Peak muscle activation, joint kinematics, and kinetics during elliptical and stepping movement pattern on a Precor Adaptive Motion Trainer

Effects of and Response to Mechanical Loading on the Knee

Mechanical loading to the knee joint results in a differential response based on the local capacity of the tissues (ligament, tendon, meniscus, cartilage, and bone) and how those tissues subsequently adapt to that load at the molecular and cellular level. Participation in cutting, pivoting, and jumping sports predisposes the knee to the risk of injury. In this narrative review, we describe different mechanisms of loading that can result in excessive loads to the knee, leading to ligamentous, musculotendinous, meniscal, and chondral injuries or maladaptations. Following injury (or surgery) to structures around the knee, the primary goal of rehabilitation is to maximize the patient's response to exercise at the current level of function, while minimizing the risk of re-injury to the healing tissue. Clinicians should have a clear understanding of the specific injured tissue(s), and rehabilitation should be driven by knowledge of tissue-healing constraints, knee complex and lower extremity biomechanics, neuromuscular physiology, task-specific activities involving weight-bearing and non-weight-bearing conditions, and training principles. We provide a practical application for prescribing loading progressions of exercises, functional activities, and mobility tasks based on their mechanical load profile to knee-specific structures during the rehabilitation process. Various loading interventions can be used by clinicians to produce physical stress to address body function, physical impairments, activity limitations, and participation restrictions. By modifying the mechanical load elements, clinicians can alter the tissue adaptations, facilitate motor learning, and resolve corresponding physical impairments. Providing different loads that create variable tensile, compressive, and shear deformation on the tissue through mechanotransduction and specificity can promote the appropriate stress adaptations to increase tissue capacity and injury tolerance. Tools for monitoring rehabilitation training loads to the knee are proposed to assess the reactivity of the knee joint to mechanical loading to monitor excessive mechanical loads and facilitate optimal rehabilitation.

Effects of Impact Versus Non-impact Cardiovascular Machines in Individuals between Age 50 and 80 Years

Older adults are at increased risk of injury when initiating exercise due to inactivity, functional limitation, illness, or fall risk. We studied a novel non-impact cardio unit in an effort to determine whether there were differences in physiologic, functional, and strength benefits compared to a treadmill (TM), while producing less stress on the knee and lessening the risk of fall and injury. Utilizing a prospective, randomized, non-blinded, cohort design, individuals aged 50–80 years were recruited and enrolled in a 16-week exercise program. Subjects were randomly allocated to either exercise on the Cybex arc trainer or on a TM. Participants exercised for 120 min per week. Resistance was adjusted to achieve a target RPE in each group. Functional, strength, and physiologic markers were analyzed through balance testing, ten – repetition max leg press, body composition analysis, and lipid panel results. Overall health-related quality of life was also measured. There was a significant improvement in triglyceride and very low density lipoprotein levels from baseline to exit within the arc trainer group. An equal and significant increase in strength capacity was observed in both the arc trainer and TM groups, as were feelings of increased energy, improved emotional well-being, and decreased fatigue. Leg strength increased, percentage of body fat decreased, and balance improved following use of either an arc trainer or a TM in a study population of 58 participants over a 16-week period. This study demonstrated that positive change occurs, physiologically and psychologically when an arc trainer or TM is utilized. Given the similar benefits seen in this study, use of a non-impact modality such as the arc trainer may be a better alternative in the older population.

The effects of a standard elliptical vs. a modified elliptical with a converging footpath on lower limb kinematics and muscle activity

Elliptical trainers that increase the inter-pedal distance may have potential benefits for knee osteoarthritis by decreasing the amount of knee varus. Modifying elliptical trainers with a converging footpath and reduced inter-pedal distance may be beneficial for reducing anterior knee pathology risk by decreasing knee valgus angles. Twenty-one college students participated in a single testing session. Participants exercised on two different elliptical trainers, one modified with a converging footpath and reduced inter-pedal width, and a standard elliptical trainer. Participants exercised for 2 min at three ramps incline at 120 strides per minute and constant work rate. Three-dimensional kinematics and electromyography of the dominant lower limb were recorded. Multiple 2 × 3 (Elliptical x Incline) ANOVAs with Bonferroni corrections were used to compare the two elliptical trainers at each incline for kinematics and muscle activity. The modified elliptical trainer displayed significantly decreased peak knee valgus (p = 0.031, η p 2 = 0.234 ), peak knee flexion (p = 0.006, η p 2 = 0.246 ), and interactions for peak knee flexion (p = 0.001, η p 2 = 0.250 ) and vastus lateralis (p < 0.01, η p 2 = 0.380 ) muscle activity compared to the standard elliptical trainer. The decreased peak knee valgus and flexion angles could be beneficial for reducing long-term injury risk for anterior knee pathologies.

Comparison of knee biomechanical characteristics during exercise between pinnacle and step trainers

BACKGROUND

A novel stair-climber called a pinnacle trainer (PT) provides both sagittal and frontal plane exercise, making it different from a step trainer (ST), which provides only sagittal plane exercise. Exercise with different trajectories may produce different biomechanical responses. There are currently no guidelines for choosing between a PT and a ST for different training or rehabilitation purposes.

RESEARCH QUESTIONS

Are there differences in the electromyographic patterns of lower extremity musculature and biomechanical responses of the knee joint during exercise between using a PT and a ST?

METHODS

This study utilizes a prospective observational study design. Eighteen healthy males participated in the study. A six-axis force and torque transducer embedded in the machine pedal synchronized with a three-dimensional motion capture system were utilized to measure kinematic and kinetic data of the right knee during the stepping movement. The activities of six lower extremity muscles of the same limb were captured with surface electromyography during exercise on the two trainer types.

RESULTS

The co-activation index of the vastus lateralis (VL) and the biceps femoris (BF) recorded during ST exercise was significantly greater than that for the PT exercise. Moreover, exercise using the ST produced a significantly greater knee downward force compared to that for the PT. Exercise with the PT produced a significantly greater internal knee varus moment compared to that for the ST.

SIGNIFICANCE

The ST provided greater co-activation of the BF and VL and a greater knee joint downward force, which may decrease the antero-posterior displacement of the tibia relative to the femur. Exercise with the PT produced a significant internal knee varus moment and a more balanced muscular activation on the vastus medialis and VL compared to that for the ST, which may decrease the maltracking of the patella.

Knee joint biomechanics in transtibial amputees in gait, cycling, and elliptical training

Transtibial amputees may experience decreased quality of life due to increased risk of knee joint osteoarthritis (OA). No prior studies have compared knee joint biomechanics for the same group of transtibial amputees in gait, cycling, and elliptical training. Thus, the goal of this study was to identify preferred exercises for transtibial amputees in the context of reducing risk of knee OA. The hypotheses were: 1) knee biomechanics would differ due to participant status (amputee, control), exercise, and leg type (intact, residual) and 2) gait kinematic parameters would differ due to participant status and leg type. Ten unilateral transtibial amputee and ten control participants performed exercises while kinematic and kinetic data were collected. Two-factor repeated measures analysis of variance with post-hoc Tukey tests and non-parametric equivalents were performed to determine significance. Maximum knee compressive force, extension torque, and abduction torque were lowest in cycling and highest in gait regardless of participant type. Amputee maximum knee extension torque was higher in the intact vs. residual knee in gait. Amputee maximum knee flexion angle was higher in the residual vs. intact knee in gait and elliptical. Gait midstance knee flexion angle timing was asymmetrical for amputees and knee angle was lower in the amputee residual vs. control non-dominant knees. The results suggest that cycling, and likely other non-weight bearing exercises, may be preferred exercises for amputees due to significant reductions in biomechanical asymmetries and joint loads.

Lower Limb Joint Angular Position and Muscle Activity During Elliptical Exercise in Healthy Young Men

The purpose of this study was to compare lower extremity joint angular position and muscle activity during elliptical exercise using different foot positions and also during exercise on a lateral elliptical trainer. Sixteen men exercised on a lateral elliptical and on a standard elliptical trainer using straight foot position, increased toe-out angle, and a wide step. Motion capture and electromyography systems were used to obtain 3D lower extremity joint kinematics and muscle activity, respectively. The lateral trainer produced greater sagittal and frontal plane knee range of motion (ROM), greater peak knee flexion and extension, and higher vastus medialis activation compared with other conditions (P < .05). Toe-out and wide step produced the greatest and smallest peak knee adduction angles, respectively (P < .05). The lateral trainer produced greater sagittal and frontal plane hip ROM and greater peak hip extension and flexion compared with all other conditions (P < .05). Toe-out angle produced the largest peak hip external rotation angle and lowest gluteus muscle activation (P < .05). Findings from this study indicate that standard elliptical exercise with wide step may place the knee joint in a desirable frontal plane angular position to reduce medial knee loads, and that lateral elliptical exercise could help improve quadriceps strength but could also lead to larger knee contact forces.

Clinical Implications of Changing Parameters on an Elliptical Trainer

BACKGROUND

Specific weightbearing instructions continue to be a part of routine orthopaedic clinical practice on an injured or postoperative extremity. Researchers and clinicians have struggled to define the best weightbearing strategies to maximize clinical outcomes.

PURPOSE

To investigate the average percentage body weight (APBW) values, weightbearing distribution percentages (WBDP), and cadence values on the entire foot, hindfoot, and forefoot during changing resistance and incline on an elliptical trainer, as well as to suggest clinical implications.

STUDY DESIGN

Descriptive laboratory study.

METHODS

An original research study was performed consisting of 30 asymptomatic subjects (mean age, 29.54 ± 12.64 years; range, 21-69 years). The protocol included 3 consecutive tests of changing resistance and incline within a speed range of 70 to 95 steps/min. The SmartStep weightbearing gait analysis system was utilized to measure the values.

RESULTS

The APBW values for the entire foot ranged between 70% and 81%, the hindfoot values were between 27% and 57%, and the forefoot values between 42% and 70%. With regard to WBDP, the forefoot remained planted on the pedal (stance phase) 2 to 3 times more as compared with the hindfoot raise in the swing phase.

CONCLUSION

The study findings highlight the fact that elliptical training significantly reduces weightbearing in the hindfoot, forefoot, and entire foot even at higher levels of resistance and incline.

CLINICAL RELEVANCE

Weightbearing on the hindfoot consistently displayed the lowest weightbearing values. Orthopaedic surgeons, now equipped with accurate weightbearing data, may recommend using the elliptical trainer as a weightbearing exercise early on following certain bony or soft tissue pathologies and lower limb surgical procedures.