Connective Adaptive Resistance Exercise (CARE) Machines for Accentuated Eccentric and Eccentric-Only Exercise: Introduction to an Emerging Concept

Abstract

Eccentric resistance exercise emphasizes active muscle lengthening against resistance. In the past 15 years, researchers and practitioners have expressed considerable interest in accentuated eccentric (i.e., eccentric overload) and eccentric-only resistance exercise as strategies for enhancing performance and preventing and rehabilitating injuries. However, delivery of eccentric resistance exercise has been challenging because of equipment limitations. Previously, we briefly introduced the concept of connected adaptive resistance exercise (CARE)—the integration of software and hardware to provide a resistance that adjusts in real time and in response to the individual’s volitional force within and between repetitions. The aim of the current paper is to expand this discussion and explain the potential for CARE technology to improve the delivery of eccentric resistance exercise in various settings. First, we overview existing resistance exercise equipment and highlight its limitations for delivering eccentric resistance exercise. Second, we describe CARE and explain how it can accomplish accentuated eccentric and eccentric-only resistance exercise in a new way. We supplement this discussion with preliminary data collected with CARE technology in laboratory and non-laboratory environments. Finally, we discuss the potential for CARE technology to deliver eccentric resistance exercise for various purposes, e.g., research studies, rehabilitation programs, and home-based or telehealth interventions. Overall, CARE technology appears to permit completion of eccentric resistance exercise feasibly in both laboratory and non-laboratory environments and thus has implications for researchers and practitioners in the fields of sports medicine, physiotherapy, exercise physiology, and strength and conditioning. Nevertheless, formal investigations into the impact of CARE technology on participation in eccentric resistance exercise and clinical outcomes are still required.

Overview of muscle fatigue differences between maximal eccentric and concentric resistance exercise

“…2,3 New ECC resistance exercise technologies advance some of the limitations of isokinetic dynameters, permitting independent maximal strength assessments and exercise prescriptions for the CON and ECC phases of resistance exercises. [4][5][6][7] Thus, findings from the current review have potential implications for resistance exercise prescriptions that incorporate such equipment or isokinetic dynamometry to deliver CON or ECC resistance exercise.…”

“…Maximal ECC strength assessments are challenging to administer with traditional resistance exercise equipment but emerging technologies appear to make these assessments more feasible. [4][5][6][7] Thus, exercise prescriptions based on the ECC maximum might be more common in the future, and the %1RM-repetition relationship should not be assumed to be the same for ECC and CON resistance exercise.…”

“…Results from the current overview provide practical implications for resistance exercise prescriptions, particularly as ECC resistance exercise seems to have increased in popularity in recent years and given that there has been an emergence of exercise equipment to facilitate ECC resistance exercise prescriptions. 4,7,75 Skeletal muscles are approximately 40% stronger during ECC than CON muscle actions, 18 cardiovascular stress and perceptions of effort are lower during ECC than CON resistance exercise at equal absolute workloads, [61][62][63][64][65][66]76 and weeks of ECC resistance exercise increases muscle size and strength. 1,[77][78][79][80][81] Thus, ECC resistance exercise is believed to be an effective way for improving health and fitness in healthy adults as well as in older adults and those who have medical conditions that might require an exercise stimulus with less cardiovascular stress and lower perceptions of effort.…”

“…Historically, the ability to complete sets of repeated ECC or CON exercise was limited to isokinetic dynamometers, which, although regularly used by researchers, 1 have not been widely adopted by strength and conditioning coaches, 2,3 and are rarely found in fitness centers. New exercise technologies [4][5][6][7] have potential to make completion of submaximal and maximal ECC or CON resistance exercise more feasible outside of the laboratory. Thus, increased participation in these modes of resistance exercise, particularly ECC, is anticipated in the future, and the acute physiological responses to such exercise should be understood to guide exercise prescriptions.…”

Resistance Exercise Minimal Dose Strategies for Increasing Muscle Strength in the General Population: an Overview

“…A likely reason that eccentric resistance exercise has not received more attention in previous discussions on minimal dose strategies is that traditional resistance exercise equipment (e.g., free weights, plate-loaded machines, and weight stack machines) is not conducive to performing eccentric resistance exercise [ 118 ]. Exercising with such equipment involves use of the same load in the eccentric and concentric phases, which probably does not maximize dose potency.…”