Quantifying knee mechanics during balance training exercises

Patellofemoral pain (PFP) is common among runners and those recovering from anterior cruciate ligament reconstruction. Training programs designed to prevent or treat injuries often include balance training, although balance interventions have been reported to coincide with more knee injuries. Knowledge of the effect of balance exercises on knee mechanics may be useful when designing training programs. High knee abduction moment has been implicated in the development of PFP, and imbalance between vastus lateralis (VL) and vastus medialis oblique (VMO) may contribute to patellofemoral stress. The purpose was to quantify knee abduction moment and vasti muscle activity during balance exercises. Muscle activity of VMO and VL, three-dimensional lower-extremity kinematics, and ground reaction forces of healthy recreational athletes (12M, 13F) were recorded during five exercises. Peak knee abduction moment, ratio of VMO:VL activity, and delay in onset of VMO relative to VL were quantified for each exercise. The influence of sex and exercise on each variable was determined using a mixed-model ANOVA. All analyses indicated a significant main effect of exercise, p < 0.05. Follow-up comparisons showed low peak knee abduction moment and high VMO:VL ratio for the task with anterior-posterior motion. Delay of VMO relative to VL was similar among balance board tasks.     

Muscle coordination patterns in regulation of medial gastrocnemius activation during walking

The ankle plantar flexion in the late stance phase is referred to as the ankle push-off. When the ankle push-off force is enhanced, compensatory adjustments occur in the adjacent phases. The muscle control that achieves these compensatory movements remains unknown, although they are expected to be coordinately regulated across multiple muscles and phases. Muscle synergy is used as a quantification technique for muscle coordination, and this analysis enables the comparison of synchronized activity between multiple muscles. Therefore, this study aimed to elucidate the tuning of muscle synergies in muscle activation adjustment of push-off. It is hypothesized that muscle activation adjustment of push-off is performed in the muscle synergy related to ankle push-off and in the muscle synergy that activates during the adjacent push-off phase. Eleven healthy men participated, and participants manipulated the activity of the medial gastrocnemius during walking through visual feedback. Two conditions were compared as experimental conditions: increasing the muscle activity to 1.6 times that during normal walking (High) and matching it with that during normal walking (Normal). Twelve muscle activities in the trunk and lower limb and kinematic data were recorded. Muscle synergies were extracted by the non-negative matrix factorization. No significant difference was observed in the number of synergies (High: 3.5 ± 0.8, Normal: 3.7 ± 0.9, p = 0.21) and muscle synergy activation timing and duration between the High and Normal conditions (p > 0.27). However, significant differences were observed in the peak muscle activity during the late stance phase of the rectus femoris (RF), biceps femoris (BF) between conditions (RF at High: 0.32 ± 0.21, RF at Normal: 0.45 ± 0.17, p = 0.02; BF at High: 0.16 ± 0.01, BF at Normal: 0.08 ± 0.06 p = 0.02). Although the quantification of force exertion has not been conducted, the modulation of RF and BF activation could have occurred due to the attempts to help knee flexion. Muscle synergies during normal walking are therefore maintained, and slight adjustments in the amplitude of muscle activity occurred for each muscle.     

Use of self-organizing maps to study sex- and speed-dependent changes in running biomechanics

BackgroundUp to 79% of runners get injured every year, with higher rates of injuries occurring in females than males. A self-organizing map (SOM) is a type of artificial neural network that can be used to inspect large datasets and study coordination patterns. The purpose of this study was to use an SOM to study the effects of sex and speed on biomechanical coordination patterns.MethodThirty-two healthy runners ran on an instrumented treadmill at their long slow distance speed (LSD) and at speed 30% faster (LSD + 30%). Vertical ground reaction force (vGRF), vertical tibial acceleration, step parameters, electromyograms (EMG) of six lower limb muscles, and joint angles were collected across speeds. Rate of loading (ROL), tibial impact shock (TIS), coupling angle variability (CAV) and movement pattern proportions for hip/knee sagittal and hip frontal / knee sagittal plane couplings, peak EMG, step length, step rate, and knee and ankle joint angle at initial contact were used as an input for the SOM (37 variables).ResultsThe analysis identified four clusters (i.e., running patterns). While males and females showed similar distribution across clusters at LSD (p = .36) and at LSD + 30% (p = .51), females did exhibit a significant (p = .03) shift between clusters as the speed increased from LSD to LSD + 30% whereas males did not (p = .17). The shift was associated with an increase in TIS, ROL, step length, step rate, vastus lateralis EMG, hip flexion/knee extension movement pattern proportion, and a decrease in ST EMG and CAV_IC for hip sagittal/knee sagittal coupling.ConclusionAs running speed increased there was a significant change in the coordination pattern in females, which was characterized by increases in several variables that are purported risk factors for running related injuries.     

Effect of taping and its conditions on electromyographic responses of knee extensor muscles

IntroductionThe present study investigated the effect of stretchable characteristics of elastic therapeutic tape and its elongation on surface electromyography (EMG) of knee extensor muscles during knee extension movements.MethodsNine healthy men performed knee extension movement with the application of normal elastic tape or highly stretchable tape and without the tapes (control). Tapes were applied on the anterior thigh to cross the knee joint with no elongation and elongation of 50 and 75% of the maximum stretchability. Surface EMG was recorded from the vastus lateralis (VL) muscle and proximal (RFp) and distal (RFd) sites of the rectus femoris muscle.ResultsUnder the no-elongation conditions, decreases in the surface EMG amplitude of the VL and RFd muscles were observed with normal tape during the isometric contraction phase and with highly stretchable tape during isometric and eccentric contraction phases, compared with the control (p < 0.05). There were no significant differences in surface EMG among the different elongation conditions in any muscles (p > 0.05).DiscussionThese results suggest that the stretchable characteristics of tapes change the effect of elastic tape application on neuromuscular activation of the applied muscles and these effects are not dependent on the elongation of the tape.     

The relationship between hip,knee and ankle muscle mechanical characteristics and gait transition speed

The purpose of the present study was to explore the relationship between mechanical characteristics of hip, knee and ankle extensor and flexor muscle groups and gait transition speed. The sample included 29 physically active male adults homogenized regarding their anthropometric dimensions. Isokinetic and isometric leg muscle mechanical characteristics were assessed by an isokinetic dynamometer, while individual walk-to-run (WRT) and run-to-walk transition speeds (RWT) were determined using the standard increment protocol. The relationship between transition speeds and mechanical variables scaled to body size was determined using Pearson correlation and stepwise linear regression. The highest correlations were found for isokinetic power of ankle dorsal flexors and WRT (r = .468, p < .01) and the power of hip extensors and RWT (r = .442, p < .05). These variables were also the best predictors of WRT and RWT revealing approximately 20% of explained variance. Under the isometric conditions, the maximal force and rate of force development of hip flexors and ankle plantar flexors were moderately related with WRT and RWT (ranged from r = .340 to .427). The only knee muscle mechanical variable that correlated with WRT was low velocity knee flexor torque (r = .366, p < .05). The results generally suggest that the muscle mechanical properties, such as the power of ankle dorsal flexors and hip extensors, influence values of WRT and RWT.     

Real-time kinematic biofeedback improves scapulothoracic control and performance during scapular-focused exercises: A single-blind randomized controlled laboratory study

Emerging evidence suggests that scapular-focused therapeutic exercises hold promise for shoulder dynamic stability retraining. While recent findings show that therapeutic exercises can alter scapular neuromuscular function measured with muscle electromyography, no study has yet addressed the effects of kinematic biofeedback for improving scapulothoracic control and performance. The aim of this study was to assess the effectiveness of kinematic biofeedback on motor relearning transfer during shoulder flexion and a daily activity, on the quality of scapular-focused exercise performance, and on execution time. Thirty healthy young adults were randomly distributed into two groups. Skin mounted electromagnetic sensors were used to collect kinematic data of the thorax, scapula and humerus while subjects performed a shoulder flexion and a daily activity, prior to and after scapular-focused exercises. For both groups, the exercise execution error and the execution time determined the scapulothoracic control and performance. Significant statistical differences were found in the exercise execution error results within the experimental group (z = 5.313; p = 0.037) and between groups (u = 37.00; p = 0.001; u = 64.00; p = 0.024). This study’s results demonstrate that real-time kinematic biofeedback improves scapulothoracic control and performance during scapular-focused exercise execution.     

Smaller muscle mass is associated with increase in EMG–EMG coherence of the leg muscle during unipedal stance in elderly adults

Age-induced decline in the ability to perform daily activities is associated with a deterioration of physical parameters. Changes occur in neuromuscular system with age; however, the relationship between these changes and physical parameters has not been fully elucidated. Therefore, in this study, we aimed to determine the relationship between neuromuscular system evaluated using a coherence analysis of the leg muscles and physical parameters in community-dwelling healthy elderly adults. The participants were required to stand still in bipedal and unipedal stances on a force plate. Then, electromyography (EMG) was recorded from the tibialis anterior (TA) and medial and lateral gastrocnemius (MG/LG) muscles, and intermuscular coherence was calculated between the following pairs: TA and MG (TA–MG), TA and LG (TA–LG), and MG and LG (MG–LG). Furthermore, gait speed, unipedal stance time, and muscle mass were measured. EMG–EMG coherence for the MG–LG pair was significantly greater in the unipedal stance task than in the bipedal one (p = .001). Multiple linear regression analysis revealed that the muscle mass of the leg was negatively correlated with the change in the β-band coherence for the MG–LG pair from bipedal to unipedal stance (R² = 0.067, standard β = −0.345, p = .044). As the β-band coherence could reflect the corticospinal activity, the increased β-band coherence may be a compensation for the smaller muscle mass, or alternatively may be a sign of changes in the nervous system resulting in the loss of muscle mass.     

Social cognitive predictors of competitive level among athletes with physical disabilities

ObjectiveTo test a model of Social Cognitive Theory variables for predicting participation in higher versus lower levels of parasport competition. Information on modifiable factors associated with parasport competition would help parasport coaches and organizations transition recreational and developmental-level athletes to more competitive streams of participation.DesignCross-sectional survey.MethodParticipants were 95 parasport athletes with physical disabilities that cause mobility impairment (74% male; mean age = 34.36 ± 12.41). Measures of Social Cognitive Theory constructs were assessed via online questionnaires. Path analysis was used to test the proposed model.ResultsThe model explained 12% of the variance in level of sport participation. Peer support for sport was a significant predictor of self-regulatory efficacy (β = .22, p < .05) which, in turn, was positively related to outcome expectations (β = .43, p < .001), and self-regulation (β = .43, p < .001). Self-regulatory efficacy was the only significant predictor of level of sport participation (β = .26, p < .05). There were no significant indirect effects between social support and competitive status (p > .05).DiscussionSocial Cognitive Theory provides a reasonable basis for formulating a model of psychosocial factors related to parasport competitive status. Other relevant factors should be taken into consideration in subsequent studies. Parasport coaches and organizations may benefit from leveraging peer support to help bolster athletes' self-regulatory efficacy to levels conducive to participation in higher competitive sport streams.     

Everyday tasks impair spatiotemporal variables of gait in older adults with Parkinson's disease

IntroductionAlthough it is known that individuals with Parkinson's disease (PD) have difficulties performing dual-task activities, most of the studies have verified the effect of dual tasks on gait using tasks that are uncommon to perform while walking. However, the realization of tasks involving gait that really represents the daily activities carried out by the participants, allow us to detect real fall risk situations of individuals with PD during their gait.ObjectiveOur aim was to verify the influence of daily-life dual-tasks on gait spatiotemporal variables of the older adults with PD.Methods20 older adults without PD and 20 older adults with PD participated in the study. Gait kinematic was analyzed under three different conditions: walking without dual task, walking carrying bags with weight, and walking talking on the cell phone.ResultsOlder adults with PD presented lower speed (p = .001), cadence (p = .039), and shorter step length (p = .028) than older adults without PD during walking without dual tasks. When walking while carrying bags with weight, older adults with PD had a lower speed (p < .001), cadence (p = .015), shorter step length (p = .008), and greater double support time (p = .021) compared with older adults without PD. During walking while talking on the cell phone, older adults with PD walked with lower speed (p < .001), cadence (p = .013), shorter step length (p = .001) and swing time (p = .013), and increased double support time (p = .008) and support time (p = .014) in relation to older adults without PD.ConclusionDaily-life dual tasks impair the spatiotemporal variables of gait in the older adults with PD, which was most evident during walking talking on the cell phone.     

Differential effects of stimulus characteristics during knee joint perturbation on hamstring and quadriceps reflex responses

When stretching muscles of the ankle joint, stretch velocity and amplitude were shown to selectively influence specific parts of the stretch reflex. The present study investigated whether similar effects can be observed at the knee joint. Seventeen subjects were exposed to sudden anterior tibial translations. The influence of stimulus amplitude was analyzed by applying a low (LIMP) or high impulse (HIMP). To investigate the influence of velocity, rate of force development of the perturbation was chosen either low (LRFD) or high (HRFD). Activation of biceps femoris (BF), semitendinosus (ST), vastus medialis (VM) and vastus lateralis (VL) was calculated in four consecutive timeframes (P0, P1, P2, P3). During P1, RFD (ST: p < .05; BF: p < .01; VM: p < .05; VL: p > .05) and during P2, impulse (ST: p < .05; BF: p < .01; VM: p < .01; VL: p < .01) did significantly influence reflex activation. The present study showed that stimulus characteristics influenced specific reflex components of knee joint muscles. As only hamstring muscles were stretched, whereas quadriceps was unloaded, it is concluded that different mechanisms like homonymous and heteronymous muscle afferents as well as joint and skin afferents might contribute to the reflex responses.     

Sleep disturbance and emotion dysregulation as transdiagnostic processes in a comorbid sample

Sleep disturbance and emotion dysregulation have been identified as etiologic and maintaining factors for a range of psychopathology and separate literatures support their relationships to anxiety, depression, PTSD, and alcohol dependence (AD) symptom severity. Previous studies have examined these relationships in isolation, failing to account for the high rates of comorbidity among disorders. It is not yet known whether these processes uniquely predict symptom severity in each of these domains. Participants were 220 patients in residential substance abuse treatment, who had experienced a potentially traumatic event and exceeded screening cutoffs for probable PTSD and problematic alcohol use. Controlling for emotion dysregulation and the interrelationships among the outcome variables, insomnia was uniquely associated with anxiety (B = .27, p < .001), depression (B = .25, p < .001), PTSD (B = .22, p < .001), and AD (B = .17, p = .01) symptom severity. Similarly, controlling for insomnia, emotion dysregulation was uniquely associated with anxiety (B = .40, p < .001), depression (B = .47, p < .001), PTSD (B = .38, p < .001), and AD (B = .26, p < .001) symptom severity. Insomnia and emotion dysregulation appear to be transdiagnostic processes uniquely associated with symptom severity across a number of different domains and might be important treatment targets for individuals with PTSD and AD.     

Similar changes in muscle fiber phenotype with differentiated consequences for rate of force development: Endurance versus resistance training

Resistance training has been shown to positively affect the rate of force development (RFD) whereas there is currently no data on the effect of endurance training on RFD. Subjects completed ten weeks of either resistance training (RT, n = 7) or endurance cycling (END, n = 7). Pre and post measurements included biopsies obtained from m. vastus lateralis to quantify fiber phenotype and fiber area and isokinetic dynamometer tests to quantify maximal torque (Nm) and RFD (Nm/s) at 0–30, 0–50, 0–100 and 0–200 ms during maximal isometric contraction for both knee extensors and flexors. Both groups increased the area percentage of type IIa fibers (p < .01) and decreased the area percentage of type IIx fibers (p = .05), whereas only RT increased fiber size (p < .05). RT significantly increased eccentric, concentric and isometric strength for both knee extensors and flexors, whereas END did not. RT increased 200 ms RFD (p < .01) in knee flexor RFD and a tendency towards an increase at 100 ms (p < .1), whereas tendencies towards decreases were observed for the END group at 30, 50 and 100 ms (p < .1), resulting in RT having a higher RFD than END at post (p < .01). In conclusion, resistance training may be very important for maintaining RFD, whereas endurance training may negatively impact RFD.     

Comparative study of the differences in shoulder muscle activation according to arm rotation angle

BackgroundScapular muscle exercise is important for patients with shoulder disorders. Distal variance leads to changes in shoulder muscle activation. Here, we aimed to determine whether scapular muscle activation is affected by different arm rotation angles.MethodsOverall, 30 healthy men participated in this study. The subjects were asked to keep their arms at 120 degrees of shoulder flexion while holding a 1.0-kg dumbbell in palms down (pronation) and palms up (supination) positions. Electromyography was used to measure anterior, middle, posterior deltoid, serratus anterior, upper, and lower trapezius muscle activation during the task. The muscle activations of each shoulder were compared between the pronation and supination positions.ResultsAnterior deltoid and serratus anterior activations were significantly higher in supination than in pronation (p < .05). Alternatively, posterior deltoid and lower trapezius muscles were significantly more activated in pronation than in supination (p < .05).ConclusionScapular muscle activation changed with arm rotation angle. Arm rotation angle should be assessed to estimate scapular muscle activation during exercise and motion analysis in clinical practice.     

How many creatives are enough? Exploring how manipulating the number of creative players in the opposing team impacts footballers' performance during small-sided games

This study explored how varying the number of creative opponents affects youth players' performance during football small-sided games (SSGs). Initially, 60 players from 3 different age groups with n = 20 in each (under-9, U9; under-11, U11; and under-13, U13) were tested during SSGs to rank them according to their creative potential. Based on these rankings, four players shown to possess with a medium creative potential were assigned to the intermediate team for each age group. This team competed against a team on which players with high creative potential were progressively included (from one to finally all four players, 1C to 4C) during a 4-a-side plus goalkeeper SSG. The results showed that U9 players increased the individual space explored when facing more creative opponents (p = .012), while the U11 (p = .026) and U13 (p < .001) only increased when facing 2C and 3C. Playing against more creative opponents induced more variability in the distance to own (p = .046) and the opponent team's centroid (p = .046) in the U9, regularity in the U11 (team centroid, p < .001; opponents' centroid, p = .001) and lower regularity in the U13 (team centroid, p = .013 opponents' centroid, p = .009). These distinct movement patterns seemed to reflect the differences in players' perceptual and motor skills. A higher creative score was found against 1C (vs 2C and 4C, p = .006) and 3C (vs 4C, p = .006) in the U9. The results from the effect sizes indicated higher values on the players' attempts, fluency and versatility when facing 1C to 3C, whereas a clear decrease was observed against 4C for all age groups. Hence, moderate and high demanding scenarios prompt the emergence of new behaviours while extremely high demanding scenarios (i.e. 4C) seem to constrain all the creativity components. Overall, adding creative players mostly impacts the team's collective behaviour rather than the players' creativity-related skills.     

Associations among bullying role behaviors and academic performance over the course of an academic year for boys and girls

Although some research has evidenced a negative association between involvement in bullying and academic performance, more work is needed to understand the associations between academic performance and involvement in a more comprehensive range of bully role behaviors. The goals of the current study were to determine (a) the associations among a broader range of bully role behaviors (i.e., bullying, assisting, victimization, defending, and outsider behavior) and academic performance (i.e., grade point average; GPA), and (b) gender differences within these associations. The current study investigated these issues over the course of an academic year with 7794 students in middle through high school. Bullying behaviors were assessed in the fall and GPA data were gathered from school records from the spring of the same academic year. The results identified significant negative associations between bullying (b = −0.07, p = .001), assisting (b = −0.16, p < .001), victimization (b = −0.06, p < .001), and defending (b = −0.04, p < .001) with student GPA, whereas no significant association emerged for outsider behavior and GPA (b = −0.02, p = .13). In addition, several gender differences were found in these associations, including a stronger negative association between assisting and GPA for girls (b = −0.23, p = .001) than for boys (b = −0.08, p = .014) and a significant negative association between victimization and GPA for girls (b = −0.09, p < .001), but not boys (b = −0.02, p = .117). Differences in results across schools were also examined in an exploratory manner. The educational impact associated with bullying behaviors, limitations of the current study, and suggestions for future research are discussed.     

The effect of the driving activity on target detection as a function of the visibility level: Implications for road lighting

The Small Target Visibility model used in road lighting design is based on a strong simplification of the driving task. To specify the driver’s visibility needs in a way consistent with state-of-the-art lighting engineering practice, a field experiment was designed in order to investigate target detection performances, comparing driver and passenger status conditions. Sixteen target visibility levels (VL) were used. In the driver status, 34 participants had to press a button as soon as they detected the target stimulus placed on the experimental lighted section. In the passenger status, the same participants had to detect the target stimulus while the experimenter drove. The results show that the passengers’ performances (detection distance) were higher than the drivers’ performances (p = .0014). Furthermore, the higher the VL, the higher the detection distance (p < .0001). These results lead up to modify the reference scenario in order to take into account human factor components for road lighting design.     

The effects of lemon taste on attention,perceived exertion,and affect during a stepping task

ObjectivesTo better understand the effects of taste cues on delaying the attention shift from an external focus (dissociative) towards an internal focus (associative) as exercise intensity increases.DesignA between subjects' experimental design with random assignment to three groups: taste (lemon-flavored mouth guards), placebo (unflavored mouth guards), or control group (no mouth guards) was used. Participants reported perceived exertion, affect (i.e., pleasantness and arousal), and attention allocation before, during, and after performing a weighted stepping task.ResultsPerforming the task resulted in a gradual increase of perceived exertion, F (1.87, 74.89) = 63.05, p < .05, η_p² = .61, along with a shift from dissociative to associative attention, F (2.17, 86.68) = 35.57, p < .05, η_p² = .47 across all conditions. Additionally, participants reported feeling less pleasant and more aroused after task completion in all conditions. The lemon-flavored mouth guard failed to affect attention, F (4.33, 86.68) = 1.41, p = .23, η_p² = .07, perceived exertion, F (3.74, 74.86) = .38, p = .81, η_p² = .02, pleasantness, F (2, 40) = .126, p = .88, η_p² = .01, and arousal, F (2, 40) = 2.40, p = .10, η_p² = .10, differently than the other two conditions.ConclusionsThe study was one of the first to examine the effects of taste during an exertive task. Despite the non-significant effects of using a lemon-taste mouth guard on various cognitive variables (perception of exertion, attention allocation, pleasantness, and arousal), more scientific effort is needed to explore the effects of other tastes (e.g., sweet, bitter) and delivery methods (e.g., sprays, drops).     

Long-term efficacy of exercise across diagnostically heterogenous mental disorders and the mediating role of affect regulation skills

BackgroundExercise interventions are efficacious in reducing disorder-specific symptoms in various mental disorders. However, little is known about long-term transdiagnostic efficacy of exercise across heterogenous mental disorders and the potential mechanisms underlying treatment effects.MethodsPhysically inactive outpatients, with depressive disorders, anxiety disorders, insomnia or attention deficit hyperactivity disorder were randomized to a standardized 12-week exercise intervention, combining moderate exercise with behavior change techniques (BCTs) (n = 38), or a passive control group (n = 36). Primary outcome was global symptom severity (Symptom Checklist-90, SCL-90-R) and secondary outcomes were self-reported exercise (Physical Activity, Exercise, and Sport Questionnaire), exercise-specific affect regulation (Physical Activity-related Health Competence Questionnaire) and depression (SCL-90-R) assessed at baseline (T1), post-treatment (T2) and one year after post-treatment (T3). Intention-to-treat analyses were conducted using linear mixed models and structural equations modeling.ResultsFrom T1 to T3, the intervention group significantly improved on global symptom severity (d = −0.43, p = .031), depression among a depressed subsample (d = −0.62, p = .014), exercise (d = 0.45, p = .011) and exercise-specific affect regulation (d = 0.44, p = .028) relative to the control group. The intervention group was more likely to reveal clinically significant changes from T1 to T3 (p = .033). Increases in exercise-specific affect regulation mediated intervention effects on global symptom severity (ß = −0.28, p = .037) and clinically significant changes (ß = −0.24, p = .042).ConclusionsThe exercise intervention showed long-term efficacy among a diagnostically heterogeneous outpatient sample and led to long-lasting exercise behavior change. Long-term increases in exercise-specific affect regulation within exercise interventions seem to be essential for long-lasting symptom reduction.     

Local muscle oxygen consumption related to external and joint specific power

The purpose of the present study was to examine the effects of external work rate on joint specific power and the relationship between knee extension power and vastus lateralis muscle oxygen consumption (mVO₂). We measured kinematics and pedal forces and used inverse dynamics to calculate joint power for the hip, knee and ankle joints during an incremental cycling protocol performed by 21 recreational cyclists. Vastus lateralis mVO₂ was estimated using near-infrared spectroscopy with an arterial occlusion. The main finding was a non-linear relationship between vastus lateralis mVO₂ and external work rate that was characterised by an increase followed by a tendency for a levelling off (R² = 0.99 and 0.94 for the quadratic and linear models respectively, p < 0.05). When comparing 100 W and 225 W, there was a ∼43 W increase in knee extension but still a ∼9% decrease in relative contribution of knee extension to external work rate resulting from a ∼47 W increase in hip extension. When vastus lateralis mVO₂ was related to knee extension power, the relationship was still non-linear (R² = 0.99 and 0.97 for the quadratic and linear models respectively, p < 0.05). These results demonstrate a non-linear response in mVO₂ relative to a change in external work rate. Relating vastus lateralis mVO₂ to knee extension power showed a better fit to a linear equation compared to external work rate, but it is not a straight line.     

Psychological need satisfaction and thwarting: A test of Basic Psychological Needs Theory in physical activity contexts

ObjectivesTo test Basic Psychological Needs Theory (BPNT; Deci & Ryan, 2002) to determine if psychological need thwarting experienced when physically active contributes to the understanding of well-being and ill-being.Design/methodParticipants (N = 155, 67.70% female, M_age = 37.46 years; SD_age = 19.89 years) completed assessments of psychological need satisfaction and thwarting, subjective vitality and positive/negative affect during separate testing sessions separated by 6 months.ResultsScores from the modified version of the Psychological Need Thwarting Scale (PNTS-PA; Bartholomew, Ntoumanis, Ryan, & Thøgersen-Ntoumani, 2011) demonstrated discriminant evidence of validity, evidence of internal structure and minimal error variance. Changes in psychological need satisfaction positively predicted positive affect (R² = .16, p < .05), subjective vitality (R² = .13, p < .05) and negatively predicted negative affect (R² = .12, p < .05). Additional regression analyses revealed that changes in psychological need thwarting predicted negative affect (ΔR² = .11, p < .05), but not positive affect (ΔR² = .01, p > .05) or subjective vitality (ΔR² = .04, p > .05) beyond contributions made by psychological need satisfaction.ConclusionsOverall, these results extend the potential utility of the PNTS-PA as an instrument for use with BPNT beyond sport and support Deci and Ryan's (2002) contentions regarding the critical role of psychological need thwarting.