Effects of Group Running on the Training Intensity Distribution of Collegiate Cross-Country Runners.

ABSTRACT: Farrell III, JW, Dunn, A, Cantrell, GS, Lantis, DJ, Larson, DJ, and Larson, RD. Effects of group running on the training intensity distribution of collegiate cross-country runners. J Strength Cond Res 35(10): 2862-2869, 2021-Collegiate cross-country training is often conducted and prescribed in a group setting. This may result in the application of an inappropriate training stimulus to athletes due to potentially different physiological responses to the same training prescription. The aim of this investigation was to quantify the training intensity distribution (TID) of a collegiate cross-country team and the associated physiological adaptions. Sixteen subjects, 8 male subjects and 8 female subjects, performed a graded exercise test before and after observational period to determine peak oxygen consumption (V̇o2peak), the speed (S@), heart rate (HR@), and oxygen consumption (V̇o2@) associated with 2 and 4 mmol·L-1 of blood lactate. Training intensity distribution was quantified by assessing time spent in 3 intensity zones calculated as zone 1 (low intensity, HR values HR@2 and HR@4). No statistical differences were observed between male subjects and female subjects for percent of training time spent in zones 1, 2, and 3. No significant interactions were observed between sex and time for performance variables. Male subjects and female subjects improved V̇o2peak, S@4, and V̇o2@4 with male subjects also increasing V̇o2@2. No significant differences were observed between male subjects and female subjects when comparing percent changes for variables. Examining individual data showed that 2 female subjects experienced performance decrements and trained proportionally more in zones 2 and 3 compared with the overall group. The TID and performance decrements of the 2 highlighted subjects suggest that conducting training in a group setting may potentially be detrimental for some collegiate runners.

Ankle dorsiflexion asymmetry and the relationship with walking performance in people with multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) is a neurological disease characterized by demyelination disrupting the central nervous system. Persons with MS may exhibit symptomatic strength asymmetry (SA) that impacts motor gait and ankle mobility. The purpose of the present study was to investigate ankle dorsiflexion SA in people with MS and its relationship to functional performance. RESEARCH QUESTION: Is their a difference in dorsiflexion SA in MS participants compared to healthy individuals and does it impact functional performance? METHODS: 13 MS participants (EDSS 3.5 + 1.8) and 13 age matched NON-MS participants underwent maximal isometric (MVC) dynamometry testing for ankle dorsiflexion in both limbs to determine SA. Participants performed three functional tasks of walking performance. RESULTS: There was a significant intra-limb MVC difference in the MS group, and significantly greater isometric SA (p < 0.007) and isokinetic SA (p < 0.04) in the MS group compared to healthy individuals. The MS group exhibited significant correlations between outcomes of functional walking performance with isokinetic but not isometric SA. There was no significant correlation between disability status and functional task performance. SIGNIFICANCE: Ankle dorsiflexion SA is negatively correlated with functional performance in MS participants. MS disability status was not a predictor of functional task performance, and symptom testing may be appropriate to assess walking ability in persons with MS.

Changes in Brain Activity Immediately Post-Exercise Indicate a Role for Central Fatigue in the Volitional Termination of Exercise.

Electroencephalography (EEG) allows for the evaluation of real time changes in brain (electrocortical) activity during exercise. A few studies have examined changes in electrocortical activity using stationary cycling, but the findings have been mixed. Some of these studies have found increases in brain activity following exercise, while others have found decreases in brain activity following exercise. Hence, it is of importance to identify post-exercise changes in brain activity. Sixteen healthy, untrained subjects (8 males; 8 females) participated in the study. All 16 participants performed a graded exercise test (GXT) to volitional exhaustion on an upright cycle ergometer. Continuous EEG recordings were sampled before (PRE) and immediately following (IP) the GXT. Regions of interest were primarily the dorsolateral prefrontal cortex (DLPFC), ventrolateral prefrontal cortex (VLPFC), and left and right motor cortex (MC). In the DLPFC, a frontal asymmetry index was also identified. There was a statistically significant increase in theta power in the DLPFC, VLPFC, and left and right MC from PRE to IP (all p < 0.05). There was also a shift towards right hemisphere asymmetry at the IP time point in the DLPFC (p < 0.05). Finally, there was an increase in alpha power from PRE to IP in the right MC (p < 0.05). EEG could prove to be an important way to measure the effects of central fatigue on brain activity before and immediately following exercise.

Repeatability of the timed 25-foot walk test for individuals with multiple sclerosis.

OBJECTIVE: The purpose of this study was to determine if there is a practice effect present in the timed 25-foot walk in ambulatory individuals with multiple sclerosis. DESIGN: Thirty six people (30 women and 6 men) diagnosed with relapsing remitting multiple sclerosis participated in two testing sessions, one week apart. Each participant performed two sequential trials of the timed 25-foot walk test per session and the walk performance was measured with a laser timing system. RESULTS: We observed improvements in walking speed between the two trials of session one (trial one: 6.42 (0.09) vs. trail two: 5.97 (0.08) seconds, p < 0.001). Within session two, performance remained stable (trial three: 5.71 (0.07) vs. trial four: 5.63 (0.07) seconds, p > 0.05). We also observed a significant improvement in walking speed when averages of the two trials were compared across sessions (session 1: 6.19 (0.09) vs. session 2: 5.67 (0.07) seconds, p < 0.01). CONCLUSIONS: Based on our results, familiarization of the timed 25-foot walk test improves stability of walk performance scores in ambulatory individuals with relapsing remitting multiple sclerosis.

Cerebral blood flow dynamics: Is there more to the story at exercise onset?

A monoexponential model characterizing cerebral blood velocity dynamics at the onset of exercise may mask dynamic responses by the cerebrovasculature countering large fluctuations of middle cerebral artery blood velocity (MCAv) and cerebral perfusion pressure (CPP) oscillations. Therefore, the purpose of this study was to determine whether the use of a monoexponential model attributes initial fluctuations of MCAv at the start of exercise as a time delay (TD). Twenty-three adults (10 women, 23.9 ± 3.3 yrs; 23.7 ± 2.4 kg/m2 ) completed 2 min of rest followed by 3 mins of recumbent cycling at 50 W. MCAv, CPP, and Cerebrovascular Conductance index (CVCi), calculated as CVCi = MCAv/MAP × 100 mmHg, were collected, a lowpass filter (0.2 Hz) was applied, and averaged into 3-second bins. MCAv data were then fit to a monoexponential model [ΔMCAv(t) = Amp(1 - e-(t-TD)/τ )]. TD, tau (τ), and mean response time (MRT = TD + τ) were obtained from the model. Subjects exhibited a TD of 20.2 ± 18.1 s. TD was directly correlated with MCAv nadir (MCAvN ), r = -0.560, p = 0.007, which occurred at similar times (16.5 ± 15.3 vs. 20.2 ± 18.1 s, p = 0.967). Regressions indicated CPP as the strongest predictor of MCAvN ( R a 2 $$ {R}_a^2 $$ = 0.36). Fluctuations in MCAv were masked using a monoexponential model. To adequately understand cerebrovascular mechanisms during the transition from rest to exercise, CPP and CVCi must also be analyzed. A concurrent drop in cerebral perfusion pressure and middle cerebral artery blood velocity at the start of exercise forces the cerebrovasculature to respond to maintain cerebral blood flow. The use of a monoexponential model characterizes this initial phase as a time delay and masks this large important response.

Social Distancing, Psychological Mood and Physical Activity Behavior During COVID-19 in the United States.

Social distancing, during previous epidemics, has been shown to lead to poor mental health outcomes and reduced physical activity. The purpose of the present study was to examine the relationships between self-reported psychological state and physical activity behaviors of individuals under social distancing policies during the COVID-19 pandemic. 199 individuals (29.85 ± 10.22 yrs) in the United States who had been in social distancing for 2-4 weeks participated in this study. Participants answered a questionnaire regarding feelings of loneliness, depression, anxiety, mood state, and physical activity. 66.8% of participants had depressive symptoms and 72.8% had symptoms of anxiety. Loneliness was correlated with depression (r = 0.66), trait anxiety (r = 0.36), fatigue (r = 0.38), confusion (r = 0.39), and total mood disturbance (TMD; r = 0.62). Participation in total physical activity was negatively associated with depressive symptoms (r = -0.16) and TMD (r = -0.16). State anxiety was positively associated with participation in total physical activity (r = 0.22). In addition, a binomial logistic regression was performed to predict participation in sufficient physical activity. The model explained 45% of the variance in physical activity participation and correctly categorized 77% of cases. Individuals with higher vigor scores had an increased likelihood of participating in sufficient physical activity. Loneliness was associated with negative psychological mood state. Individuals with higher feelings of loneliness, depressive symptoms, trait anxiety, and negative mood state were observed to spend less time engaged in physical activity. Higher state anxiety was positively associated with engagement in physical activity.

Relationship between soleus H-reflex asymmetry and postural control in multiple sclerosis.

BACKGROUND: Impaired postural control is a common symptom in people with multiple sclerosis. Multiple sclerosis frequently presents with asymmetric motor involvement. One measurement yet to be evaluated for asymmetry in people with multiple sclerosis is the soleus Hoffmann reflex. PURPOSE: To measure the soleus Hoffmann reflex between limbs and correlate reflex asymmetry with postural control. MATERIAL AND METHODS: 16 participants completed four sessions of Hoffmann reflex testing and one session of balance testing. RESULTS: Multiple sclerosis participants had significantly greater reflex asymmetry (p = 0.01). The multiple sclerosis group had a significantly lower overall sensory organization testing composite score (p < 0.05), indicating sensory interpretation conflict that resulted in greater postural instability. Multiple sclerosis participants produced a significantly shorter endpoint and maximum excursion (p < 0.01) during limits of stability testing. Hoffmann reflex asymmetry was negatively related to forward endpoint excursion (p < 0.05), maximum excursion (p ≤ 0.01). CONCLUSIONS: Multiple sclerosis participants had greater soleus Hoffmann reflex asymmetry, which appears to significantly influence forward postural control.Implications for rehabilitationSoleus Hoffmann reflex asymmetry appears to influence postural stability.The soleus Hoffmann reflex is capable of adapting to different modes of exercise; therefore, to reduce H-reflex asymmetry it is recommended to individualize physical rehabilitative programming.Assessing the soleus Hoffmann reflex in people with multiple sclerosis during health screenings could be of use to clinical and rehabilitative practitioners.

An evaluation of the reliability of the foot-tapping test in a healthy sample.

The foot-tapping test (FTT) can be used to assess upper motor neuron dysfunction in clinical populations. However, relatively little is known regarding the reliability or normative values of the FTT in either healthy or clinical populations. Although several different FTT methods have been used, no study to date has demonstrated the reliability or validity of FTT by comparing it across several different counting methods in healthy persons. This unfortunately limits its usefulness in medicine and research. OBJECTIVE: This study sought to examine the reliability and validity of the FTT in healthy individuals to determine its usefulness and to make recommendations for its implementation in clinical populations. Furthermore, the concurrent validity and reliability of using a force plate as an objective measure of foot-taps was considered. DESIGN: Thirty-eight healthy individuals had their foot-tapping assessed using Live, Force Plate, and Video Counting methods over four separate visits. METHODS: Participants were seated as per previous FTT recommendations and asked to tap their foot in 10-second intervals while the number of taps was counted via Live, Video, and Force Plate counters. This was done with both legs, with shoes ON and OFF, and repeated over four separate visits. RESULTS: Despite significant differences between repeat trials for Force Plate and Video Counts (∼2 foot-taps, p < 0.01), test-retest reliability was high for all three methods (Pearson's R > 0.90). Dominant foot trials were higher (∼2 foot-taps, p < 0.05) than Non-dominant for all three counts. When performed with shoes ON, counts were higher (∼2 foot-taps, p < 0.05) than OFF for the Live and Force Plate counts. Reliability between visits was high (ICC > 0.80) and only the Video count was significantly lower for Visit 1 (p < 0.01). CONCLUSIONS: Given findings, the authors suggest using a Force Plate counting method and have compiled a list of suggestions for future implementation of the FTT.

Perceptual responses: Clinical versus practical blood flow restriction resistance exercise.

The purpose of the current investigation was to compare the acute perceptual responses during low-load resistance exercise (RE) with clinical blood flow restriction (cBFR-RE) and practical blood flow restriction (pBFR-RE), and during conventional low- (LL-RE) and high-load resistance exercise (HL-RE), to determine if these responses differed between young males and females. Twenty-nine participants (14 males: 23.6±2.7years, 25.3±3.1kg/m2 and 15 females: 20.3±1.6years, 23.4±1.9kg/m2) completed the following exercise conditions in a randomized design: 1) cBFR-RE, 2) pBFR-RE, 3) HL-RE, and 4) LL-RE. Low-load conditions consisted of 30-15-15-15 repetitions of two-leg press (LP) and knee extension (KE) exercises with 30% one-repetition maximum (1-RM), and HL-RE consisted of 3 sets of 10 repetitions at 80% 1-RM, all with 60s rest intervals. Ratings of perceived exertion (RPE) and discomfort were assessed before exercise and immediately following each set. RPE was significantly higher in HL-RE compared to all low-load conditions for both exercises after each set (all p<0.05). cBFR-RE resulted in significantly greater RPE than pBFR-RE and LL-RE for both exercises for sets 1-4 for LP and sets 2-3 for KE (all p<0.05). Levels of discomfort were similar between cBFR-RE and HL-RE, which tended to be significantly higher than pBFR-RE and LL-RE (p<0.05). Men reported significantly greater RPE than women following sets 2-4 during KE with cBFR-RE and sets 2 and 3 during KE for HL-RE (all p<0.05). Males also reported significantly greater discomfort than women following sets 2-4 for KE LL-RE (p<0.05). Altogether, these data suggest that pBFR-RE may provide a more favorable BFR condition based on perceptual responses and that perceptual responses may differ between sexes across varying resistance exercise conditions.

Cerebrovascular responses to graded exercise in young healthy males and females.

Although systemic sex-specific differences in cardiovascular responses to exercise are well established, the comparison of sex-specific cerebrovascular responses to exercise has gone under-investigated especially, during high intensity exercise. Therefore, our purpose was to compare cerebrovascular responses in males and females throughout a graded exercise test (GXT). Twenty-six participants (13 Females and 13 Males, 24 ± 4 yrs.) completed a GXT on a recumbent cycle ergometer consisting of 3-min stages. Each sex completed 50W, 75W, 100W stages. Thereafter, power output increased 30W/stage for females and 40W/stage for males until participants were unable to maintain 60-80 RPM. The final stage completed by the participant was considered maximum workload(Wmax ). Respiratory gases (End-tidal CO2 , EtCO2 ), middle cerebral artery blood velocity (MCAv), heart rate (HR), non-invasive mean arterial pressure (MAP), cardiac output (CO), and stroke volume (SV) were continuously recorded on a breath-by-breath or beat-by-beat basis. Cerebral perfusion pressure, CPP = MAP (0. 7,355 distance from heart-level to doppler probe) and cerebral vascular conductance index, CVCi = MCAv/CPP 100mmHg were calculated. The change from baseline (Δ) in MCAv was similar between the sexes during the GXT (p = .091, ωp2  = 0.05). However, ΔCPP (p < .001, ωp2  = 0.25) was greater in males at intensities ≥ 80% Wmax and ΔCVCi (p = .005, ωp2  = 0.15) was greater in females at 100% Wmax . Δ End-tidal CO2 (ΔEtCO2 ) was not different between the sexes during exercise (p = .606, ωp2  = -0.03). These data suggest there are sex-specific differences in cerebrovascular control, and these differences may only be identifiable at high and severe intensity exercise.

Evaluation of Power Production Asymmetry during Cycling in Persons with Multiple Sclerosis.

Lower limb asymmetries have been observed in persons with multiple sclerosis (PwMS), and have been associated with mobility impairment. An incremental cycling test was performed on a cycle ergometer to determine peak power output (PPO) and peak oxygen consumption (VO2peak). Then, participants cycled at 50%, 60%, and 70% of their PPO to assess the contribution of each lower limb to power production. Two-way repeated measures ANOVA was used to detect group × intensity differences in power production asymmetry. Eight PwMS and six healthy individuals (Non-MS) completed the study. No statistically significant (p > 0.05) group × intensity interactions or main effects were present when examining between-limb differences in power production. The current data do not indicate a statistically significant difference in power production asymmetry between groups and exercise intensities. Previous research has established a 10% difference between contralateral limbs as a threshold for asymmetry. The average asymmetry in power production in PwMS exceeded the 10% threshold at all measured outputs, suggesting the presence of asymmetry in power production.

Lower-limb performance disparities: implications for exercise prescription in multiple sclerosis.

The purpose of this study was to examine unilateral lower-limb exercise tolerance during fixed-load cycling to quantify performance disparities of the legs. Eight individuals with relapsing-remitting multiple sclerosis (MS) and seven controls performed submaximal single-leg cycling. Individuals with MS performed significantly more work with the stronger leg than the weaker leg (stronger leg: 6.4 +/- 1.7 kJ, weaker leg: 4.7 +/- 2.5 kJ, p = 0.02). The control group displayed no statistical differences between limbs (p = 0.36). These results highlight a need for individualized exercise testing when prescribing training programs for those with MS.

Bilateral differences in lower-limb performance in individuals with multiple sclerosis.

Bilateral differences in lower-limb strength in people with multiple sclerosis (MS) have been clinically observed. The objectives of this study were to quantify bilateral differences in lower-limb performance and metabolism during exercise. Eight ambulatory individuals with mild MS with an Expanded Disability Status Scale score of 2.6 +/- 1.6 and seven non-MS controls completed bilateral assessments of muscle strength and incremental cycling. Individuals with MS had significant (p < 0.05) between-leg differences in leg strength (strong leg: 43.3 +/- 12.7 kg vs weak leg: 37.7 +/- 15.2 kg), peak oxygen uptake (strong leg: 13.7 +/- 3.2 mL/kg/min vs weak leg: 10.6 +/- 3.0 mL/kg/min), and peak workload (strong leg: 73.4 +/- 22.3 W vs weak leg: 56.3 +/- 26.2 W). No between-leg differences were found in controls (p > 0.05). As anticipated, individuals with MS exhibited significantly greater asymmetry for strength, oxygen uptake, and workload than controls (p < 0.05). The differences between legs varied from 2% to 30% for maximal strength and 4% to 66% for cycling workload in the MS group and 4% to 24% and 0% to 8% for the control group, respectively. Preliminary evidence suggests that the magnitude of differences may be related to limitations in aerobic function.