Peak patellar tendon force progressions during heavy load single-leg squats on level ground and decline board.

BACKGROUND: Progressive tendon loading programs for patellar tendinopathy typically include single-leg squats with heavy weights either on level ground or on a decline board. Changes in patellar tendon force due to variations of the heavy load single-leg squat have not yet been objectively quantified. The objective of this study was to investigate the influence of the mass of an external weight and the use of a decline board on the peak patellar tendon force during a heavy load single-leg squat. METHODS: Twelve healthy participants performed single-leg back squats on a decline board and level ground at 70%, 80% and 90% of their one repetition maximum. Three-dimensional kinematics and ground reaction forces were measured and the peak patellar tendon force was calculated using musculoskeletal modelling. A two-way repeated measures ANOVA determined the main effects for the mass of the external weights and the use of a decline board as well as their interaction effect. FINDINGS: Peak patellar tendon forces were significantly higher on the decline board compared to level ground (p < 0.05). Neither on the decline board, nor on level ground did the peak patellar tendon force increase significantly when increasing the external weights (p > 0.05). INTERPRETATION: Progression in peak patellar tendon forces during a heavy load single-leg squat can only be obtained with a decline board. Increasing the mass of the external weight from 70% to 90% of the one repetition maximum does not result in a progressively higher peak patellar tendon force.

External weight mass and carrying position influence peak patellar tendon force and patellofemoral joint contact force independently during forward lunge.

BACKGROUND: The forward lunge is a common exercise in the rehabilitation of patellar tendinopathy and patellofemoral pain syndrome. External weights are frequently used to increase the peak patellar tendon force and patellofemoral joint contact force during this exercise. The weight's position might influence this relationship. The objective of this study was to investigate the combined effect of an external weight's mass and carrying position on the peak patellar tendon force and patellofemoral joint contact force during a forward lunge. METHODS: Ten healthy individuals performed forward lunges holding external weights between 0.1 and 0.3 times body mass either in one hand at the ipsilateral or contralateral side of the leading leg, or in two hands at the side or in front of the trunk. Three-dimensional kinematic data and ground reaction forces were collected and peak patellar tendon force and patellofemoral joint contact force were calculated using musculoskeletal modelling. Two-way repeated measures ANOVA's determined the main effects for the external weight's mass and position as well as their interaction effect. FINDINGS: Increasing the mass of the external weights increased both the peak patellar tendon force and patellofemoral joint contact force linearly and at the same rate in all positions. Both peak forces were larger in the one-hand ipsilateral and two-hand side positions. INTERPRETATION: An external weight's mass and position both influence the peak patellar tendon force and patellofemoral joint contact force during a forward lunge. The rate of increase in peak forces with increasing mass was similar for all weight-carrying positions.

Increasing Step Frequency Reduces Patellofemoral Joint Stress and Patellar Tendon Force Impulse More at Low Running Speed.

PURPOSE: Patellofemoral pain syndrome and patellar tendinopathy are important running-related overuse injuries. This study investigated the interaction of running speed and step frequency alterations on peak and cumulative patellofemoral joint stress (PFJS) and patellar tendon force (PTF) parameters. METHODS: Twelve healthy individuals completed an incremental running speed protocol on a treadmill at habitual, increased and decreased step frequency. Peak PFJS and PTF, peak rate of PFJS and PTF development, and PFJS and PTF impulse per kilometer (km) were calculated using musculoskeletal modeling. RESULTS: With increasing running speed, peak PFJS ( P < 0.001) and PTF ( P < 0.001) and peak rate of PFJS ( P < 0.001) and PTF ( P < 0.001) development increased, whereas PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per km decreased. While increasing step frequency by 10%, the peak PFJS ( P < 0.001) and PTF ( P < 0.001) and the PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per kilometer decreased. No significant effect of step frequency alteration was found for the peak rate of PFJS ( P = 0.008) and PTF ( P = 0.213) development. A significant interaction effect was found for PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per km, suggesting that step frequency alteration was more effective at low running speed. CONCLUSIONS: The effectiveness of step frequency alteration on PFJS and PTF impulse per km is dependent on the running speed. With regard to peak PFJS and PTF, step frequency alteration is equally effective at low and high running speeds. Step frequency alteration was not effective for peak rate of PFJS and PTF development. These findings can assist the optimization of patellofemoral joint and patellar tendon load management strategies.

The effect of myofascial and physical therapy on trunk, shoulder, and elbow movement patterns in women with pain and myofascial dysfunctions after breast cancer surgery: Secondary analyses of a randomized controlled trial.

INTRODUCTION: Secondary upper limb dysfunctions are common after breast cancer treatment. Myofascial treatment may be a valuable physical therapy modality for this problem. OBJECTIVE: To investigate the effect of myofascial therapy in addition to physical therapy on shoulder, trunk, and elbow movement patterns in women with pain and myofascial dysfunctions at the upper limb after breast cancer surgery. DESIGN: A double-blinded randomized controlled trial. SETTING: Rehabilitation unit of a university hospital. PARTICIPANTS: Forty-eight women with persistent pain after finishing breast cancer treatment. INTERVENTIONS: Over 3 months, all participants received a standard physical therapy program. The experimental (n = 24) and control group (n = 24) received 12 additional sessions of myofascial therapy or placebo therapy, respectively. MAIN OUTCOME MEASURES: Outcomes of interest were movement patterns of the humerothoracic joint, scapulothoracic joint, trunk, and elbow, measured with an optoelectronic measurement system during the performance of a forward flexion and scaption task. Statistical parametric mapping (SPM) analyses were used for assessing the effect of treatment on movement patterns between both groups (group × time interaction effect). RESULTS: A significantly decreased protraction and anterior tilting was found after experimental treatment. No beneficial effects on movement patterns of the humerothoracic joint, trunk, or elbow were found. CONCLUSION: Myofascial therapy in addition to a 12-week standard physical therapy program can decrease scapular protraction and anterior tilting (scapulothoracic joint) during arm movements. Given the exploratory nature of these secondary analyses, the clinical relevance of these results needs to be investigated further.

A lab-based comparison of differential ratings of perceived exertion between a run and jump protocol involving low or high impacts on the lower extremities.

The rating of perceived exertion method (RPE) allows to describe training intensity in a single value. To better understand the underlying components, the separate rating of perceived breathlessness (RPE-B) and leg-muscle exertion (RPE-L) has been proposed. Here we hypothesised that the separation between the two components may (partly) be determined by the impacts on the lower extremities. In this study, we aimed to experimentally evaluate the differential effect of high versus low impact running and jumping on RPE-B and RPE-L in team sport activities by manipulating the movement strategy (heel strike and passive landing pattern versus forefoot strike and active landing pattern). Eighteen recreational team sport players participated in two submaximal tests consisting of a sequence of running and jumping bouts, whilst ground reaction forces (GRF) were collected. RPE-B and RPE-L data were collected after each bout using the CR100 scale. Paired-samples t-tests were used to analyse between-session differences in these variables. GRF analysis showed that absorption mechanics differed considerably between the two sessions. RPE-L was on average 6.50 AU higher in the low impact session (p = 0.006). However, RPE-B was also increased by 4.96 AU with low impact (p = 0.009). We conclude that the extent to which the lower extremities are being exposed to high or low impacts does not explain a possible separation between the two RPE types.HighlightsThe separate rating of the different underlying components of RPE (e.g. variables related to the cardiorespiratory and the muscular system) may provide more insight in the relationship between training load and training outcomes, which likely differs between these components.The findings of this study do not support the idea that the separation in rating between perceived breathlessness (RPE-B, cardiorespiratory) and leg-muscle exertion (RPE-L, muscular) is also rooted in the extent to which musculoskeletal structures in the lower extremities are being exposed to high or low impacts.

Postural balance strategies during landing at the moment of return-to-sports after anterior cruciate ligament reconstruction.

Most athletes that return to sport (RTS) after Anterior Cruciate Ligament (ACL) injury undergo reconstruction (ACLR) to restore their knee stability. The major concern for RTS is for the patient to be able to perform challenging dynamic tasks whilst adequately stabilizing the knee joint and maintaining their postural balance. Nevertheless, the interaction between knee protective mechanisms (such as knee unloading and knee stabilisation) and postural balance strategies has not yet been comprehensively analyzed. Thus, the aim of this study was to investigate landing balance strategies in ACLR athletes at time of RTS. Twenty-one athletes with a unilateral ACLR were tested at the time of RTS while performing a single leg hop for distance on both limbs. Three balance mechanisms that influence the GRF during the landing phase (foot placement, center of pressure (CoP) excursion, counter-rotation of segments) were investigated and compared between the ACL injured and uninjured limb. Interactions between knee protective mechanisms and postural balance strategies were tested using a statistical parametric mapping regression analysis. Results show that CoP excursions in the injured limb increased, as well as ankle joint moment contribution to anterior-posterior (A-P) GRF. Besides, patients presenting reduced knee joint contribution to A-P GRF had to compensate with higher hip joint contribution in order to maintain postural balance. In conclusion, ACLR athletes who at RTS still protect their reconstructed knee are forced to employ compensatory postural balance strategies. Therefore, there is a persistent trade-off between knee protection and postural balance at the moment of RTS.

Push-Off Dynamics Reveal Task-Independent Alterations in Athletes Returning to Sport after ACL Reconstruction.

PURPOSE: Athletes with an anterior cruciate ligament (ACL) reconstruction (ACLR) show persisting biomechanical and neuromuscular landing alterations. So far, most research focused on the landing phase of dynamic tasks where most ACL injuries occur. This study will assess whether these landing alterations are also present in the propulsion phase, in an attempt to identify generalized movement alterations. METHODS: Twenty-one athletes with ACLR (cleared by their surgeon and/or physiotherapist for return-to-sport) and twenty-one controls performed five single-leg hop tasks. Propulsion kinematics, kinetics, and muscle activations were compared between legs and between groups. RESULTS: Increased hamstrings activation was found during propulsion when comparing the ACLR limb with both the uninjured limb and the controls. In addition, decreased internal knee extension moments were found in the ACLR limb compared with the uninjured limb. CONCLUSIONS: Athletes with ACLR show task-independent alterations that unload the knee during the propulsion phase of single-leg hopping tasks. If longitudinal data deem these alterations to be maladaptive, more emphasis must be placed on their normalization during the propulsion phase, assuming beneficial carryover effects into the landing phase. Normalizing these patterns during rehabilitation may potentially reduce the risk of long-term complications such as reinjuries and posttraumatic osteoarthritis.