± 4.4 mL/kg·min) attended 4 sessions approximately 7 days apart. The first session consisted of a VO_2peak test to inform subsequent RE speeds set at 60%, 70%, and 80% of the speed eliciting VO_2peak. In subsequent sessions, treadmill RE and 3-km TTs were assessed in the 3 footwear conditions in a randomized, counterbalanced crossover design.ResultsOxygen consumption (mL/kg·min) was less in VP4 (from 4.3% to 4.4%, p ≤ 0.002) and FLAT (from 2.7% to 3.4%, p ≤ 0.092) vs. OWN across intensities, with a non-significant difference between VP4 and FLAT (1.0%–1.7%, p ≥ 0.292). Findings related to energy cost (W/kg) and energetics cost of transport (J/kg·m) were comparable. VP4 3-km TT performance (11:07.6 ± 0:56.6 mm:ss) was enhanced vs. OWN by 16.6 s (2.4%, p = 0.005) and vs. FLAT by 13.0 s (1.8%, p = 0.032). The 3-km times between OWN and FLAT (0.5%, p = 0.747) were similar. Most runners (n = 11, 61%) ran their fastest TT in VP4.ConclusionOverall, VP4 improved laboratory-based RE measures in male recreational runners at relative speeds compared to OWN, but the RE improvements in VP4 were not significant vs. FLAT. More runners exhibited better treadmill TT performances in VP4 (61%) vs. FLAT (22%) and OWN (17%). The variability in RE (–10.3% to 13.3%) and TT (–4.7% to 9.3%) improvements suggests that responses to different types of shoes are individualized and warrant further investigation.     

Changes in segment coordination variability and the impacts of the lower limb across running mileages in half marathons: Implications for running injuries

BackgroundSegment coordination variability (CV) is a movement pattern associated with running-related injuries. It can also be adversely affected by a prolonged run. However, research on this topic is currently limited. The purpose of this study was to investigate the effects of a prolonged run on segment CV and vertical loading rates during a treadmill half marathon.MethodsFifteen healthy runners ran a half marathon on an instrumental treadmill in a biomechanical laboratory. Synchronized kinematic and kinetic data were collected every 2 km (from 2 km until 20 km), and the data were processed by musculoskeletal modeling. Segment CVs were computed from the angle-angle plots of selected pelvis-thigh, thigh-shank, and shank-rearfoot couplings using a modified vector coding technique. The loading rate of vertical ground reaction force was also calculated. A one-way MANOVA with repeated measures was performed on each of the outcome variables to examine the main effect of running mileage.ResultsSignificant effects of running mileage were found on segment CVs (p ≤ 0.010) but not on loading rate (p = 0.881). Notably, during the early stance phase, the CV of pelvis frontal vs. thigh frontal was significantly increased at 20 km compared with the CV at 8 km (g = 0.59, p = 0.022). The CV of shank transverse vs. rearfoot frontal decreased from 2 km to 8 km (g = 0.30, p = 0.020) but then significantly increased at both 18 km (g = 0.05, p < 0.001) and 20 km (g = 0.36, p < 0.001).ConclusionAt the early stance, runners maintained stable CVs on the sagittal plane, which could explain the unchanged loading rate throughout the half marathon. However, increased CVs on the frontal/transverse plane may be an early sign of fatigue and indicative of possible injury risk. Further studies are necessary for conclusive statements in this regard.     

Reduction in ground reaction force variables with instructed barefoot running

BackgoundBarefoot (BF) running has recently increased in popularity with claims that it is more natural and may result in fewer injuries due to a reduction in impact loading. However, novice BF runners do not necessarily immediately switch to a forefoot strike pattern. This may increase mechanical parameters such as loading rate, which has been associated with certain running-related injuries, specifically, tibial stress fractures, patellofemoral pain, and plantar fasciitis. The purpose of this study was to examine changes in loading parameters between typical shod running and instructed BF running with real-time force feedback.MethodsForty-nine patients seeking treatment for a lower extremity injury ran on a force-sensing treadmill in their typical shod condition and then BF at the same speed. While BF they received verbal instruction and real-time feedback of vertical ground reaction forces.ResultsWhile 92% of subjects (n = 45) demonstrated a rearfoot strike pattern when shod, only 2% (n = 1) did during the instructed BF run. Additionally, while BF 47% (n = 23) eliminated the vertical impact transient in all eight steps analyzed. All loading variables of interest were significantly reduced from the shod to instructed BF condition. These included maximum instantaneous and average vertical loading rates of the ground reaction force (p < 0.0001), stiffness during initial loading (p < 0.0001), and peak medial (p = 0.001) and lateral (p < 0.0001) ground reaction forces and impulses in the vertical (p < 0.0001), medial (p = 0.047), and lateral (p < 0.0001) directions.ConclusionAs impact loading has been associated with certain running-related injuries, instruction and feedback on the proper forefoot strike pattern may help reduce the injury risk associated with transitioning to BF running.     

Predictors of multiple injuries in individual distance runners: A retrospective study of 75,401 entrants in 4 annual races–SAFER XX

BackgroundThere are limited data on factors that predict an increased risk of multiple injuries among distance runners. The objective of this study was to determine risk factors that are predictive of individual runners with a high annual multiple injury risk (MIR).MethodsA retrospective, cross-sectional study at 4 annual (2012–2015) Two Oceans 21.1 km and 56.0 km races in South Africa with 75,401 consenting race entrants. Running-related injury data were collected retrospectively through an online pre-race medical screening questionnaire. The average number of injuries for each runner every year was calculated by taking a runner's race entry history and injury history into account and categorizing entrants into 4 MIR categories (high, intermediate, low, and very low (reference)). Multiple logistic regression modeling (odds ratios) was used to determine whether the following factors were predictive of a high MIR (average > 1 injury/year): demographics, training and racing, chronic-disease history (composite chronic disease score (CCDS)), and history of allergies.ResultsOf all entrants, 9.2% reported at least 1 injury, and 0.4% of entrants were in the high MIR category; the incidence rate was 2.5 injuries per 10 runner-years (95% confidence interval (95%CI): 2.4–2.7). Significant factors predictive of runners in the high MIR category were: running for > 20 years: OR = 2.0 (95%CI: 1.3–3.1; p = 0.0010); a higher CCDS: OR = 2.2 (95%CI: 2.0–2.4; p < 0.0001); and a history of allergies: OR = 2.8 (95%CI: 2.0–3.8; p < 0.0001).ConclusionRunners who have been running recreationally for > 20 years and those with multiple chronic diseases or a history of allergies were at higher risk of multiple running-related injuries. This high-risk group can be targeted for further study and possible injury-prevention interventions.     

Muscle activity and kinematics of forefoot and rearfoot strike runners

BackgroundForefoot strike (FFS) and rearfoot strike (RFS) runners differ in their kinematics, force loading rates, and joint loading patterns, but the timing of their muscle activation is less clear.MethodsForty recreational and highly trained runners ran at four speeds barefoot and shod on a motorized treadmill. “Barefoot” runners wore thin, five-toed socks and shod runners wore neutral running shoes. Subjects were instructed to run comfortably at each speed with no instructions about foot strike patterns.ResultsEleven runners landed with an FFS when barefoot and shod and eleven runners landed with an RFS when barefoot and shod. The 18 remaining runners shifted from an FFS when barefoot to an RFS when shod (shifters). Shod shifters ran with a lower stride frequency and greater stride length than all other runners. All FFS runners landed with more plantarflexed ankles and more vertical lower legs at the beginning of stance compared to RFS runners. FFS runners activated their plantarflexor muscles 11% earlier and 10% longer than RFS runners.ConclusionThis earlier and longer relative activation of the plantarflexors likely enhances the capacity for the passive structures of the foot and ankle to store elastic energy, and may also enhance the performance of the active muscle by increasing the storage of elastic strain energy in the cross-bridges and activated titin.     

Initial foot contact and related kinematics affect impact loading rate in running

This study assessed kinematic differences between different foot strike patterns and their relationship with peak vertical instantaneous loading rate (VILR) of the ground reaction force (GRF). Fifty-two runners ran at 3.2 m · s^?1 while we recorded GRF and lower limb kinematics and determined foot strike pattern: Typical or Atypical rearfoot strike (RFS), midfoot strike (MFS) of forefoot strike (FFS). Typical RFS had longer contact times and a lower leg stiffness than Atypical RFS and MFS. Typical RFS showed a dorsiflexed ankle (7.2 ± 3.5°) and positive foot angle (20.4 ± 4.8°) at initial contact while MFS showed a plantar flexed ankle (?10.4 ± 6.3°) and more horizontal foot (1.6 ± 3.1°). Atypical RFS showed a plantar flexed ankle (?3.1 ± 4.4°) and a small foot angle (7.0 ± 5.1°) at initial contact and had the highest VILR. For the RFS (Typical and Atypical RFS), foot angle at initial contact showed the highest correlation with VILR (r = ?0.68). The observed higher VILR in Atypical RFS could be related to both ankle and foot kinematics and global running style that indicate a limited use of known kinematic impact absorbing “strategies” such as initial ankle dorsiflexion in MFS or initial ankle plantar flexion in Typical RFS.     

A systematic review of running-related musculoskeletal injuries in runners

ObjectiveRunning-related musculoskeletal injuries (RRMIs), especially stemming from overuse, frequently occur in runners. This study aimed to systematically review the literature and determine the incidence and prevalence proportion of RRMIs by anatomic location and specific pathology.MethodsAn electronic database search with no date beginning restrictions was performed in SPORTDiscus, PubMed, and MEDLINE up to June 2020. Prospective studies were used to find the anatomic location and the incidence proportion of each RRMI, whereas retrospective or cross-sectional studies were used to find the prevalence proportion of each RRMI. A separate analysis for ultramarathon runners was performed.ResultsThe overall injury incidence and prevalence were 40.2% ± 18.8% and 44.6% ± 18.4% (mean ± SD), respectively. The knee, ankle, and lower leg accounted for the highest proportion of injury incidence, whereas the knee, lower leg, and foot/toes had the highest proportion of injury prevalence. Achilles tendinopathy (10.3%), medial tibial stress syndrome (9.4%), patellofemoral pain syndrome (6.3%), plantar fasciitis (6.1%), and ankle sprains (5.8%) accounted for the highest proportion of injury incidence, whereas patellofemoral pain syndrome (16.7%), medial tibial stress syndrome (9.1%), plantar fasciitis (7.9%), iliotibial band syndrome (7.9%), and Achilles tendinopathy (6.6%) had the highest proportion of injury prevalence. The ankle (34.5%), knee (28.1%), and lower leg (12.9%) were the 3 most frequently injured sites among ultramarathoners.ConclusionThe injury incidence proportions by anatomic location between ultramarathoners and non-ultramarathoners were not significantly different (p = 0.798). The pathologies with the highest incidence proportion of injuries were anterior compartment tendinopathy (19.4%), patellofemoral pain syndrome (15.8%), and Achilles tendinopathy (13.7%). The interpretation of epidemiological data in RRMIs is limited due to several methodological issues encountered.     

Predictors of multiple injuries in individual distance runners: A retrospective study of 75,401 entrants in 4 annual races–SAFER XX

BackgroundThere are limited data on factors that predict an increased risk of multiple injuries among distance runners. The objective of this study was to determine risk factors that are predictive of individual runners with a high annual multiple injury risk (MIR).MethodsA retrospective, cross-sectional study at 4 annual (2012–2015) Two Oceans 21.1 km and 56.0 km races in South Africa with 75,401 consenting race entrants. Running-related injury data were collected retrospectively through an online pre-race medical screening questionnaire. The average number of injuries for each runner every year was calculated by taking a runner''s race entry history and injury history into account and categorizing entrants into 4 MIR categories (high, intermediate, low, and very low (reference)). Multiple logistic regression modeling (odds ratios) was used to determine whether the following factors were predictive of a high MIR (average > 1 injury/year): demographics, training and racing, chronic-disease history (composite chronic disease score (CCDS)), and history of allergies.ResultsOf all entrants, 9.2% reported at least 1 injury, and 0.4% of entrants were in the high MIR category; the incidence rate was 2.5 injuries per 10 runner-years (95% confidence interval (95%CI): 2.4–2.7). Significant factors predictive of runners in the high MIR category were: running for > 20 years: OR = 2.0 (95%CI: 1.3–3.1; p = 0.0010); a higher CCDS: OR = 2.2 (95%CI: 2.0–2.4; p < 0.0001); and a history of allergies: OR = 2.8 (95%CI: 2.0–3.8; p < 0.0001).ConclusionRunners who have been running recreationally for > 20 years and those with multiple chronic diseases or a history of allergies were at higher risk of multiple running-related injuries. This high-risk group can be targeted for further study and possible injury-prevention interventions.     

One hundred marathons in 100 days: Unique biomechanical signature and the evolution of force characteristics and bone density

BackgroundAn extraordinary long-term running performance may benefit from low dynamic loads and a high load-bearing tolerance. An extraordinary runner (age = 55 years, height = 1.81 m, mass = 92 kg) scheduled a marathon a day for 100 consecutive days. His running biomechanics and bone density were investigated to better understand successful long-term running in the master athlete.MethodsOverground running gait analysis and bone densitometry were conducted before the marathon-a-day challenge and near its completion. The case's running biomechanics were compared pre-challenge to 31 runners who were matched by a similar foot strike pattern.ResultsThe case's peak vertical loading rate (Δx? = –61.9 body weight (BW)/s or –57%), peak vertical ground reaction force (Δx? = –0.38 BW or –15%), and peak braking force (Δx? = –0.118 BW or –31%) were remarkably lower (p < 0.05) than the control group at ～3.3 m/s. The relatively low loading-related magnitudes were attributed to a remarkably high duty factor (0.41) at the evaluated speed. The foot strike angle of the marathoner (29.5°) was greater than that of the control group, affecting the peak vertical loading rate. Muscle powers in the lower extremity were also remarkably low in the case vs. controls: peak power of knee absorption (Δx? = –9.16 watt/kg or –48%) and ankle generation (Δx? = –3.17 watt/kg or –30%). The bone mineral density increased to 1.245 g/cm² (+2.98%) near completion of the challenge, whereas the force characteristics showed no statistically significant change.ConclusionThe remarkable pattern of the high-mileage runner may be useful in developing or evaluating load-shifting strategies in distance running.     

Examining the intrinsic foot muscles’ capacity to modulate plantar flexor gearing and ankle joint contributions to propulsion in vertical jumping

BackgroundDuring human locomotion, a sufficiently stiff foot allows the ankle plantar flexors to generate large propulsive powers. Increasing foot stiffness (e.g., via a carbon plate) increases the ankle's external moment arm in relation to the internal moment arm (i.e., increasing gear ratio), reduces plantar flexor muscles’ shortening velocity, and enhances muscle force production. In contrast, when activation of the foot's intrinsic muscles is impaired, there is a reduction in foot and ankle work and metatarsophalangeal joint stiffness. We speculated that the reduced capacity to actively control metatarsophalangeal joint stiffness may impair the gearing function of the foot at the ankle.MethodsWe used a tibial nerve block to examine the direct effects of the intrinsic foot muscles on ankle joint kinetics, in vivo medial gastrocnemius’ musculotendinous dynamics, and ankle gear ratio on 14 participants during maximal vertical jumping.ResultsUnder the nerve block, the internal ankle plantar flexion moment decreased (p = 0.004) alongside a reduction in external moment arm length (p = 0.021) and ankle joint gear ratio (p = 0.049) when compared to the non-blocked condition. Although medial gastrocnemius muscle–tendon unit and fascicle velocity were not different between conditions, the Achilles tendon was shorter during propulsion in the nerve block condition (p < 0.001).ConclusionIn addition to their known role of regulating the energetic function of the foot, our data indicate that the intrinsic foot muscles also act to optimize ankle joint torque production and leverage during the propulsion phase of vertical jumping.     

Effects of Altered Stride Lengths on Ratings of Perceived Exertion during Running

Abstract

The purpose of this study was to determine the effects of stride length variations on ratings of perceived exertion (RPEs) in experienced recreational runners. Twenty-eight male college students were randomly divided into equal-sized treatment and control groups. The treatment group performed five 15 min altered stride length runs, each separated by a minimum of 48 hr. The five trials involved running with a freely chosen stride length (FCSL) and a FCSL altered by +14%, +7%, ?14%, and ?7%. The control group was utilized to monitor changes in subjects' RPEs as a result of practice effects developed through repeated bouts of treadmill running. Results revealed that the treatment group's local and general RPEs for the over striding runs (+14%, +7%) were significantly greater (p < .01) than RPEs recorded during the FCSL run. Additionally, there was a marginally significant difference (p < .05) in local RPEs between the FCSL run and the extreme understriding run (?14%). Analysis of variance on the control group's RPE data suggests that neither local nor general RPEs changed significantly in repeated FCSL runs across the six-week testing period. The results of this study suggest that experienced recreational runners perceive differences in exertion accompanying changes in stride length.     

Corticospinal activity during a single-leg stance in people with chronic ankle instability

Purpose:The aim of the study was to determine whether corticospinal excitability and inhibition of the tibialis anterior during single-leg standing differs among individuals with chronic ankle instability(CAI),lateral ankle sprain copers,and healthy controls.Methods:Twenty-three participants with CAI,23 lateral ankle sprain copers,and 24 healthy control participants volunteered.Active motor threshold(AMT),normalized motor-evoked potential(MEP),and cortical silent period(CSP)were evaluated by transcranial magnetic stimulation while participants performed a single-leg standing task.Results:Participants with CAI had significantly longer CSP at 100%of AMT and lower normalized MEP at 120%of AMT compared to lateral ankle sprain copers(CSP100%:p=0.003;MEP120%:p=0.044)and controls(CSP100%:p=0.041;MEP120%:p=0.006).Conclusion:This investigation demonstrate altered corticospinal excitability and inhibition of the tibialis anterior during single-leg standing in participants with CAI.Further research is needed to examine the effects of corticospinal maladaptations to motor control of the tibial anterior on postural control performance in those with CAI.     

Metabolic cost of level,uphill, and downhill running in highly cushioned shoes with carbon-fiber plates

BackgroundCompared to conventional racing shoes, Nike Vaporfly 4% running shoes reduce the metabolic cost of level treadmill running by 4%. The reduction is attributed to their lightweight, highly compliant, and resilient midsole foam and a midsole-embedded curved carbon-fiber plate. We investigated whether these shoes also could reduce the metabolic cost of moderate uphill (+3°) and downhill (–3°) grades. We tested the null hypothesis that, compared to conventional racing shoes, highly cushioned shoes with carbon-fiber plates would impart the same ～4% metabolic power (W/kg) savings during uphill and downhill running as they do during level running.MethodsAfter familiarization, 16 competitive male runners performed six 5-min trials (2 shoes × 3 grades) in 2 Nike marathon racing-shoe models (Streak 6 and Vaporfly 4%) on a level, uphill (+3°), and downhill (–3°) treadmill at 13 km/h (3.61 m/s). We measured submaximal oxygen uptake and carbon dioxide production during Minutes 4–5 and calculated metabolic power (W/kg) for each shoe model and grade combination.ResultsCompared to the conventional shoes (Streak 6), the metabolic power in the Vaporfly 4% shoes was 3.83% (level), 2.82% (uphill), and 2.70% (downhill) less (all p < 0.001). The percent of change in metabolic power for uphill running was less compared to level running (p = 0.04; effect size (ES) = 0.561) but was not statistically different between downhill and level running (p = 0.17; ES = 0.356).ConclusionOn a running course with uphill and downhill sections, the metabolic savings and hence performance enhancement provided by Vaporfly 4% shoes would likely be slightly less overall, compared to the savings on a perfectly level race course.     

Lactate Equivalent for Maximal Lactate Steady State Determination in Soccer

ABSTRACT

Purpose: The association between an overlooked classical Lactate Threshold (LT), named “Minimum Lactate Equivalent” (LE_min), with Maximal Lactate Steady State (MLSS) has been recently described with good MLSS prediction results in endurance-trained runners. This study aimed to determine the applicability of LE_min to predict MLSS in lower aerobic-conditioned individuals compared to well-established blood lactate-related thresholds (BLTs). Method: Fifteen soccer players [velocity at MLSS (MLSS_V) 13.2 ± 1.0 km·h^?1; coefficient of variation (CV) 7.6%] conducted a submaximal discontinuous incremental running test to determine BLTs and 3–6 constant velocity running tests to determine MLSS_V. Results: LE_min did not differ from conventional LTs (p > .05) and was 24% lower than MLSS (p < .001; ES: 3.26). Among LTs, LE_min best predicted MLSS_V (r = 0.83; p < .001; SEE = 0.59 km·h^?1). There was no statistical difference between MLSS and estimated MLSS using LE_min prediction formula (p = .99; ES: 0.001). Mean bias and limits of agreement were 0.00 ± 0.58 km·h^?1 and ±1.13 km·h^?1, respectively. LE_min best predicted MLSS_V (r = 0.92; p < .001; SEE = 0.54 km·h^?1) in the pooled data of soccer players and endurance-trained runners of the previous study (n = 28; MLSS_V range 11.2–16.5 km·h^?1; CV 9.8%). Conclusion: Results support LE_min to be one of the best single predictors of MLSS. This study is the sole study providing specific operational regression equations to estimate the impractical gold standard MLSS_V in soccer players by means of a BLT measured during a submaximal single-session test.     

Effect of citrulline on post-exercise rating of perceived exertion,muscle soreness,and blood lactate levels: A systematic review and meta-analysis

BackgroundCitrulline is one of the non-essential amino acids that is thought to improve exercise performance and reduce post-exercise muscle soreness. We conducted a systematic review and meta-analysis to determine the effect of citrulline supplements on the post-exercise rating of perceived exertion (RPE), muscle soreness, and blood lactate levels.MethodsA random effects model was used to calculate the effect sizes due to the high variability in the study design and study populations of the articles included. A systematic search of PubMed, Web of Science, and ClinicalTrials.gov was performed. Eligibility for study inclusion was limited to studies that were randomized controlled trials involving healthy individuals and that investigated the acute effect of citrulline supplements on RPE, muscle soreness, and blood lactate levels. The supplementation time frame was limited to 2 h before exercise. The types and number of participants, types of exercise tests performed, supplementation protocols for L-citrulline or citrulline malate, and primary (RPE and muscle soreness) and secondary (blood lactate level) study outcomes were extracted from the identified studies.ResultsThe analysis included 13 eligible articles including a total of 206 participants. The most frequent dosage used in the studies was 8 g of citrulline malate. Citrulline supplementation significantly reduced RPE (n = 7, p = 0.03) and muscle soreness 24-h and 48-h after post-exercise (n = 7, p = 0.04; n = 6, p = 0.25, respectively). However, citrulline supplementation did not significantly reduce muscle soreness 72-h post-exercise (n = 4, p = 0.62) or lower blood lactate levels (n = 8, p = 0.17).ConclusionCitrulline supplements significantly reduced post-exercise RPE and muscle soreness without affecting blood lactate levels.     

The influence of core affect on cyclo-ergometer endurance performance: Effects on performance outcomes and perceived exertion

BackgroundCore affect is defined as the most general affective construct consciously accessible that is experienced constantly. It can be experienced as free-floating (mood) or related to prototypical emotional episodes. The aim of this study was to examine the influence of pleasant and unpleasant core affect on cyclo-ergometer endurance performance. Specifically, we considered the influence of pleasant and unpleasant core affect on performance outcomes (i.e., time to task completion) and rate of perceived exertion (RPE; Borg Scale, category ratio-10) collected during the task.MethodsThirty-one participants aged 20–28 years were recruited. Core affect was randomly elicited by 2 sets of pleasant and unpleasant pictures chosen from the international affective picture system. Pictures were displayed to participants during a cyclo-ergometer performance in 2 days in a counterbalanced order. RPE was collected every minute to detect volunteers’ exhaustion.ResultsThe study sample was split into 2 groups. Group 1 comprised participants who performed better with pleasant core affect, whereas Group 2 included participants who performed better with unpleasant core affect. Mixed between-within subjects analysis of variance revealed a significant 2 (group) × 2 (condition) × 5 (isotime) interaction (p = 0.002, η_p² = 0.158). Post hoc comparisons showed that participants who obtained better performance with pleasant core affect (pleasant pictures; Group 1) reported lower RPE values at 75% of time to exhaustion in a pleasant core affect condition compared to an unpleasant core affect condition. On the other hand, participants who obtained better performance with unpleasant core affect (unpleasant pictures; Group 2) reported lower RPE values at 75% and 100% of time to exhaustion in an unpleasant core affect condition.ConclusionFindings suggest differential effects of pleasant and unpleasant core affect on performance. Moreover, core affect was found to influence perceived exertion and performance according to participants’ preferences for pleasant or unpleasant core affect.