Your trial underscores how common diaphragmatic dysfunction and balance impairments are after stroke. What types of respiratory and postural difficulties do patients most frequently present with in the subacute and chronic stages? 

The diaphragmatic thickness on the affected side is reported to be around 50 per cent of the non-affected side during the subacute and chronic stages after stroke. 

This often leads to reduced inspiratory capacity, inefficient breathing patterns and reduced exercise capacity. 

Reported balance control impairments in stroke survivors frequently include diminished trunk control and postural asymmetry. 

The role of the diaphragm, which is central to the coupling of breathing and core stability, remains under-recognised and insufficiently addressed in conventional rehabilitation programs. 

This study is the first to test inspiratory muscle training (IMT) with a postural challenge in a randomised design. What led your team to explore unstablesurface training and what gaps in current respiratory rehabilitation were you aiming to address? 

The diaphragm plays a dual role in both respiration and postural control. 

Conventional respiratory rehabilitation has primarily focused on the respiratory effects of IMT, leaving a clear knowledge gap regarding the diaphragm’s postural function. 

As we were conducting the first randomised trial to test IMT with an added postural challenge, we sought to provide proof-of-concept that dual-task training of the diaphragm—incorporating an unstablesurface challenge into an IMT protocol— can enhance functional outcomes beyond IMT alone. 

The results show substantially greater improvements in lung function, diaphragm thickness and trunk control with unstable IMT compared with traditional IMT. Which components of the unstable-surface protocol do you believe most contributed to these larger effects? 

We attribute the larger effects to the progressive instability challenge, which elevates the centre of mass, narrows the base of support and modifies somatosensory input from the buttocks or plantar surfaces—thereby optimising diaphragmatic adaptation over the fourweek training period. 

Additionally, the protocol’s simplicity supported strong participant compliance. 

Walking endurance and quality of life improved meaningfully only in the unstable IMT group. How do you think changes in respiratory and trunk function translated into broader gains in mobility and everyday participation? 

While IMT typically targets respiratory gains, those improvements translate to broader function when they are sufficiently large and accompanied by better trunk control. 

In our unstable-surface IMT group, the substantial increases in diaphragm strength and symmetry likely enhanced ventilatory efficiency and oxygen delivery during activity, reducing exertional limitation. 

Simultaneously, dual-task diaphragm training improved trunk stability and intraabdominal pressure control, supporting gait, balance and turning. 

Together, these changes can increase mobility confidence, reduce compensatory effort and enable greater participation, as reflected in the observed gains in walking endurance and quality of life. 

Some outcomes—particularly certain centre-of-pressure measures and Timed Up and Go performance— showed intermediate or mixed results. How should clinicians interpret these findings when incorporating IMT into practice? 

The mixed findings suggest that IMT, particularly unstable IMT, should be viewed as a targeted adjunct rather than a standalone balance intervention. 

The observed improvements indicate benefits primarily in trunk stability and postural control under seated or low‑demand conditions that closely reflect the training context. 

However, transfer to more complex dynamic tasks should not be assumed. 

Clinically, unstable IMT may be most appropriate for individuals in the early stages after stroke or those with limited standing tolerance or impaired trunk control. 

To achieve improvements in dynamic balance, such as limits of stability and mobility outcomes, unstable IMT should be combined with task‑specific functional training, including centre of gravity displacement, sit‑to‑stand and gait and turning practice. 

These findings support integrating IMT within a broader, function‑oriented rehabilitation program. 

If you could design the next phase of research, what key questions about long-term training, progression of instability or mechanisms of action would you prioritise to strengthen the evidence base for IMT in stroke rehabilitation? 

Future studies should determine the long-term dose-response by defining how training duration, frequency and maintenance schedules influence both the magnitude and durability of benefits over time. 

The next phase of research should investigate the progression of instability—advancing from seated instability to standing and dynamic postural challenges—to better engage core stability demands, leverage the diaphragm’s dual role in respiration and trunk stabilisation and potentially amplify transfer to functional mobility. 

We are presently considering the feasibility of mechanistic monitoring, such as functional near-infrared spectroscopy, to investigate the relationship between neural and respiratory–trunk control adaptations to functional outcomes. 

>>William Tsang is a physiotherapy professor specialising in dual-tasking and mind-body exercise. He studies how cognitive-motor demands and practices such as tai chi and breathing/ postural training affect balance, gait and function, using objective measures to inform rehabilitation.