Medicine & Science in Sports & Exercise

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Fatigue-related Feedback from Calf Muscles Impairs Knee Extensor Voluntary Activation

imageIntroduction
Fatigue-related group III/IV muscle afferent firing from agonist, antagonist or distal muscles impairs the ability to drive the elbow flexors maximally, that is, reduces voluntary activation. In the lower limb, the effect of feedback from distal muscles on the proximal knee extensors is unknown. Here, we test whether maintained group III/IV afferent feedback from the plantarflexor muscles reduces voluntary activation of the knee extensors.
Methods
On 2 d, voluntary activation of the knee extensors during maximal voluntary contractions (MVCs) was assessed in 12 participants before and after a 3-min fatiguing task of the plantarflexors. On 1 d, an inflatable cuff around the calf occluded blood flow for 2 min immediately postexercise (cuff day). The other day had no occlusion (no-cuff day). Supramaximal stimulation of the femoral nerve elicited superimposed twitches during MVC of the knee extensors and resting twitches 2 to 3 s after relaxation. Pain (0–10 point scale) was reported throughout.
Results
In the 2 min after the 3-min fatiguing plantarflexor task, voluntary activation was 5.3% (SD, 7%) lower on the cuff day than on the no-cuff day (P = 0.045), and MVC force was reduced by 13% (SD, 16%) (P = 0.021). The resting twitch was similar on both days (P = 0.98). Pain rated 4.9 points higher with the cuff inflated (P = 0.001).
Conclusions
Maintained group III/IV afferent feedback from the fatigued plantarflexor muscles reduced maximal force and voluntary activation of the unfatigued knee extensors, suggesting that afferents from the calf act centrally to inhibit the ability to drive the motoneurones of the knee extensors.

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https://journals.lww.com/acsm-msse/Fulltext/2020/10000/Fatigue_related_Feedback_from_Calf_Muscles_Impairs.9.aspx

Domain-Specific Physical Activity, Pain Interference, and Muscle Pain after Activity

imagePurpose
Using the Melbourne Collaborative Cohort Study, we examined the associations of occupation, household, transport, and leisure physical activity with pain interference with normal work and muscle pain after activity.
Methods
This cross-sectional analysis included 7655 working and 11,766 nonworking participants. Physical activity was assessed using the long-form International Physical Activity Questionnaire. Pain interference was assessed with the Short-Form 12-Item Health Survey version 2.0, and muscle pain after activity was assessed using the 12-item Somatic and Psychological Health Report. Ordered logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI), and restricted cubic splines were used to graphically represent the shape of associations.
Results
All physical activity domain–pain outcome associations were nonlinear. Compared with participants who reported the lowest level of activity, participants who reported the median level of transport physical activity (10 MET·h·wk−1) reported less pain interference (workers: OR, 0.86 [95% CI, 0.77–0.97]; nonworkers: OR, 0.88 [95% CI, 0.79–0.97]) and muscle pain after activity (workers: OR, 0.81 [95% CI, 0.70–0.95]; nonworkers: OR, 0.86 [95% CI, 0.77–0.95]). Higher levels of leisure time activity (20 MET·h·wk−1) were associated with less pain interference in nonworkers (OR, 0.87; 95% CI, 0.77–0.98) and muscle pain after activity in workers (OR, 0.67; 95% CI, 0.56–0.80). Workers who reported the median level of household activity (16 MET·h·wk−1) had increased pain interference (OR, 1.19; 95% CI, 1.07–1.32) and muscle pain after activity (OR, 1.23; 95% CI, 1.06–1.42) than did those who reported the least household activity.
Conclusions
Associations between domain-specific physical activity and pain outcomes were not uniform. Within the transport and leisure domains, physical activity was inversely associated with pain-related outcomes, whereas household physical activity was positively associated with pain scores within the working sample.

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https://journals.lww.com/acsm-msse/Fulltext/2020/10000/Domain_Specific_Physical_Activity,_Pain.10.aspx

Physical Inactivity among Ghanaians in Ghana and Ghanaian Migrants in Europe

imagePurpose
There is a paucity of data on physical activity (PA) among migrants from sub-Saharan Africa, yet physical inactivity is a key risk factor for noncommunicable diseases. We examined the levels of physical inactivity and its determinants among Ghanaians in different geographical locations.
Methods
We used the Research on Obesity and Diabetes among African Migrants data of Ghanaian adults (n = 4760) age 25–70 yr in rural and urban Ghana and three European cities (Amsterdam, London, and Berlin). Using total physical activity metabolic equivalent of task, physical inactivity was defined as total physical activity metabolic equivalent of task minutes per week less than 600. Logistic regression was used to examine the differences in the levels and the determinants of physical inactivity across sites.
Results
Physical inactivity was higher among Ghanaian migrants (14.6% in Amsterdam, 24.1% in Berlin, and 36.6% in London) and urban Ghanaians (29.0%) compared with rural Ghanaians (11.2%). After adjustment for covariates (age, sex, education, health status, smoking status, body mass index, and social network) using rural Ghanaians as the comparator group, the odds ratios for physical inactivity in men ranged from 3.67 (95% confidence interval, 2.19–6.16) in urban Ghanaians to 10.37 (5.96–18.02) in London Ghanaians, and from 3.27 (2.46–4.35) in urban Ghanaians to 4.41 (3.12–6.22) in London Ghanaians in women. Migrants in London and Berlin had higher odds of physical inactivity compared with Amsterdam. Increased age, university education, and overweight/obesity were positively associated with physical inactivity, whereas social support was inversely associated with physical inactivity with variability across sites.
Conclusions
Findings indicate high prevalence of physical inactivity among Ghanaians in all sites, particularly among Ghanaians in Europe. Hence, there is the need to take local context into account to improve PA.

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https://journals.lww.com/acsm-msse/Fulltext/2020/10000/Physical_Inactivity_among_Ghanaians_in_Ghana_and.11.aspx

Muscle Metabolism and Fatigue during Simulated Ice Hockey Match-Play in Elite Players

imagePurpose
The present study investigated muscle metabolism and fatigue during simulated elite male ice hockey match-play.
Methods
Thirty U20 male national team players completed an experimental game comprising three periods of 8 × 1-min shifts separated by 2-min recovery intervals. Two vastus lateralis biopsies were obtained either during the game (n = 7) or pregame and postgame (n = 6). Venous blood samples were drawn pregame and at the end of the first and last periods (n = 14). Activity pattern and physiological responses were continuously monitored using local positioning system and heart rate recordings. Further, repeated-sprint ability was tested pregame and after each period.
Results
Total distance covered was 5980 ± 199 m with almost half the distance covered at high skating speeds (>17 km·h−1). Average and peak on-ice heart rate was 84% ± 2% and 97% ± 2% of maximum heart rate, respectively. Muscle lactate increased (P ≤ 0.05) more than fivefold and threefold, whereas muscle pH decreased (P ≤ 0.05) from 7.31 ± 0.04 pregame to 6.99 ± 0.07 and 7.13 ± 0.11 during the first and last periods, respectively. Muscle glycogen decreased by 53% postgame (P ≤ 0.05) with ~65% of fast- and slow-twitch fibers depleted of glycogen. Blood lactate increased sixfold (P ≤ 0.05), whereas plasma free fatty acid levels increased 1.5-fold and threefold (P ≤ 0.05) after the first and last periods. Repeated-sprint ability was impaired (~3%; P ≤ 0.05) postgame concomitant with a ~10% decrease in the number of accelerations and decelerations during the second and last periods (P ≤ 0.05).
Conclusions
Our findings demonstrate that a simulated ice hockey match-play scenario encompasses a high on-ice heart rate response and glycolytic loading resulting in a marked degradation of muscle glycogen, particularly in specific sub-groups of fibers. This may be of importance both for fatigue in the final stages of a game and for subsequent recovery.

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https://journals.lww.com/acsm-msse/Fulltext/2020/10000/Muscle_Metabolism_and_Fatigue_during_Simulated_Ice.12.aspx

Effect of Strength Training on Glycemic Control and Adiponectin in Diabetic Children

imagePurpose
This study aimed to examine the effect of isolated supervised progressive resistance training with duration of more than 32 wk on muscle strength, metabolic control and adiponectin.
Method
Twenty-one children with type 1 diabetes mellitus were separated into an intervention group (IG) (n = 11 age 11.0 ± 0.8) and a control group (CG) (n = 10 age 11.30 ± 0.7) without training to control for the effect of progressive resistance training on muscle strength, hemoglobin (HbA)1C and adiponectin. All parameters were assessed before and after a period of 32 wk. No attempt was made to change diet and the daily behaviors during the study in both groups.
Results
After a period of 32 wk, upper and lower limb strength increased significantly (P < 0.05) in the IG, whereas no changes occurred in the CG. In the IG, HbA1C decreased significantly after 32 wk but not after 17 wk (P < 0.00), whereas HbA1C increased in the CG (P < 0.007). Adiponectin increased significantly (P < 0.000) only in the IG. Self-monitored blood glucose levels, measured before and after each session, showed a significant reduction (P < 0.00) of 26.5% ± 4.4% after each session. Effect size (ES) for the strength training on limb strength was medium (d = 0.464 to d = 0.661), the ES for strength training on HbA1C (d = −1.292) and the ES for strength training on adiponectin (d = 1.34) was large. There was no hypoglycemia as the result of training.
Conclusions
An isolated supervised progressive resistance training two times a week in children with type 1 diabetes mellitus must last at least 32 wk to get a significant decrease in blood glucose level HbA1C. In addition, exercise-induced increase in adiponectin improves insulin sensitivity.

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https://journals.lww.com/acsm-msse/Fulltext/2020/10000/Effect_of_Strength_Training_on_Glycemic_Control.13.aspx

Associations between Range of Motion and Tissue Stiffness in Young and Older People

imagePurpose
The purpose of this study was to investigate differences in the associations between passive ankle dorsiflexion range of motion (ROM) and stiffness of the triceps surae, sciatic nerve, and deep fascia located in the posterior leg between young and older people.
Methods
Twenty young and twenty older males were recruited and were placed in a prone position with their hip and knee fully extended. Passive ankle dorsiflexion ROM was determined based on the onset of pain during passive dorsiflexion at 1°·s−1 using an isokinetic dynamometer. Shear wave speeds (as a stiffness index) of the triceps surae, the sciatic nerve, and the deep fascia in the posterior leg were evaluated by ultrasound shear wave elastography.
Results
The shear wave speeds of the medial and lateral gastrocnemius measured at 15° dorsiflexion correlated negatively with passive ROM in young but not in older participants. The shear wave speed of the sciatic nerve measured at 15° dorsiflexion correlated negatively with passive ROM only in older participants. No association was observed between passive ROM and shear wave speed of the deep fascia in the posterior leg. For data measured at maximal dorsiflexion angle (as an index of stretch tolerance), shear wave speeds of the triceps surae and passive joint torque correlated positively with passive ROM in both groups.
Conclusion
These results suggest that the tissues limiting passive ankle dorsiflexion ROM are muscle and nerve for young and older people, respectively, whereas stretch tolerance influences passive ROM for both groups. This implies that the relative contribution of nonmuscular tissues to joint flexibility become stronger than that of muscles with age.

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https://journals.lww.com/acsm-msse/Fulltext/2020/10000/Associations_between_Range_of_Motion_and_Tissue.14.aspx

Plantar Flexor Function in Adults with and without Prader–Willi Syndrome

imagePurpose
Prader–Willi Syndrome (PWS) is a form of congenital obesity characterized by excessive body fat, hypotonia, muscle weakness, and physical/cognitive disability. However, the sources of muscle dysfunction and their contribution to mobility are unclear. The purposes of this study were to 1) compare plantar flexor function between adults with and without PWS; and 2) to examine the relationship between plantar flexor function and gait speed in adults with PWS.
Methods
Participants included 10 adults with PWS, 10 adults without PWS and with obesity, and 10 adults without PWS and without obesity (matched on age and sex). Plantar flexor function was assessed using isokinetic dynamometry (peak torque [PT], early/late rate of torque development [RTD]), Hoffman reflex (H/M ratio), ultrasound imaging (cross-sectional area [CSA], echo intensity, pennation angle, and fascicle length), and peak propulsive force and plantar flexor moment during gait. Outcomes were compared between groups using one-way MANOVA. Associations between plantar flexor outcomes and gait speed were assessed using Pearson correlation in the PWS group.
Results
Adults with PWS had lower absolute and normalized early RTD, and lower H/M ratio than controls with and without obesity; lower absolute PT and late RTD than controls with obesity (all P < 0.05). Cross-sectional area, propulsive force, and plantarflexor moment were lower, and echo intensity was higher, in adults with PWS compared with controls without obesity (all P < 0.05). Greater absolute PT (r = 0.64), absolute early RTD (r = 0.62), absolute late RTD (r = 0.64), gastrocnemii CSA (r = 0.55), and propulsive force (r = 0.58) were associated with faster gait speed (all P < 0.05).
Conclusions
Adults with PWS have impaired plantar flexor function likely attributable to reduced neuromuscular function and altered muscle morphology, which are associated with slower gait speeds.

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https://journals.lww.com/acsm-msse/Fulltext/2020/10000/Plantar_Flexor_Function_in_Adults_with_and_without.15.aspx

Head Impact Telemetry System’s Video-based Impact Detection and Location Accuracy

imagePurpose
This study aimed to quantify the Head Impact Telemetry (HIT) System’s impact detection and location measurement accuracy using an impact biomechanics data set paired with video of high school football special teams plays.
Methods
The head impact biomechanics data set and video were collected from 22 high school football players, wearing HIT System instrumented helmets, competing in 218 special teams plays over a single high school football season. We used two separate video analysis approaches. To quantify the impact detection accuracy, we evaluated the video for head impacts independently of the impact data collection triggers collected by the HIT System. Video-observed impacts matched to valid and invalid head impacts by the HIT System algorithm were categorized as true positives, false positives, false negatives, and true negatives. To quantify impact location accuracy, we analyzed video-synchronized head impacts for impact location independent of the HIT System’s impact location measurement and quantified the estimated percent agreement of impact location between the HIT System recorded impact location and the impact location observed on video.
Results
The HIT System’s impact-filtering algorithm had 69% sensitivity, 72% specificity, and 70% accuracy in categorizing true and non–head impact data collection triggers. The HIT System agreed with video-observed impact locations on 64% of the 129 impacts we analyzed (unweighted k = 0.43, 95% confidence interval = 0.31–0.54).
Conclusion
This work provides data on the HIT System’s impact detection and location accuracy during high school football special teams plays using game video analysis that has not been previously published. Based on our data, we believe that the HIT System is useful for estimating population-based impact location distributions for special teams plays.

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https://journals.lww.com/acsm-msse/Fulltext/2020/10000/Head_Impact_Telemetry_System_s_Video_based_Impact.16.aspx

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