Selective activation of lower leg muscles during maximum voluntary isometric contractions

The pronators and supinators play a key role in the medio-lateral stability of the ankle joint complex (i.e. talo-crural and subtalar joints). We hypothesized that each shank muscle has a specific activation pattern determined by its anatomical course around the axes of the subtalar and talo-crural joints. A secondary objective was to examine the effect of foot posture on these activation patterns. Forty-nine young adults (25 normal-arched feet, 24 flat-arched feet) performed maximum voluntary isometric contractions against manual resistance in four movement directions: plantarflexion (PF), dorsiflexion (DF), pronation (PRO) and supination (SUP). Electromyographic activity was recorded from tibialis posterior (TP) and peroneus longus (PL) with intramuscular electrodes, and gastrocnemius medialis (GM) and tibialis anterior (TA) with surface electrodes. When compared to their agonist function, all muscles were co-activated at significantly lower levels in their synergistic function (GM: 23% during SUP, TA: 72% during SUP; TP: 42% during PF, PL: 52% during PF) (p < 0.001). A significant interaction between foot posture and contraction type was evident for TA. During isometric contractions, the electromyographic activity of the shank muscles is geared to their biomechanical advantage according to their position relative to the subtalar and talo-crural joint axes.     

Applying an active lumbopelvic control strategy during lumbar extension exercises: Effect on muscle recruitment patterns of the lumbopelvic region

ObjectiveExamine whether implementing an active lumbopelvic control strategy during high load prone lumbar extension exercises affects posterior extensor chain recruitment and lumbopelvic kinematics.MethodsThirteen healthy adults acquired an optimal active lumbopelvic control strategy during guided/home-based training sessions. During the experimental session electromyography was used to evaluate the activity of the posterior extensor chain muscles during high load trunk/bilateral leg extension exercises with/without application of the strategy. Video-analysis was used to evaluate thoracic/lumbar/hip angles.ResultsImplementing the active lumbopelvic control strategy decreased the lordotic angle during trunk (p = 0.045; −3.2°) and leg extension exercises (p = 0.019; −10°). The hip angle was solely affected during trunk extension (p < 0.001; +9.2°). The posterior extensor chain (i.e. mean of the relative activity of all muscles (%MVIC) was recruited to a higher extent (p = 0.026; +9%) during trunk extension exercises performed with active lumbopelvic control. Applying the strategy during leg extension exercises lead to less activity of longissimus thoracic (p = 0.015; −10.2%) and latissimus dorsi (p = 0.010; −4.4%), and increased gluteus maximus activity (p ≤ 0.001; +16.8%).ConclusionsWhen healthy people are taught/instructed to apply an active lumbopelvic control strategy, this will decrease the degree of lumbar (hyper)lordosis and this influences the recruitment patterns of trunk and hip extensors. Hence, the possible impact on predetermined training goals should be taken into account by trainers.     

Modulation of motor variability related to experimental muscle pain during elbow-flexion contractions

Experimental muscle pain typically reorganizes the motor control. The pain effects may decrease when the three-dimensional force components are voluntarily adjusted, but it is not known if this could have negative consequences on other structures of the motor system. The present study assessed the effects of acute pain on the force variability during sustained elbow flexion when controlling task-related (one-dimensional) and all (three-dimensional) contraction force components via visual feedback. Experimental muscle pain was induced by bolus injection of hypertonic saline into m. biceps brachii, and isotonic saline was used as control. Twelve subjects performed sustained elbow flexion at different levels of the maximal voluntary contraction (5–30% MVC) before, during, and after the injections. Three-dimensional force components were measured simultaneously with surface electromyography (EMG) from elbow flexors and auxiliary muscles. Results showed that force variability was increased during pain compared to baseline for contractions using one-dimensional feedback (P < .05), but no significant differences were found for three-dimensional feedback. During painful contractions (1) EMG activity from m. trapezius was increased during contractions using both one-dimensional and three-dimensional feedback (P < .05), and (2) the complexity of EMG from m. triceps brachii and m. deltoid was higher for the three-dimensional feedback (P < .05). In conclusion, the three-dimensional feedback reduced the pain-related functional distortion at the cost of a more complex control of synergistic muscles.     

Functioning of peripheral Ia pathways in leg muscles of newly walking toddlers

Monosynaptic and polysynaptic spinal level reflexes in the leg muscles of infants show significant dispersion across muscles, high variability, and no change in response patterns over the first 10 months. Here we tested the hypothesized relation between early walking experience and the tuning of these responses in three primary gait muscles of participants in four subgroups: cruisers (n = 7) and toddlers with one (n = 5), two (n = 5), or three (n = 5) months of walking experience. Reflex responses in multiple Ia pathways – tendon reflex (T-reflex), vibration-induced inhibition of the T-reflex (VIM-T-reflex), and tonic vibration-induced reflex (VIR), were elicited by mechanical stimuli applied to the distal tendons of the quadriceps, gastrocnemius-soleus, and tibialis anterior of both legs. Walking skill was assessed via a GAITRite mat. Generally, walking experience seemed to be related to slowly emerging improvements and, depending on muscle tested and pathway, progress was quite varied. Amplitude and latency of reflex responses were more clearly impacted by age or leg length while the ratio or distribution pattern of reflex response among antagonist pairs of muscles was impacted by walking experience and skill. As walking experience increased, the ratio of reflex responses tended to increase for the stimulated and decrease for the antagonist reflex loops with distribution of the pattern shifting gradually toward a single type of reflex response in all tested muscles. The very slow tuning of these reflexes may underlie the many missteps and falls reported to occur during early walking and suggest that subsequent studies should continue to follow the developmental trajectory through the first year of walking experience.     

Gastrocnemius and soleus are selectively activated when adding knee extensor activity to plantar flexion

The gastrocnemius is a biarticular muscle that acts not only as a plantar flexor, but also as a knee flexor, meaning that it is an antagonist during knee extension. In contrast, the soleus is a monoarticular plantar flexor. Based on this anatomical difference, these muscles’ activities should be selectively activated during simultaneous plantar flexion and knee extension, which occur during many activities of daily living. This study examined the selective activation of gastrocnemius and soleus activities when voluntary isometric activation of knee extensors was added to voluntary isometric plantar flexion. Ten male volunteers performed isometric plantar flexion at 10%, 20%, and 30% of maximum effort. During each plantar flexion task, isometric knee extension was added at 0%, 50%, and 100% of maximum effort. When knee extension was added, the average rectified value of the electromyographic activity of the medial gastrocnemius was significantly depressed (P = .002), whereas that of the soleus was significantly increased (P < .001) regardless of the plantar flexion level. These results suggest that plantar flexion with concurrent knee extensor activity leads to selective activation of the soleus and depression of the synergistic activity of the gastrocnemius.     

Reduced cortical voluntary activation during bilateral knee extension

IntroductionReduced neural drive is mainly thought to explain the bilateral deficit phenomenon, i.e. the difference in maximal isometric voluntary contraction (MVC) between unilateral and bilateral contractions. The aim of the present study was to further document if bilateral knee extension is associated with changes in voluntary activation level assessed by both peripheral nerve electrical stimulation and transcranial magnetic stimulation.MethodsFourteen subjects performed unilateral and bilateral knee extensions with both superimposed femoral electrical nerve stimulation and transcranial magnetic stimulation in order to assess voluntary activation (VA_FNES) and cortical voluntary activation (VA_TMS), respectively.ResultsThere was no difference in MVC force of the tested leg when involved in unilateral and bilateral knee extensions (p = 0.87). However, a significantly reduced VA_FNES (−2.1 ± 2.4%; p = 0.01) and VA_TMS (−1.6 ± 2.7%; p = 0.04) have been evidenced during bilateral knee extension.DiscussionIt is hypothesized that counterbalances could have masked the decrease of voluntary activation during bilateral contraction.     

Fatigue-induced dissociation between rate of force development and maximal force across repeated rapid contractions

We examined whether the presence of fatigue induced by prolonged running influenced the time courses of force generating capacities throughout a series of intermittent rapid contractions. Thirteen male amateur runners performed a set of 15 intermittent isometric rapid contractions of the knee extensor muscles, (3 s/5 s on/off) the day before (PRE) and immediately after (POST) a half marathon. The maximal voluntary contraction force, rate of force development (RFD_peak), and their ratio (relative RFD_peak) were calculated. At POST, considering the first (out of 15) repetition, the maximal force and RFD_peak decreased (p < 0.0001) at the same extent (by 22 ± 6% and 24 ± 22%, respectively), resulting in unchanged relative RFD_peak (p = 0.6). Conversely, the decline of RFD_peak throughout the repetitions was more pronounced at POST (p = 0.02), thus the decline of relative RFD_peak was more pronounced (p = 0.007) at POST (−25 ± 13%) than at PRE (−3 ± 13%). The main finding of this study was that the fatigue induced by a half-marathon caused a more pronounced impairment of rapid compared to maximal force in the subsequent intermittent protocol. Thus, the fatigue-induced impairment in rapid muscle contractions may have a greater effect on repeated, rather than on single, attempts of maximal force production.     

Explanatory models of muscle performance in acromegaly patients evaluated by knee isokinetic dynamometry: Implications for rehabilitation

PurposeTo evaluate the effects of demographics and hormonal variations on knee muscle performance in patients with acromegaly and develop explanatory models of peripheral muscle function in these individuals.MethodsThis was a cross-sectional study in which 53 acromegalics and 27 healthy subjects underwent knee isokinetic dynamometry to evaluate the peak torque value for leg extension at 75°/s (PTE75) and 240°/s (PTE240). Separate multivariable linear regression models for the prediction of PTE75 and PTE240 were tested using variables commonly used as predictors in the clinical setting and other specific variables related to acromegaly.ResultsThe final prediction model for PTE75 (R² = 0.888; adjusted R² = 0.820, SE of bias = 16.2 Nm, p < 0.001) was −0.221 × growth hormone + 36.791 × sex_male = 1 − 27.407 × status_active = 1 − 0.690 × age + 148.071. The final prediction model for PTE240 (R² = 0.816; adjusted R² = 0.805, SE of bias = 8.8 Nm, p < 0.001) was −0.174 × growth hormone + 12.522 × sex_male = 1 − 0.520 × age + 98.099.ConclusionsIn acromegalics, high growth hormone levels, female gender, and older age are associated with reduced muscle strength and endurance. Additionally, active disease negatively affects peripheral muscle strength in these patients.     

Muscle strength and functional performance is markedly impaired at the recommended time point for sport return after anterior cruciate ligament reconstruction in recreational athletes

PurposeTo examine potential deficits in muscle strength or functional capacity when comparing (1) an ACL reconstructed group to matched healthy controls, (2) the ACL reconstructed leg to the non-injured leg and (3) the non-injured leg to matched healthy controls, at the time-point of recommended sport return 9–12 months post-surgery.MethodsSixteen patients (male-female ratio: 9:7) 9–12 months post ACL reconstruction and sixteen age and sex matched healthy controls were included. Outcome measures included maximal knee extensor (KE) and knee flexor (KF) dynamometry, including measurement of rate of force development, functional capacity (counter movement jump (CMJ) and single distance hop (SDH)) and the Lysholm score.ResultsCompared to the control group, maximal KE and KF muscle strength were impaired in the ACL reconstructed leg by 27–39% and 16–35%, respectively (p < .001). Also, impairments of both CMJ (38%) and SDH (33%) were observed (p < .001). Rate of force development for KE were reduced in the ACL group compared to the control group (p < .001). Similarly, the KE and KF muscle strength, CMJ and SDH of the ACL reconstructed leg were impaired, when compared to the non-injured leg by 15–23%, 8–20%, 23% and 20%, respectively (p < .05).ConclusionMuscle strength and functional capacity are markedly impaired in the ACL reconstructed leg of recreationally active people 9–12 months post-surgery when compared to healthy matched controls and to their non-injured leg. This suggests that objective criteria rather than “time-since-surgery” criteria should guide return to sport.     

The Supraspinatus and the Deltoid – Not just two arm elevators

BackgroundThe debate on the clinical and functional role of the Supraspinatus in relation to the Deltoid necessitates experimental assessment of their contributions to arm elevation. Our goal was to evaluate the responses of both muscles to increased elevation moment loading.MethodsTwenty-three healthy volunteers applied 30 N elevation forces at the proximal and distal humerus, resulting in small and large glenohumeral elevation moment tasks. The responses of the Deltoid and Supraspinatus were recorded with surface and fine-wire electromyography, quantified by (EMG_distal − EMG_proximal), and normalized by the summed activations (EMG_distal + EMG_proximal) to R_Muscle ratios.ResultsDeltoid activity increased with large elevation moment loading (R_DE = .11, 95%-CI [.06–.16]). Surprisingly, there was no significant average increase in Supraspinatus activation (R_SSp = .06, 95%-CI [−.08 to .20]) and its response was significantly more variable (Levene’s test, F = 11.7, p < .001). There was an inverse association between the responses (ß = −1.02, 95%-CI [−2.37 to .32]), indicating a potential complementary function of the Supraspinatus to the Deltoid.ConclusionThe Deltoid contributes to the glenohumeral elevation moment, but the contribution of the Supraspinatus is variable. We speculate there is inter-individual or intra-muscular function variability for the Supraspinatus, which may be related to the frequently reported variations in symptoms and treatment outcome of Supraspinatus pathologies.     

How much does the human medial gastrocnemius muscle contribute to ankle torques outside the sagittal plane?

Ankle movements in the frontal plane are less prominent though not less relevant than movements in the plantar or dorsal flexion direction. Walking on uneven terrains and standing on narrow stances are examples of circumstances likely imposing marked demands on the ankle medio-lateral stabilization. Following our previous evidence associating lateral bodily sways in quiet standing to activation of the medial gastrocnemius (MG) muscle, in this study we ask: how large is the MG contribution to ankle torque in the frontal plane? By arranging stimulation electrodes in a selective configuration, current pulses were applied primarily to the MG nerve branch of ten subjects. The contribution of populations of MG motor units of progressively smaller recruitment threshold to ankle torque was evaluated by increasing the stimulation amplitude by fixed amounts. From smallest intensities (12–32 mA) leading to the firstly observable MG twitches in force-plate recordings, current pulses reached intensities (56–90 mA) below which twitches in other muscles could not be observed from the skin. Key results showed a substantial MG torque contribution tending to rotate upward the foot medial aspect (ankle inversion). Nerve stimulation further revealed a linear relationship between the peak torque of ankle plantar flexion and inversion, across participants (Pearson R > .81, p < .01). Specifically, regardless of the current intensity applied, the peak torque of ankle inversion amounted to about 13% of plantar flexion peak torque. Physiologically, these results provide experimental evidence that MG activation may contribute to stabilize the body in the frontal plane, especially under situations of challenged stability.     

Postural stability with exhaustive repetitive sit-to-stand exercise in young adults

Previous research has indicated that muscle fatigue due to repeated bouts of physical activity can have negative residual effects on balance; however investigations using multi-joint forms of exercise involved in everyday settings and determination of how control of posture is altered during the physical activity itself are limited. The purpose of this investigation was to evaluate alterations in postural stability before, during, and after prolonged multi-joint STS exercise in healthy young adults. Center of pressure (COP) acquisitions were collected during repetitive STS exercise, while voluntary limits of stability (LOS) testing was performed before, immediately after, and 10 min after STS exercise. By 50% total STS exercise time, fatigue resulted in increased anterio-posterior (y) and medio-lateral (x) COP path lengths (p = 0.003 and p = 0.018 respectively) and an anterior shift of COP at seat-off towards the mid-foot (p = 0.010). No significant change in LOS mean amplitude was found after STS exercise; however a significant fatigue effect resulted in increased COPy sway velocity at maximal lean positions (p = 0.006), but returned to PRE values after 10 min of rest. Declines in postural stability during repetitive STS exercise was associated with reduced control of COP, as well as a reduced ability to stably control COP at extreme postural limits; however, 10 min was adequate in young adults for recovery. These results may have important implications for monitoring fall risk due to acute bouts of exercise induced muscle fatigue from repetitive multi-joint activities such as the STS.     

Partial body weight support treadmill training speed influences paretic and non-paretic leg muscle activation,stride characteristics,and ratings of perceived exertion during acute stroke rehabilitation

BackgroundIntensive task-specific training is promoted as one approach for facilitating neural plastic brain changes and associated motor behavior gains following neurologic injury. Partial body weight support treadmill training (PBWSTT), is one task-specific approach frequently used to improve walking during the acute period of stroke recovery (<1 month post infarct). However, only limited data have been published regarding the relationship between training parameters and physiologic demands during this early recovery phase.ObjectiveTo examine the impact of four walking speeds on stride characteristics, lower extremity muscle demands (both paretic and non-paretic), Borg ratings of perceived exertion (RPE), and blood pressure.DesignA prospective, repeated measures design was used.MethodsTen inpatients post unilateral stroke participated. Following three familiarization sessions, participants engaged in PBWSTT at four predetermined speeds (0.5, 1.0, 1.5 and 2.0 mph) while bilateral electromyographic and stride characteristic data were recorded. RPE was evaluated immediately following each trial.ResultsStride length, cadence, and paretic single limb support increased with faster walking speeds (p ⩽ 0.001), while non-paretic single limb support remained nearly constant. Faster walking resulted in greater peak and mean muscle activation in the paretic medial hamstrings, vastus lateralis and medial gastrocnemius, and non-paretic medial gastrocnemius (p ⩽ 0.001). RPE also was greatest at the fastest compared to two slowest speeds (p < 0.05).ConclusionsDuring the acute phase of stroke recovery, PBWSTT at the fastest speed (2.0 mph) promoted practice of a more optimal gait pattern with greater intensity of effort as evidenced by the longer stride length, increased between-limb symmetry, greater muscle activation, and higher RPE compared to training at the slowest speeds.     

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.     

Time and direction preparation of the long latency stretch reflex

This study investigated time and direction preparation of motor response to force load while intending to maintain the finger at the initial neutral position. Force load extending or flexing the index finger was given while healthy humans intended to maintain the index finger at the initial neutral position. Electromyographic activity was recorded from the first dorsal interosseous muscle. A precue with or without advanced information regarding the direction of the forthcoming force load was given 1000 ms before force load. Trials without the precue were inserted between the precued trials. A long latency stretch reflex was elicited by force load regardless of its direction, indicating that the long latency stretch reflex is elicited not only by muscle stretch afferents, but also by direction-insensitive sensations. Time preparation of motor response to either direction of force load enhanced the long latency stretch reflex, indicating that time preparation is not mediated by afferent discharge of muscle stretch. Direction preparation enhanced the long latency stretch reflex and increased corticospinal excitability 0–20 ms after force load when force load was given in the direction stretching the muscle. These enhancements must be induced by preset of the afferent pathway mediating segmental stretch reflex.     

Corticomotor excitability of gluteus maximus and hip extensor strength: The influence of sex

PurposeTo compare hip extensor strength and corticomotor excitability (CME) of gluteus maximus (GM) between males and females. A secondary purpose was to determine if CME of GM is predictive of hip extensor strength.MethodThirty-two healthy individuals participated (15 males and 17 females). CME of GM was assessed using the input-output curve (IOC) procedure acquired from transcranial magnetic stimulation (average slope). Hip extensor strength was measured by a dynamometer during a maximal voluntary isometric contraction. Independent t-tests were used to compare CME of GM and peak hip extensor torque between males and females. Linear regression analysis was used to determine whether peak hip extensor torque was predicted by CME of GM.ResultCompared to males, females demonstrate lower peak hip extensor torque (4.42 ± 1.11 vs. 6.15 ± 1.72 Nm/kg/m2, p < 0.01) and lower CME of GM (1.36 ± 1.07 vs. 2.67 ± 1.30, p < 0.01). CME of GM was a significant predictor of peak hip extensor torque for males and females combined (r² = 0.36, p < 0.001).ConclusionOur findings support the premise that corticomotor excitability plays a role in the ability of a muscle to generate torque.     

Evidence of muscular adaptations within four weeks of barbell training in women

We investigated the time course of neuromuscular and hypertrophic adaptations associated with only four weeks of barbell squat and deadlift training. Forty-seven previously untrained women (mean ± SD, age = 21 ± 3 years) were randomly assigned to low volume training (n = 15), moderate volume training (n = 16), and control (n = 16) groups. The low and moderate volume training groups performed two and four sets, respectively, of five repetitions per exercise, twice a week. Testing was performed weekly, and included dual X-ray absorptiometry and vastus lateralis and rectus femoris B-mode ultrasonography. Bipolar surface electromyographic (EMG) signals were detected from the vastus lateralis and biceps femoris during isometric maximal voluntary contractions of the leg extensors. Significant increases in lean mass for the combined gynoid and leg regions for the low (+0.68 kg) and moderate volume (+0.47 kg) groups were demonstrated within three weeks. Small-to-moderate effect sizes were shown for leg lean mass, vastus lateralis thickness and pennation angle, and peak torque, but EMG amplitude was unaffected. These findings demonstrated rapid muscular adaptations in response to only eight sessions of back squat and deadlift training in women despite the absence of changes in agonist–antagonist EMG amplitude.     

Comparison of trunk muscle reflex activation patterns between active and passive trunk flexion–extension loading conditions

The aim of the present study was to determine the effects of trunk flexion–extension loading on the neuromuscular reflexive latencies and amplitude responses of the trunk musculature. Eighteen male and female subjects (18–27 yrs) participated in active and passive trunk flexion extension, performed ∼7 days apart. Subjects performed 60 trunk flexion–extension repetitions. Surface electromyography (EMG) was collected bilaterally from paraspinal and abdominal muscles. In the active condition, subjects volitionally moved their trunks, while in the passive condition the dynamometer controlled the movements. The trunk was perturbed before and immediately after 30 repetitions. Latency of muscle onset, latency of first peak, latency of maximum peak, and peak EMG amplitude were evaluated. No differences between conditions, sides, or perturbation session were apparent. Overall latencies were shorter in females (p < .05) and abdominal muscles compared to paraspinals (p < .05). Thoracic paraspinal muscle amplitudes were greater than all other muscles (p < .05). Based upon the present results, the neuromuscular system engages trunk flexor muscles prior to the paraspinals in order to provide possible stabilization of the trunk when flexor moments are generated. Overall, the results indicate no difference in response of the neuromuscular system to active or passive repetitive loading.     

Various shrug exercises can change scapular kinematics and scapular rotator muscle activities in subjects with scapular downward rotation syndrome

Scapular dyskinesis, characterized by scapular downward rotation syndrome (SDRS) affects scapula-humeral rhythm and results in shoulder dysfunction. Previous study has led to the recommendation of standard shrug exercise to contend with SDRS and strengthen the upper trapezius (UT) muscle. However, few researchers have examined which shrug exercise is most effective. The aim of this research was to compare scapular kinematic changes and scapular rotator muscles activity across three different shrug exercises in SDRS. The amounts of scapular downward rotation were measured by a caliper and the scapular upward rotation angle was measured using two digital inclinometers. Surface electromyography was used to measure EMG amplitude from the UT, lower trapezius (LT), serratus anterior (SA), and levator scapula (LS). Seventeen subjects with SDRS were recruited for this study. The subjects performed three shrug exercises with 30° shoulder abduction (preferred shrug, frontal shrug, and stabilization shrug). The stabilization shrug showed a significantly greater scapular upward rotation angle compared with the preferred shrug (P = 0.004) and frontal shrug (P = 0.006). The UT activity was significantly greater in the frontal shrug than in the preferred shrug (P = 0.002). The UT/LS muscle activity ratio was also significantly greater in the frontal shrug than in the preferred shrug (P = 0.004). The stabilization shrug should be preferred to enhance the upward rotation angle. In addition, the frontal shrug can be used as an effective method to increase UT activity and to decrease LS activity in SDRS.     

Social influence and physical activity in older females: Does activity preference matter?

BackgroundOlder adults appear to have different activity preferences (prefer to be active alone or with others, or show no preference). As the activity of older females is often associated with social influences (i.e., how others influence the behavior or thoughts of another), understanding how activity preference might interact with social influences becomes important.ObjectivesThis study explored whether activity preferences would moderate the social influence – physical activity relationship in older females.MethodsThe sample for this study was 102 older females with the majority (87%) classified as ‘maintainers’. Using a cross-sectional approach, participants completed questionnaires on social influences by channel (family, friends, healthcare workers) and type (modeling, compliance, conformity, obedience), activity preferences, and physical activity.ResultsMANOVA and follow-up results revealed that friends-modeling (F (2, 99) = 8.15, p < .01) and friends-compliance/conformity (F (2, 99) = 9.82, p < .01) were greater in individuals who preferred to be active with others than those who preferred to be active alone. Results from a hierarchical multiple regression examining activity preferences as a moderator were significant (R²_change = .11). For those who preferred to be active with others, friends-modeling was positively related to activity (b = 1.28). For individuals with no activity preference, activity was positively related to friends-compliance/conformity (b = 1.38) and negatively related to friends-modeling (b = ?1.56).ConclusionResults provide preliminary evidence that activity preferences appear to moderate the relationship between the influence of friends and activity in older females, especially for those who are activity maintainers.